This is an example of a HTML caption with a link.
Atomic Rocket
Sabtu, 01 Januari 2011
1 komentar
Engine List
On This Page
The RS 10 from Star Born by Andre Norton, 1957.Artwork by Dean Ellis. Judging from the size of the people, the ship is approximately 70 meters high (240 feet).
Introduction
There is a nice basic overview of propulsion systems here.
Jump to the Drive Table.
You can spend lots of time researching spacecraft propulsion systems. But you are in luck, I've got some data for you. Most of this is from Philip Eklund's out of print boardgame Rocket Flight, the impressive Spaceship Handbook, and the indispensable Space Propulsion Analysis and Design. The rest is from various places I found around the internet, and no, I didn't keep track of where I got them. Use at your own risk.
Philip Eklund has a new boardgame out called High Frontier, which has the Atomic Rockets seal of approval (be sure to get the expansion pack as well). It has even more cutting-edge but scientifically accurate propulsion systems, which will eventually find there way onto this web page. (more detailshere, here, here, and here.)
If you don't like the values in the table, do some research to see if you can discover values you like better. Also note that the designs in the list are probably optimized for high exhaust velocities at the expense of thrust. There is a chance that some can be altered to give enough thrust for lift-off at the expense of exhaust velocity. Or you can just give up and go beg Mr. Tyco Bass for some atomic tri-tetramethylbenzacarbonethylene. Four drops should do the trick.
Some engines require electricity in order to operate. These have their megawatt requirements listed under "Power Requirements". With these engines, the Engine Mass value includes the mass of the power plant (unless the value includes "+pp", which means the mass value does NOT include the mass of the power plant). The power plant mass can be omitted if the spacecraft relies on beamed power from a remote power station. Alas, I could find no figures on the mass of the power plant. If the plant is nuclear, it probably has a mass of around 0.5 to 10 tons per megawatt. I agree, that isn't much help. Sorry. Efficiency is the percentage of the power requirements megawatts that are actually turned into thrust. The rest becomes waste heat and has to be removed with heat radiators.
The only vaguely possible propulsion system that has both high exhaust velocity and high thrust is the Nuclear Salt Water Rocket, and not a few scientist have questions about its feasibility. Well, actually there is also Project Orion, but that has other problems (see below). In science fiction, one often encounters the legendary "fusion drive" or "torchship", which is a high exhaust velocity + high thrust propulsion system that modern science isn't sure is even possible.
Jump to the Drive Table.
You can spend lots of time researching spacecraft propulsion systems. But you are in luck, I've got some data for you. Most of this is from Philip Eklund's out of print boardgame Rocket Flight, the impressive Spaceship Handbook, and the indispensable Space Propulsion Analysis and Design. The rest is from various places I found around the internet, and no, I didn't keep track of where I got them. Use at your own risk.
Philip Eklund has a new boardgame out called High Frontier, which has the Atomic Rockets seal of approval (be sure to get the expansion pack as well). It has even more cutting-edge but scientifically accurate propulsion systems, which will eventually find there way onto this web page. (more detailshere, here, here, and here.)
If you don't like the values in the table, do some research to see if you can discover values you like better. Also note that the designs in the list are probably optimized for high exhaust velocities at the expense of thrust. There is a chance that some can be altered to give enough thrust for lift-off at the expense of exhaust velocity. Or you can just give up and go beg Mr. Tyco Bass for some atomic tri-tetramethylbenzacarbonethylene. Four drops should do the trick.
Some engines require electricity in order to operate. These have their megawatt requirements listed under "Power Requirements". With these engines, the Engine Mass value includes the mass of the power plant (unless the value includes "+pp", which means the mass value does NOT include the mass of the power plant). The power plant mass can be omitted if the spacecraft relies on beamed power from a remote power station. Alas, I could find no figures on the mass of the power plant. If the plant is nuclear, it probably has a mass of around 0.5 to 10 tons per megawatt. I agree, that isn't much help. Sorry. Efficiency is the percentage of the power requirements megawatts that are actually turned into thrust. The rest becomes waste heat and has to be removed with heat radiators.
T/W >1.0 = Thrust to Weight ratio greater than zero? This boils down to: can this engine be used to take off from Terra's surface? If the answer is "no" use it only for orbit to orbit maneuvers. It is calculated by figuring if the given thrust can accelerate the engine mass greater than one gee of acceleration. As a rule of thumb, a practical spacecraft capable of lifting off from the Earth's surface will require a T/W of about 50 to 75.
Most propulsion systems fall into two categories: SUV and economy. SUV propulsion is like an SUV automobile: big and muscular, but the blasted thing gets a pathetic three miles to the gallon. Economy propulsion has fantastic fuel economy, but has trouble climbing low hills. In the world of rockets, good fuel economy means a high "specific impulse" (Isp) and high exhaust velocity. And muscle means a high thrust.The only vaguely possible propulsion system that has both high exhaust velocity and high thrust is the Nuclear Salt Water Rocket, and not a few scientist have questions about its feasibility. Well, actually there is also Project Orion, but that has other problems (see below). In science fiction, one often encounters the legendary "fusion drive" or "torchship", which is a high exhaust velocity + high thrust propulsion system that modern science isn't sure is even possible.
Watch the Heat
Chart from "The Atomic Rocket" by L. R. Shepherd, Ph.D., B.Sc., A.Inst.P., & A. V. Cleaver, F.R.Ae.S., 1948. Collected in Realities of Space Travel
Magnetic Nozzle
Painting by Vincent Di Fate for the novelStarfire by Paul Preuss
Chart from "To The Stars" by Gordon Woodcock, (1983). Collected in Islands In The Sky, edited by Stanley Schmidt and Robert Zubrin (1996). Most of the engines on this chart are torchships.
Fp = (F * Ve ) / 2
where
- Fp = thrust power (watts)
- F = thrust (newtons)
- Ve = exhaust velocity (m/s)
Jerry Pournelle says (in his classic A STEP FARTHER OUT) that an exhaust velocity of 28,800,000 cm/s corresponds to a temperature of 5 million Kelvin.
As an exceedingly rough approximation:
Ae = (0.5 * Am * Av2) / B
where
- Ae = particle energy (Kelvin)
- Am = mass of particle (g) (1.6733e-24 grams for monatomic hydrogen)
- Av = exhaust velocity (cm/s)
- B = Boltzmann's constant: 1.38e-16 (erg K-1)
A slightly less rough approximation:
Qe = (Ve / (Z * 129))2 * Pw
where
- Qe = engine reaction chamber temperature (Kelvin)
- Ve = exhaust velocity (m/s)
- Z = heat-pressure factor, varies by engine design, roughly from 1.4 to 2.4 or so.
- Pw = mean molecular weight of propellant, 1 for atomic hydrogen, 2 for molecular hydrogen
Larry Niven postulates something like this in his "Known Space" series, the crystal-zinc tube makes a science-fictional force field which reflects all energy. Niven does not explore the implications of this. However, Niven and Pournelle do explore the implications in THE MOTE IN GOD'S EYE. The Langson Field is used in the ship's drive, and as a force screen defense. The Langson field absorbs energy, and can re-radiate it. As a defense it sucks up hostile laser beams and nuclear detonations. As a drive, it sucks up and contains the energy of a fusion reaction, and re-radiates the energy as the equivalent of a photon drive exhaust.
(And please remember the difference between "temperature" and "heat". A spark from the fire has a much higher temperature than a pot of boiling water, yet a spark won't hurt your hand at all while the boiling water can give you second degree burns. The spark has less heat, which in this context is the thrust power in watts.)
If one has no science-fictional force fields, as a rule of thumb the maximum heat load allowed on the drive assembly is around 5 MW/m2. This is the theoretical ultimate, for an actual propulsion system it will probably be quite a bit less. For a back of the envelope calculation:
Rc = 0.12 * sqrt[H]where
- Rc = reaction chamber radius (meters)
- H = reaction chamber waste heat (megawatts)
Example
Say your propulsion system has an exhaust velocity of 5.4e6 m/s and a thrust of 2.5e6 N. Now Fp=(F*Ve)/2 so the thrust power is 6.7e12 W. So, 6.7e12 watts divided by 1.0e6 watts per megawatt gives us 6.7e6 megawatts. Plugging this into the equation results in 0.12 * sqrt[6.7e6 MW] = drive chamber radius of 310 meters or a diameter of a third of a mile. Ouch.
Only use this equation if H is above 4,000 MW or so, and if the propulsion system is a thermal type (i.e., fission, fusion, or antimatter).
An alternative is an exhaust nozzle formed from a magnetic field. The metal framework lets the heat escape instead of vaporizing the nozzle. The magnetic field cannot be vaporized since it is composed of energy instead of matter.
And don't forget the Kzinti Lesson.
Calculating the performance of a spaceship can be complicated. But if the ship is powerful enough, we can ignore gravity fields. It is then fairly easy. The ship will accelerate to a maximum speed and then turn around and slow down at its destination. Fusion or annihilation-drive ships will probably do this. They will apply power all the time, speeding up and slowing down.(ed note: a"brachistochrone" trajectory)
In this simple case, all the important performance parameters can be expressed on a single graph. This one is drawn for the case when 90% of the starting mass is propellant. (ed note: a mass ratio of 10) Jet velocity (exhaust velocity) and starting acceleration are the graph scales. Distance for several bodies are shown. Mars varies greatly; I used 150 million kilometers. Trip times and specific power levels are also shown. "Specific power" expresses how much power the ship generates for each kilogram of its mass, that is, its total power divided by its mass. The propellant the ship will carry is not included in the mass value.
An example: Suppose your ship can produce 100 kW/kg of jet power. You wish to fly to Jupiter. Where the 100 kW/kg and Jupiter lines cross on the graph, read a jet velocity of 300,000 m/s (Isp = 30,000) and an initial acceleration of nearly 0.01g. Your trip will take about two months.
The upper area of the graph shows that high performance is needed to reach the nearest stars. Even generation ships will need, in addition to very high jet velocities, power on the order of 100 kW/kg. The space shuttle orbiter produces about 100 kW/kg with its three engines. The high power needed for starflight precludes its attainment with means such as electric propulsion.
In this simple case, all the important performance parameters can be expressed on a single graph. This one is drawn for the case when 90% of the starting mass is propellant. (ed note: a mass ratio of 10) Jet velocity (exhaust velocity) and starting acceleration are the graph scales. Distance for several bodies are shown. Mars varies greatly; I used 150 million kilometers. Trip times and specific power levels are also shown. "Specific power" expresses how much power the ship generates for each kilogram of its mass, that is, its total power divided by its mass. The propellant the ship will carry is not included in the mass value.
An example: Suppose your ship can produce 100 kW/kg of jet power. You wish to fly to Jupiter. Where the 100 kW/kg and Jupiter lines cross on the graph, read a jet velocity of 300,000 m/s (Isp = 30,000) and an initial acceleration of nearly 0.01g. Your trip will take about two months.
The upper area of the graph shows that high performance is needed to reach the nearest stars. Even generation ships will need, in addition to very high jet velocities, power on the order of 100 kW/kg. The space shuttle orbiter produces about 100 kW/kg with its three engines. The high power needed for starflight precludes its attainment with means such as electric propulsion.
- Gordon Woodcock
"Plasma Drives"
There are dozens of so-called "plasma drives" currently on the drawing board. Dr. John Schilling ranks them in order of decreasing reality:
- Hall Effect Thrusters (HET) (hundred-plus flown)
- Arcjets (dozens flown)
- Ion thrusters (dozens flown)
- Pulsed Plasma Thrusters (PPT) (a few flown)
- Magnetoplasmadynamic thrusters (MPD) (many ground tests)
- Microwave electrothermal thrusters (some ground tests)
- Field Emission Electrostatic Propulsion (some ground tests)
- Pulsed Inductive Thrusters (PIT) (few ground tests)
- VASIMR (none built, much analysis)
- M2P2 (none built, some analysis)
Popular Conceptions
These illustrations are from a 1963 Russian magazine called "Техника молодежи" magazine ("Technology Youth"), as shown in Pavel Popelskii's Science Illustration blog. They are more a popularization for children than they are a rigorous technical document, but they are interesting. I do not speak or read Russian, but I discovered that Google Translate is my friend. Any awkward phrasing is the fault of Google translate.
The rocket marked IV appears to be using a system of 'shock tubes', heating a working fluid then pulsing it out underpressure. However, this seems like it would be less efficient then simply operating the engine directly as an NTR, so i have my doubts. As Rob Davidoff pointed out, there is no addition of further "work" after the propellant is heated in the reactor.
"Isotopic motor"
"Isotopic motor" (a.k.a. fission sail.)
- 1. The radioactive isotope - a source of alpha particles.
- 2. Absorber of alpha particles, which protects the equipment from the particles emitted in a random direction.
- 3. Alpha particles.
This engine is labeled an "isotopic motor", but nowadays is called a fission sail. Radioactive material has its radiation absorbed on all sides except in the desired thrust direction. Great specific impulse, but the thrust is microscopic.
Nuclear-electric rocket
"Reactor", possibly a radioisotope thermoelectric generator.
- 4. Reactor.
- 5. Vacuum diode - a source of electrical current, working on the principle of thermionic emission.
- 6. Neutron reflector to their concentration in the reaction zone.
As near as I can figure, the spherical object labeled "reactor" is actually a typeRadioisotope Thermoelectric Generator. I say this because the section labeled "5" appears to be a thermocouple. The spacecraft appears to be a generalizedNuclear-Electric rocket. The unspecified engine would be some kind of electrical propulsion, like ion or plasma.
Magnetohydrodynamic power
Fission reactor and magnetohydrodynamic generator.
- 6. Neutron reflector to their concentration in the reaction zone.
- 7. Solenoid to produce a magnetic field.
- 8. Capacitor divider that separates the uranium from the hydrogen.
- 9. Hydrogen plasma, fed into accelerators.
- 10. Electrodes for the removal of the electric current created by the movement of plasma through a magnetic field.
- 11. The direction of electric current.
- 12. Zone of fission.
This uses a magnetohydrodynamic (MHD) generator to harvest electricity from the uranium-hydrogen plasma. The fissioning uranium ionizes the hydrogen. The ionized stream can conduct electricity. It is shot through a magnetic field (created by a solenoid), where it induces an electrical current in the side plates. The stream then enters the "divider" where the uranium is separated from the hydrogen. The unspent uranium is sent back to the reaction chamber. The hydrogen is sent to some kind of electromagnetic accelerator which is powered by the electricity from the MHD generator.
I have no idea if this will acually work, or if it was discredited decades ago. Up until now I had only seen MHD harvesting of electricity associated with nuclear fusion reactions, not nuclear fission.
The "reactor" is actually the reaction chamber (12). The "motor" is the electromagnetic accelerator. "Working mass" is another name for "reaction mass", "working fluid", or "propellant". The shadow shield is up near the nose, though generally it is more efficient to put it right on top of the reactor. The "vernier motor" is an attitude jet.
I have no idea if this will acually work, or if it was discredited decades ago. Up until now I had only seen MHD harvesting of electricity associated with nuclear fusion reactions, not nuclear fission.
The "reactor" is actually the reaction chamber (12). The "motor" is the electromagnetic accelerator. "Working mass" is another name for "reaction mass", "working fluid", or "propellant". The shadow shield is up near the nose, though generally it is more efficient to put it right on top of the reactor. The "vernier motor" is an attitude jet.
- 13. Nozzle.
- 14. Uranium-graphite reactor core.
Looks like every NERVA diagram I've ever seen. A nuclear reactor where the coolant flows directly to the exhaust.
- 6. Neutron reflector to their concentration in the reaction zone.
- 12. Zone of fission.
Uranium is just spraying into the reaction chamber along with the propellant. Easiest to engineer, but lots of expensive un-burnt uranium escapes out the exhaust. This angers the owner's accountants and the picketing anti-nuclear activists.
- 6. Neutron reflector to their concentration in the reaction zone.
- 12. Zone of fission.
- 15. Openings for supply of hydrogen in the tangential and the walls of the cylindrical chamber.
Uranium is injected tanjentally, to make a spiral flow around the long axis. Hopefully this forces the uranium to loiter in the reaction chamber longer, reducing the amount of un-burnt uranium that escapes.
D. Gas-core Open-Cycle NTR with Recirculation
- 6. Neutron reflector to their concentration in the reaction zone.
- 8. Capacitor divider that separates the uranium from the hydrogen.
- 12. Zone of fission.
I have never seen this one before.
By doing some research I stumbled over a paper on Russian gas-core design. There is a "recirculation intake" just before the exhaust nozzle that tries to catch the uranium before it escapes. The uranium is liquifed then pumped back to the top of the reaction chamber. Frankly I do not understand why the hot fissioning uranium does not instantly vaporize the intake scoop.
But that is not this design. In this one, the fissioning uranium is jetted in the contrary direction to the hydrogen propellant. It is captured at the top, the hydrogen is filtered out, and sent back to the bottom to be injected again. The author calls it a "coaxial gas reactor", but this is not the same thing as the coaxial-flow NTR.
By doing some research I stumbled over a paper on Russian gas-core design. There is a "recirculation intake" just before the exhaust nozzle that tries to catch the uranium before it escapes. The uranium is liquifed then pumped back to the top of the reaction chamber. Frankly I do not understand why the hot fissioning uranium does not instantly vaporize the intake scoop.
But that is not this design. In this one, the fissioning uranium is jetted in the contrary direction to the hydrogen propellant. It is captured at the top, the hydrogen is filtered out, and sent back to the bottom to be injected again. The author calls it a "coaxial gas reactor", but this is not the same thing as the coaxial-flow NTR.
- 6. Neutron reflector to their concentration in the reaction zone.
- 16. Molten uranium carbide.
- 17.Porous wall through which the hydrogen leak.
The uranium is liquid, and the reaction chamber is spun on the long axis to keep the uranium in the chamber by centrifugal force. Note the tiny arrow indicating the spin, it's a dead giveaway.
Fourth rocket engine (Fig. IV) works in a peculiar thermo-mechanical cycle. Part of the energy of the reactor is used to drive the pump, which feeds into the reactor core liquid working medium, where it vaporizes and heated at high pressure.
The resulting hot gas is pumped into a separate high-pressure chamber, which, through valve 11 communicates with tube shocks. At the other end of the shock tube we find structed diffuser serves to concentrate the energy of the shock wave, and the valve 12, connecting tube with a nozzle rocket. Duty cycle engine is as follows: pump 5 takes the working fluid from the reservoir and high-pressure pumps it through a reactor, where it evaporates and is heated to about 2500° C — and then injected into the high-pressure chamber. Shock tube at this point is still filled with gas of low pressure left over from the previous cycle. Then the valve 11 to quickly open, compressed gas, bursting into the pipe instantaneously compresses and heats the gas in the tube, causing the appearance in it of a strong shock wave.
The highest compression is achieved in the lower stream of the diffuser. Then, valve 11 closes and valve 12 opens and gas at high speed coming out of the nozzle. When the temperature of exhaust gas will decrease by 3-4 times compared with the maximum temperature reached in the shock tube, valve 12 closes and valve 13 opens, and by a pump 5 remains a shock tube fed into a radiator where it cools. This cycle is continuously repeated, creating "clusters" of high-temperature gas flowing from a nozzle at high speed.
The resulting hot gas is pumped into a separate high-pressure chamber, which, through valve 11 communicates with tube shocks. At the other end of the shock tube we find structed diffuser serves to concentrate the energy of the shock wave, and the valve 12, connecting tube with a nozzle rocket. Duty cycle engine is as follows: pump 5 takes the working fluid from the reservoir and high-pressure pumps it through a reactor, where it evaporates and is heated to about 2500° C — and then injected into the high-pressure chamber. Shock tube at this point is still filled with gas of low pressure left over from the previous cycle. Then the valve 11 to quickly open, compressed gas, bursting into the pipe instantaneously compresses and heats the gas in the tube, causing the appearance in it of a strong shock wave.
The highest compression is achieved in the lower stream of the diffuser. Then, valve 11 closes and valve 12 opens and gas at high speed coming out of the nozzle. When the temperature of exhaust gas will decrease by 3-4 times compared with the maximum temperature reached in the shock tube, valve 12 closes and valve 13 opens, and by a pump 5 remains a shock tube fed into a radiator where it cools. This cycle is continuously repeated, creating "clusters" of high-temperature gas flowing from a nozzle at high speed.
- NUCLEAR ROCKET by M. Viskova. Technology Youth magazine Jan. 1960
The Drive Table
Download the PDF version here
If these figures result in disappointing rocket performance, in the name of science fiction you can tweak some of them and claim it was due to a technological advance. You are allowed to tweak anything who's name does not end in "MAX". You can alter the Thrust, Engine Mass, and/or the Eff, but no other values. If there is a corresponding "MAX" entry for the engine you are tweaking, you cannot alter any of the values above the "MAX" entry (i.e., you are not allowed to tweak NTR-SOLID-DUMBO's thrust above 7,000,000, which is the value in the NTR-SOLID MAX entry).
The engines are sorted by thrust power, since that depends on both exhaust velocity and thrust. So engines that high in both of those parameters will be towards the end of the list. This is useful for designers trying to make spacecraft that can both blast-off from a planet's surface and do efficient orbital transfers.
If one was trying to design a more reasonable strictly orbit-to-orbit spacecraft one would want the engine list sorted by exhaust velocity. And surface-to-orbit designers would want the list sorted by thrust.
I have also created a graph of the data below.
| Propulsion System | Thrust Power (GWatts) | Exhaust velocity (m/s) | Thrust (newtons) | Engine mass (tons) | T/W >1.0 | Power req (MWatts) | Eff |
|---|---|---|---|---|---|---|---|
| Aluminum-Oxygen | 2,800 | ||||||
| Methane-Oxygen | 3,700 | ||||||
| Hydrogen-Oxygen | 4,500 | ||||||
| VASIMR (high gear) | 0.006 | 294,000 | 40 | 10+pp | no | 10 | 60% |
| VASIMR (med gear) | 0.006 | 147,000 | 80 | 10+pp | no | 10 | 60% |
| VASIMR (low gear) | 0.006 | 29,000 | 400 | 10+pp | no | 10 | 60% |
| ArcJet | 0.011 | 22,000 | 1000 | 15 | no | 30 | 48% |
| Monatomic-H MITEE | 0.015 | 12,750 | 2,350 | 0.2 | yes | ||
| Hybrid Electro-Thermal MITEE | 0.015 | 17,660 | 1,700 | 1-10 | no | ||
| AIM | 0.016 | 598,000 | 55 | ? | no | ||
| Solar Moth | 0.018 | 9,000 | 4,000 | 0.1 | no | Sunlight | 63% |
| Basic MITEE | 0.075 | 9,810 | 14,000 | 0.2 | yes | ||
| Colloid Electrostatic | 0.17 | 43,000 | 8000 | 20 | no | 200 | 85% |
| J x B Electric | 0.19 | 74,000 | 5,000 | 110 | no | 211 | 80% |
| NTR-SOLID (H2) | 8,093 | ||||||
| NTR-SOLID (CH4) | 6,318 | ||||||
| NTR-SOLID (NH3) | 5,101 | ||||||
| NTR-SOLID (H2O) | 4,042 | ||||||
| NTR-SOLID (CO2) | 3,306 | ||||||
| NTR-SOLID (CO or N2) | 2,649 | ||||||
| NTR-SOLID/NERVA | 0.198- 0.065 | see above | 49,000 | 10 | no | ||
| Laser Thermal | 0.065 | 40,000 | 13,000 | 20 | no | 920 laser | 30% |
| NTR-LIQUID/LARS | 0.2 | 19,620 | 20,000 | 1.0 | yes | ||
| Mass Driver | 0.3 | 30,000 | 20,000 | 150 | no | 350 | 90% |
| LANTR (Nerva mode) | 0.309 | 9,221 | 67,000 | ? | yes | ||
| LANTR (LOX mode) | 0.584 | 6,347 | 184,000 | ? | yes | ||
| Ion | 1.05 | 210,000 | 10,000 | 400 | no | 800 | 96% |
| D-T Fusion | 1.2 | 22,000 | 108,000 | 10 | yes | ||
| NTR-SOLID/NERVA Deriv (H2) | 1.35 | 8085 | 334,061 | 10.1 | yes | (1570) | |
| Metahelium He* | 1.4 | 43,000 | 64,000 | 10 | no | ||
| NTR-SOLID/PBed (H2) | 1.59 | 9,530 | 333,617 | 1.7 | yes | (1945) | |
| NTR-SOLID/CERMET (H2) | 2.03 | 9,120 | 445,267 | 9.0 | yes | (2000) | |
| AM-SOLID max | 2.4 | 10,791 | 440,000 | ? | yes | ||
| MPD | 3.1 | 314,000 | 20,000 | 1540 | no | 4000 | 79% |
| Chemical MAX | 3.8 | 4,500 | 1,669,000 | 2 | yes | ||
| Metahelium He IV-A | ? | 21,600 | ? | 10 | ? | ||
| AM-Gas max | ? | 24,500 | ? | ? | ? | ||
| NTR-GAS/Closed (H2) | 4.5 | 20,405 | 445,000 | 56.8 | no | ||
| ORION Fission | 5.7 | 43,000 | 263,000 | 200 | no | ||
| THS HI Fusion Pulse | 6 | 300,000 | 40,000 | 4 | yes | ||
| THS HT Fusion Pulse | 6 | 150,000 | 80,000 | 4 | yes | ||
| ACMF | 6.6 | 132,300 | 100,000 | ? | no | ||
| ORION Fusion | 10.7 | 73,000 | 292,000 | 200 | no | ||
| NTR-SOLID/DUMBO | 14.0- 4.6 | see above | 3,500,000 | 5 | yes | ||
| Space Shuttle x3 SSME | 15.2 | 4,400 | 6,834,000 | yes | |||
| Single Saturn-V F-1 | 23 | 2,982 | 7,740,500 | yes | |||
| H-B Fusion | 30 | 980,000 | 61,000 | 300 | no | ||
| AM-Plasma/Water | 30 | 980,000 | 61,000 | 500 | no | ||
| Space Shuttle x2 SRB | 32 | 2,600 | 26,000,000 | yes | |||
| NTR-SOLID MAX | 42 | 12,000 | 7,000,000 | 15 | yes | ||
| NTR-LIQUID max | 56 | 16,000 | 7,000,000 | 70 | yes | ||
| NTR-GAS/Open (H2) | 61 | 35,000 | 3,500,000 | 30-200 | yes | ||
| Mini-Mag Orion | 66 | 210,000 | 625,000 | ? | yes? | ||
| NTR-GAS/Open 2nd Gen | 100 | 50,000 | 5,000,000 | 30-200 | yes | ||
| AV:T Fusion 3rd Gen Cruise Mode | 102 | 832,928 | 245,250 | ? | no | ||
| Saturn-V first stage x5 F-1 | 115 | 3,000 | 38,702,500 | yes | |||
| NTR-GAS MAX | 150 | 98,000 | 3,000,000 | 15 | yes | ||
| NTR-GAS/Coaxial (H2) | 157 | 17,658 | 17,800,000 | 127 | yes | ||
| He3-D Fusion | 192 | 7,840,000 | 49,000 | 1200 | no | ||
| AM-Plasma/Hydrogen | 192 | 7,840,000 | 49,000 | 500 | no | ||
| MC-Fusion MAX | 200 | 8,000,000 | 50,000 | 0.6 | yes | ||
| NSWR 20% enriched UTB | 427 | 66,000 | 12,900,000 | 33 | yes | ||
| IBS Agamemnon | 1,095 | 219,000 | 10,000,000 | ? | no | ||
| 1959 ORION 1st Gen | 1,600 | 39,000 | 80,000,000 | 1,700 | yes | ||
| AV:T Fusion 3rd Gen Combat Mode | 2,540 | 104,116 | 48,828,125 | ? | yes | ||
| 1959 ORION 2nd Gen | 24,000 | 120,000 | 400,000,000 | 3,250 | yes | ||
| NSWR 90% enriched UTB MAX | 31,000 | 4,700,000 | 13,000,000 | ? | yes | ||
| ORION MAX | 39,000 | 9,800,000 | 8,000,000 | 8 | yes | ||
| IC-Fusion MAX | 500,000 | 10,000,000 | 100,000,000 | 1000 | yes | ||
| H->He Fusion MAX | ? | 30,000,000 | ? | ? | yes | ||
| H->Fe Fusion MAX | ? | 50,000,000 | ? | ? | yes | ||
| AM-Beam MAX | 500,000 | 100,000,000 | 10,000,000 | 10 | ? | ||
| Photon | ? | 299,792,458 | ? | ? | ? |
Aluminum-Oxygen chemical rocket
Image courtesy of NASA
Methane-Oxygen chemical rocket
Methane and oxygen are burned resulting in an unremarkable specific impulse of about 377 seconds. However, this is the highest performance of any chemical rocket using fuels that can be stored indefinitely in space. Chemical rockets with superior specific impulse generally use liquid hydrogen, which will eventually leak away by escaping between the the molecules composing your fuel tanks. Liquid methane and liquid oxygen will stay put.
Hydrogen-Oxygen chemical rocket
Hydrogen and oxygen are burned resulting in close to the theoretical maximum specific impulse of about 450 seconds. However, liquid hydrogen cannot be stored permanently in any tank composed of matter. The blasted stuff will escape atom by atom between the molecules composing the fuel tanks.
Antiproton-catalyzed Microfission/Inertial Confinement Fission
See here.
Antiproton-initiated Microfusion/Inertial Confinement Fusion
See here.
Antimatter Beam Core
Image courtesy of NASA
Antimatter Gas Core
Microscopic amounts of antimatter are injected into large amounts of water or hydrogen propellant. The intense reaction flashes the propellant into plasma, which exits through the exhaust nozzle. Magnetic fields constrain the charged pions from the reaction so they heat the propellant, but uncharged pions escape and do not contribute any heating. Less efficient than AM-Solid core, but can achieve a higher specific impulse. For complicated reasons, a spacecraft optimized to use an antimatter propulsion system need never to have a mass ratio greater than 4.9, and may be as low as 2. No matter what the required delta V, the spacecraft requires a maximum of 3.9 tons of reaction mass per ton of dry mass, and a variable amount of antimatter measured in micrograms to grams.
Well, actually this is not true if the delta V required approaches the speed of light, but it works for normal interplanetary delta Vs.
Well, actually this is not true if the delta V required approaches the speed of light, but it works for normal interplanetary delta Vs.
Antimatter Plasma Core
Similar to antimatter gas core, but more antimatter is used, raising the propellant temperature to levels that convert it into plasma. A magnetic bottle is required to contain the plasma.
Antimatter Solid Core
Basically a NERVA design where a tungsten target replaces the reactor. 13 micrograms per second of antiprotons are annihilated. The gamma rays and pions are captured in the tungsten target, heating it. The tungsten target in turn heats the hydrogen. Produces high thrust but the specific impulse is limited due to material constraints (translation: above a certain power level the blasted tungsten melts)
ArcJet
AV:T Fusion
Radiators extended to signal surrender.
In the right illustration, the spikes are solid-state graphite heat radiators, the cage the spikes emerge from is the magnetic bottle, the sphere is the crew quarters and the yellow rectangles are the retractable power reactor heat radiators. The ship in the lower left corner is signaling its surrender by deploying its radiators.
Beer
Artwork by Ed Emshwiller
Chemical
Colloid Electrostatic
Deuterium-Tritium Fusion
Note that Tritium has an exceedingly short half-life of 12.32 years. Use it or lose it. Most designs using Tritium included a blanket of Lithium to breed more fresh Tritium fuel.
Hydrogen-Boron Fusion
Diagram from Alex H.Y. Cheung
Well, sort of. Current research indicatates that there may be some neutrons. Paul Dietz says there are two nasty side reactions. One makes a Carbon-12 atom and a gamma ray, the other makes a Nitrogen-14 atom and a neutron. The first side reaction is quite a bit less likely than the desired reaction, but gamma rays are harmful and quite penetrating. The second side reaction occurs with secondary alpha particles before they are thermalized.
The Hydrogen - Boron reaction is sometimes termed "thermonuclear fission" as opposed to the more common "thermonuclear fusion".
A pity about the low thrust. The fusion drives in Larry Niven's "Known Space" novels probably have performance similar to H-B Fusion, but with millions of newtons of thrust.
It sounded too good to be true, so I asked "What's the catch?"
The catch is, you have to arrange for the protons to impact with 300 keV of energy, and even then the reaction cross section is fairly small. Shoot a 300 keV proton beam through a cloud of boron plasma, and most of the protons will just shoot right through. 300 keV proton beam against solid boron, and most will be stopped by successive collisions without reacting. Either way, you won't likely get enough energy from the few which fuse to pay for accelerating all the ones which didn't.
Now, a dense p-B plasma at a temperature of 300 keV is another matter. With everything bouncing around at about the right energy, sooner or later everything will fuse. But containing such a dense, hot plasma for any reasonable length of time, is well beyond the current state of the art. We're still working on 25 keV plasmas for D-T fusion.
If you could make it work with reasonable efficiency, you'd get on the order of ten gigawatt-hours of usable power per kilogram of fuel.
Now, a dense p-B plasma at a temperature of 300 keV is another matter. With everything bouncing around at about the right energy, sooner or later everything will fuse. But containing such a dense, hot plasma for any reasonable length of time, is well beyond the current state of the art. We're still working on 25 keV plasmas for D-T fusion.
If you could make it work with reasonable efficiency, you'd get on the order of ten gigawatt-hours of usable power per kilogram of fuel.
Helium3-Deuterium Fusion
Fuel is helium3 and deuterium. Propellant is hydrogen. 1 atom of Deuterium fuses with 1 atom of Helium-3 to produce 18.35 MeV of energy. One gigawatt of power requires burning a mere 0.00285 grams of 3He-D fuel per second.
Tandem mirror engine.
"Field Reversed Configuration"
Discovery II from NASA report.
Discovery II
Discovery II
Discovery II magnetic nozzle.
Discovery II magnetic nozzle details.
IBS Agamemnon
Inertial Confinement Fusion
Ion
NASA NSTAR for Deep Space 1
If you are interested in the technical details about why ion drives are low thrust, read on.
And it suffers from the same critical thrust-limiting problem as any other ion engine: since you are accelerating ions, the acceleration region is chock full of ions. Which means that it has a net space charge which repels any additional ions trying to get in until the ones already under acceleration manage to get out, thus choking the propellant flow through the thruster.
The upper limit on thrust is proportional to the cross-sectional area of the acceleration region and the square of the voltage gradient across the acceleration region, and even the most optimistic plausible values (i.e. voltage gradients just shy of causing vacuum arcs across the grids) do not allow for anything remotely resembling high thrust.
The upper limit on thrust is proportional to the cross-sectional area of the acceleration region and the square of the voltage gradient across the acceleration region, and even the most optimistic plausible values (i.e. voltage gradients just shy of causing vacuum arcs across the grids) do not allow for anything remotely resembling high thrust.
You can only increase particle energy so much; you then start to get vacuum arcing across the acceleration chamber due to the enormous potential difference involved. So you can't keep pumping up the voltage indefinitely.
To get higher thrust, you need to throw more particles into the mix. The more you do this, the more it will reduce the energy delivered to each particle.
It is a physical limit. Ion drives cannot have high thrusts.
To get higher thrust, you need to throw more particles into the mix. The more you do this, the more it will reduce the energy delivered to each particle.
It is a physical limit. Ion drives cannot have high thrusts.
J x B Electric
"Jay cross Bee". A crossed field plasma accelerator. It is a type of Magnetoplasmadynamic propulsion.
LANTR
Laser Thermal
Mass Driver
Mass drivers: buckets filled with packed rock dust are accelerated electromagnetically. Buckets are recovered for re-use. Propellant is rock dust or anything else you can stuff into the bucket. Popular with asteroid miners who want to nudge their claims into different orbits. However, their existence may prompt the creation of an Orbital Guard.
Magnetic Confinement Fusion
A magnetic bottle contains the fusion reaction. Very difficult to do. Researchers in this field say that containing fusion plasma in a magnetic bottle is like trying to support a large slab of gelatin with a web of rubber bands. Making a magnetic bottle which has a magnetic rocket exhaust nozzle is roughly 100 times more difficult.
Meta-helium He*
Spin-polarized triplet helium. Three helium atoms are aligned in a metastable state. When it reverts to normal state it releases 0.48 gigjoules per kilogram. The trouble is that it tends to decay spontaneously, with a lifetime of a mere 2.3 hours.
Meta-helium He IV-A
Diatomic metastable helium. One normal and one excited helium atom are paired to form a stable solid.
The trick is to keep the touchy stuff from exploding prematurely and destroying the spacecraft. The fuel is stored in a resonant waveguide. This is another propulsion system that renders the spacecraft unusually vulnerable to weapons strikes.
The trick is to keep the touchy stuff from exploding prematurely and destroying the spacecraft. The fuel is stored in a resonant waveguide. This is another propulsion system that renders the spacecraft unusually vulnerable to weapons strikes.
Mini-MagOrion
MITEE
Basic MITEE
The baseline design is a fairly conventional NTR. Unlike earlier designs it keeps the fuel elements in individual pressure tubes instead of a single pressure vessel, making it lighter and allowing slightly higher temperatures and a bit better exhaust velocity.
Monatomic H MITEE
This advanced design works at a lower chamber pressure so that some of the H2 propellant disassociates into monatomic hydrogen, although the chamber temperature is only slightly greater. The drawback is that this reduces the mass flow through the reactor, limiting reactor power.
Hybrid Electro-Thermal MITEE
The use of individual pressure tubes in the reactor allows some fuel channels to be run at high pressure while others are run at a lower pressure, facilitating a hybrid electro-thermal design. In this design cold H2 is heated in the high pressure section of the reactor, is expanded through a turbine connected to a generator, then reheated in the low pressure section of the reactor before flowing to the nozzle. The electricity generated by the turbine is used to break down more H2 into monatomic hydrogen, increasing the exhaust velocity. Since this is a once through system there is no need for radiators so the weight penalty would not be excessive.
Magnetoplasmadynamic
A travelling wave plasma accelerator. Propellant is potassium seeded helium.
Nuclear Salt-water Rocket
From AIAA 90-2371 Nuclear Salt Water Rockets: High Thrust at 10,000 sec Isp
It is basically a continuously detonating Orion type drive with water as propellant. Although Zubrin puts it like this:
As the solution continues to pour into the plenum from the borated storage pipes, a steady-state conditions of a moving detonating fluid can be set up within the plenum.
The controversy is over how to contain such a nuclear explosion. Zubrin maintains that skillful injection of the fuel can force the reaction to occur outside the reaction chamber. He says that the neutron flux is concentrates on the downstream end due to neutron convection. Other scientists are skeptical.
Naturally in such a spacecraft, damage to the fuel tanks can have unfortunate results (say, damage caused by hostile weapons fire). Breach the fuel tubes and you'll have a runaway nuclear chain reaction on your hands. Inside your ship.
The advantage of NSWR is that this is the only known propulsion system that combines high exhaust velocity with high thrust. The disadvantage is that it combines many of the worst problems of the Orion and Gas Core systems. For starters, using it for take-offs will leave a large crater that will glow blue for several hundred million years, as will everything downwind in the fallout area.
Zubrin calculates that the 20% enriched uranium tetrabromide will produce a specific impulse of about 7000 seconds (69,000 m/s exhaust velocity), which is comparable to an ion drive. However, the NSWR is not thrust limited like the ion drive. Since the NSWR vents most of the waste heat out the exhaust nozzle, it can theoretically produce jet power ratings in the thousands of megawatts. Also unlike the ion drive, the engine is relatively lightweight, with no massive power plant required.
Zubrin suggests that a layer of pure water be injected into the plenum to form a moving neutron reflector and to protect the plenum walls and exhaust nozzle from the heat. One wonders how much protection this will offer.
Zubrin gives a sample NSWR configuration. It uses as fuel/propellant a 2% (by number) uranium bromide aqueous solution. The uranium is enriched to 20% U235. This implies that B2 = 0.6136 cm-2 (the material buckling, equal to vΣf-Σa)/D) and D = 0.2433 cm (diffusion coefficent).
Radius of the reaction plenum is set to 3.075 centimeters. this implies that A2 = 0.6117 cm-2 and L2 = 0.0019. Since exponential detonation is desired, k2 = 2L2 = 0.0038 cm-2. Then k = U / 2D = 0.026 cm-1 and U = 0.03.
If the velocity of a thermal neutron is 2200 m/s, this implies that the fluid velocity needs to be 66 m/s. This is only about 4.7% the sound speed of room temperature water so it should be easy to spray the fuel into the plenum chamber at this velocity.
The total rate of mass flow through the plenum chamber is about 196 kg/s.
Complete fission of the U235 would yield about 3.4 x 1012 J/kg. Zubrin assumes a yield of 0.1% (0.2% at the center of the propellant column down to zero at the edge), which would not affect the material buckling during the burn. This gives an energy content of 3.4 x 109 J/kg.
Assume a nozzle efficiency of 0.8, and the result is an exhaust velocity of 66,000 m/s or a specific impules of 6,7300 seconds. The total jet power is 427 gigawatts. The thrust is 12.9 meganewtons. The thrust-to-weight ratio will be about 40, which implies an engine mass of about 33 metric tons.
For exponetial detonation, kz has to be about 4 at the plenum exit. Since k = 0.062 cm-1, the plenum will have to be 65 cm long. The plenum will be 65 cm long with a 3.075 cm radius, plus an exhaust nozzle.
Zubrin then goes on to speculate about a more advanced version of the NSWR, suitable for insterstellar travel. Say that the 2% uranium bromide solution used uranium enriched to 90% U235 instead of only 20%. Assume that the fission yield was 90% instead of 0.1%. And assume a nozzle efficency of 0.9 instead of 0.8.
That would result in an exhaust velocity of a whopping 4,725,000 m/s (about 1.575% c, a specific impulse of 482,140 seconds). In a ship with a mass ratio of 10, it would have a delta V of 3.63% c. Now you're talkin...
Gaseous Core Nuclear Thermal Rocket
NTR-GAS/Closed
Image from NASA Report, Studies of Specific Nuclear Light Bulb and Open-Cycle Vortex-Stabilized Gaseous Nuclear Rocket Engines. Warning: I did the color-coding myself, I may have gotten some of the details incorrect.
You can read more about this on the Unwanted Blog in the posts here,here, and here.
The good news is that unlike the open-cycle GCNR it does not spray glowing radioactive death there is no uranium escaping in the exhaust. The bad news is that the maximum exhaust velocity is halved, as is the Delta-V. Yes, I did ask some experts if it was possible to make some kind of hybrid that could "shift gears" between closed and open cycle. Sorry, there would be no savings over just having two separate engines.
The maximum exhaust velocity is halved because you are trying to have it both ways at once. The higher the propellant's temperature, the higher the exhaust velocity and rocket Delta-V. Unfortunately solid core nuclear reactors have a distressing habit of vaporizing at high temperatures (as do all material objects). Gas core reactors are attempting to do an end run around this problem, by having the reactor start out as high temperature vapor. But adding the quartz chamber is re-introducing solid material components into the engine, which kind of defeats the purpose. The only thing keeping this from utter failure is the fact that quartz does not heat up as much due to the fact it is transparent.
Even with the restrictions, it seems possible to make a closed-cycle GCNR with a thrust to weight ratio higher than one. This would allow using the awesome might of the atom to boost truely massive amounts of payload into Terra orbit, without creating a radioactive wasteland with every launch. See the GCNR Liberty Ship for an example. The Liberty Ship can boost in one launch more payload than any given Space Shuttle does in the shuttles entire 10 year operating life. Then the Liberty Ship can land and do it again.
The ideal solution would be to somehow constrain the uranium by something non-material, such as a mangnetohydrodynamic force field or something like that. Alas, currently such fields can only withstand pressures on the order of the breeze from a flapping mosquito, not the 500 atmospheres of pressure found here. But since researchers are working along the same lines in their attempts to make a fusion reactor, this may change. And I did find a brief reference to something called an "MHD choke" in reference to slowing the escape of uranium into the exhaust stream of an open-cycle gas core rocket. I'm still trying to find more information on that.
NASA Report Summary
The pictured engine is the "reference engine" described in the report Studies of Specific Nuclear Light Bulb and Open-Cycle Vortex-Stabilized Gaseous Nuclear Rocket Engines (PDF file). I will give the high-lights from the report, but for all the boring nitty-gritty details you'll have to read the report yourself. Please note that as always, "down" is the direction the thrust is going (to the right in the blueprint) and "up" is the opposite direction (to the left). I apologize for the use of imperial units instead of metric. The report is in imperial, and it is too much of a pain to change everything.
The important statistics: Specific impulse is 1870 seconds (18,300 m/s), thrust 42,000 newtons, engine mass 32,000 kg, thrust-to-weight ratio 1.3.
The other stats. The total volume of the reaction chambers (cavities) is 170 cubic feet. There are seven cavities, each six feet long. The cavity pressure is 500 atmospheres. The specific impulse is 1870 seconds (report says can theoretically be from 1500 to 3000 seconds). The total propellant flow (including seed and nozzle transpirant coolant flow) is 49.3 pounds per second. The thrust is 92,000 pounds. The engine power is 4600 megawatts. The engine weight is 70,000 pounds. If one can design a variable-throat-area nozzle (instead of fixed-area) this will result in a major decrease in the required chamber pressure during startup.
The important statistics: Specific impulse is 1870 seconds (18,300 m/s), thrust 42,000 newtons, engine mass 32,000 kg, thrust-to-weight ratio 1.3.
The other stats. The total volume of the reaction chambers (cavities) is 170 cubic feet. There are seven cavities, each six feet long. The cavity pressure is 500 atmospheres. The specific impulse is 1870 seconds (report says can theoretically be from 1500 to 3000 seconds). The total propellant flow (including seed and nozzle transpirant coolant flow) is 49.3 pounds per second. The thrust is 92,000 pounds. The engine power is 4600 megawatts. The engine weight is 70,000 pounds. If one can design a variable-throat-area nozzle (instead of fixed-area) this will result in a major decrease in the required chamber pressure during startup.
Configuration
The basic configuration is seven separate unit cavities surrounded by moderator-reflector material in between each cavity (beryllium oxide) and surrounding the entire cavity array (graphite). Each cavity is 6.0 feet long and the total volume of all seven cavities is 169.8 cubic feet. The cavity pressure is 500 atmospheres due to criticality and fuel density considerations.
Lightbulbs
In each lightbulb, a critical mass of gaseous uranium creates thermal radiation. The thermal radiation can pass through the transparent quartz crystal walls of the lightbulb, but the uranium vapor cannot. This means no lethal uranium enters the exhaust. Hydrogen propellant flowing over the lightbulb is heated to high temperatures by the thermal radiation and is expelled out the rocket nozzles, producing thrust. The hydrogen is "seeded" with tungsten dust because it too is ordinarily transparent to thermal radiation. The seeding makes it opaque, and allows it to be heated. Seven "lightbulbs" are used instead of one, since that increases the total lightbulb radiating area by about 2.2 times.
Transparent quartz walls
The transparent quartz wall of the lightbulb contains lots of coolant channels. This is because the quartz is mostly transparent to thermal radiation, but not totally. And fissioning uranium produces an awful lot of thermal radiation. I told you that nuclear lightbulb designers were trying to have it both ways. The coolant channels are marked "circumferential coolant tubes" in the diagram below.
Inside a lightbulb
Inside the lightbulb, neon buffer gas is used to create a vortex ring to suspend the gaseous nuclear fuel (a "radial inflow" vortex). The vortex ring looks like an elongated donut (I know it looks like two separate blobs above, that's due to the fact the diagram is a cross-section). One of the important jobs done by the neon buffer gas is to prevent the 42,000°R uranium plasma from making contact with the lightbulb walls. This would be very bad, as the walls would be instantly vaporized. The neon passes along the lightbulb walls, bends round the end caps, then travels down the long axis of the lightbulb (right down the center of the vortex ring). When it reaches the fore end cap, it is removed from the lightbulb through a port (marked "thru-flow" in diagram above).
The removed neon is very hot, and contains unburnt uranium and fission products. It is cooled by mixing with low-temperature neon, which condenses the unburnt uranium vapor into hot liquid uranium. The liquid uranium is separated from the neon by a centrifuge and sent back into the vortex (at point marked "fuel injection"). The neon is cooled further then it too is sent back into the vortex (at point marked "buffer gas injection"). While examining the blueprint, I noticed that the centrifuges, and indeed the entire uranium fuel delivery system is conspicuous by its absence. Probably classified.
Note that the centrifuges is a neat solution to the problem of fission fragments clogging up the fuel. In essence, this design has its own built-in nuclear fuel reprocessing plant. Of course the nasty fission fragments will have to be stored and eventually disposed of.
The removed neon is very hot, and contains unburnt uranium and fission products. It is cooled by mixing with low-temperature neon, which condenses the unburnt uranium vapor into hot liquid uranium. The liquid uranium is separated from the neon by a centrifuge and sent back into the vortex (at point marked "fuel injection"). The neon is cooled further then it too is sent back into the vortex (at point marked "buffer gas injection"). While examining the blueprint, I noticed that the centrifuges, and indeed the entire uranium fuel delivery system is conspicuous by its absence. Probably classified.
Note that the centrifuges is a neat solution to the problem of fission fragments clogging up the fuel. In essence, this design has its own built-in nuclear fuel reprocessing plant. Of course the nasty fission fragments will have to be stored and eventually disposed of.
Lightbulb dimensions
The total volume inside all the lightbulbs is 84.9 cubic feet, which is 12.1 cubic feet per lightbulb. The radius of the uranium fuel containing region is 85% of the radius of the transparent wall. While the fissioning uranium fuel has a core temperature of 42,000° Rankine, the outer surface is only at 15,000° Rankine.
Propellant flow in a lightbulb
The propellant is assumed to exit with a temperature of 80% of the fuel temperature, or 12,000° Rankine. This is because the quartz transparent walls will reflect about 15% of the thermal radiation back inside. By some compilcated reasoning that you will find in the report, the total thermal radiation from the lightbulbs is 4.37 x 106 BTU/sec. The hydrogen propellant has an "enthalpy"of 1.033 x 105 BTU/pound at 12,000°R. So by dividing the two, one discovers that the entire engine can support a propellant flow rate of 42.3 pounds per second, which means 6.07 lb/sec for each of the seven cavities.
If that last paragraph confused you, let me explain. As a simple example, if a pound of hydrogen at 5°R contains 2 BTUs ("enthalpy"), and the engine puts out 6 BTU per second, then obviously the engine can heat up 6 / 2 = 3 pounds of hydrogen per second. Why do we care? If you multiply the propellant flow rate by the exhaust velocity you will discover the engine's thrust value. And that's a number we do care about.
If that last paragraph confused you, let me explain. As a simple example, if a pound of hydrogen at 5°R contains 2 BTUs ("enthalpy"), and the engine puts out 6 BTU per second, then obviously the engine can heat up 6 / 2 = 3 pounds of hydrogen per second. Why do we care? If you multiply the propellant flow rate by the exhaust velocity you will discover the engine's thrust value. And that's a number we do care about.
Colored diagram of a primary circuit inlet.
The tungsten dust that the propellant is seeded with has a particle diameter of 0.05 microns. The seed density is 1.32 x 10-2 lb/ft3, which is about 3.9 percent of the inlet propellant density. This can probably be reduced if tungsten dust was in the form of thin flat plates instead of spherical particles.
The hydrogen propellant enters the pressure shells from the fore end (see "Primary Circuit Inlet" in pressure shell diagram below). A bit is bled off from small H2 flow ports in order to pressurize the interior of the shells, circulating to provide coolant to the engines and machinery. But most of it is fed into the turbopump, then injected into the cavities. Since the fore end of each cavity is almost blocked off by the butt end of the lightbulb, there is only a narrow rim to inject the hydrogen.
In the diagram to the right, you can see how the propellant is fed from the pink pipe into the pink-and-gold wedge-shaped injectors. I presume there are three injectors per cavity, spraying into the clear area between the transparent wall's coolant manifolds and buffer gas injectors.
The hydrogen propellant enters the pressure shells from the fore end (see "Primary Circuit Inlet" in pressure shell diagram below). A bit is bled off from small H2 flow ports in order to pressurize the interior of the shells, circulating to provide coolant to the engines and machinery. But most of it is fed into the turbopump, then injected into the cavities. Since the fore end of each cavity is almost blocked off by the butt end of the lightbulb, there is only a narrow rim to inject the hydrogen.
In the diagram to the right, you can see how the propellant is fed from the pink pipe into the pink-and-gold wedge-shaped injectors. I presume there are three injectors per cavity, spraying into the clear area between the transparent wall's coolant manifolds and buffer gas injectors.
Uranium fuel
The total fissioning uranium in all seven vortexes be about 25.2 pounds of uranium (about 3.6 pounds per cavity). You would ordinarily need more to ensure nuclear criticality, but the required amount is brought down by the beryllium oxide neutron reflector encasing each cavity. The average uranium fuel density is 0.409 lb/ft3. The total density of the neon-uranium mix inside the vortex is about 0.56 lb/ft3. A unit of neon gas will spend about 3.8 seconds inside the cavity. A unit of uranium will spend about 19 seconds inside the cavity. This implies a uranium fuel flow rate of 0.19 lb/sec per cavity.
According to my slide rule, if the array of seven cavities is producing 4,600 megawatts, it means that the array is burning a miniscule total of 0.055 grams (0.00012 pounds) of uranium fuel per second (0.0079 grams per cavity per second). It still needs the full 3.6 pounds per cavity to be present in order to burn the fraction of a gram.
The theoretical maximum specific impulse possible is 2230 seconds. Due to this designs incomplete expansion, transpiration coolant flow in the nozzle, presence of tungsten seeding, and friction losses the specific impulse is reduced to 84% or 1870 seconds. Total propellant flow (allowing for tungsten seeds and transpiration cooling) is 49.3 lb/sec. This would result in a thrust of 92,000 pounds force. For complicated reasons you can find in the report, this implies that the exhaust nozzles are 0.0875 feet in diameter at the throat expanding to 2.04 feet diameter at the exit.
According to my slide rule, if the array of seven cavities is producing 4,600 megawatts, it means that the array is burning a miniscule total of 0.055 grams (0.00012 pounds) of uranium fuel per second (0.0079 grams per cavity per second). It still needs the full 3.6 pounds per cavity to be present in order to burn the fraction of a gram.
The theoretical maximum specific impulse possible is 2230 seconds. Due to this designs incomplete expansion, transpiration coolant flow in the nozzle, presence of tungsten seeding, and friction losses the specific impulse is reduced to 84% or 1870 seconds. Total propellant flow (allowing for tungsten seeds and transpiration cooling) is 49.3 lb/sec. This would result in a thrust of 92,000 pounds force. For complicated reasons you can find in the report, this implies that the exhaust nozzles are 0.0875 feet in diameter at the throat expanding to 2.04 feet diameter at the exit.
Uranium refueling
Careful readers may have noticed how the description avoids mentioning the details on how one gets the uranium into the lightbulbs. This is because it is quite a difficult problem, and each of the proposed solutions has drawbacks. The basic problem is old reliable: all the atomic fireworks inherent in 235U will happen if you merely let too much of it accumulate in one place. You have to store it diffuse and somehow bring it together in the lightbulb.
Method #1 Store it as uranium hexafluoride gas. This would be in large tanks of low pressure (i.e., low density) and with the tanks full of neutron absorbing foam. Pump enough into the lightbulb, a chain reaction will start, and well before the reaction reaches 13,000°R the uranium will have separated from the fluorine.
The problem is that now you have the insanely dangerous task of dealing with 13,000°R florine gas. At room temperature the blasted stuff will violently react with any element in the known universe except helium and neon. A temperature of 13,000°R makes it about 13,000 times as deadly. It will explosively corrode away anything solid in its path like molten lead on facial tissue. Chemist Derek Lowe sarcastically notes that "At seven hundred freaking degrees, fluorine starts to dissociate into monoatomic radicals, thereby losing its gentle and forgiving nature." You can read more about the suicidal risk of dealing with hot fluorine in his amusing blog post.
Method #2 Store it as sub-critical chunks of uranium, melt them, and inject the molten uranium into the lightbulb. Uranium melts at 1403°K, which is difficult but not impossible. The plan is to somehow turn the molten uranium into a sort of aerosol mist suspended in hot neon.
The problem is that the molten uranium wants to plate itself all over the melter and the aerosol spray equipment. Which is annoying if the material in question is something like lead, but disasterous if the material is radioactive and fissionable.
Method #3 is to store the uranium cold as finely divided dust. As dust it is pumpable, injectable, and it will not plate over everything. Inside the lightbulb the uranium dust will be rapidly heated to vaporization by the nuclear reaction. This method does not have any major problems, except for the common problem of how to protect the transparent wall from being vaporized by the heat.
Again, the uranium delivery system seems to be totally missing from the blueprint. The only bit present is the short stub of the injector at the top of each lightbulb.
Method #1 Store it as uranium hexafluoride gas. This would be in large tanks of low pressure (i.e., low density) and with the tanks full of neutron absorbing foam. Pump enough into the lightbulb, a chain reaction will start, and well before the reaction reaches 13,000°R the uranium will have separated from the fluorine.
The problem is that now you have the insanely dangerous task of dealing with 13,000°R florine gas. At room temperature the blasted stuff will violently react with any element in the known universe except helium and neon. A temperature of 13,000°R makes it about 13,000 times as deadly. It will explosively corrode away anything solid in its path like molten lead on facial tissue. Chemist Derek Lowe sarcastically notes that "At seven hundred freaking degrees, fluorine starts to dissociate into monoatomic radicals, thereby losing its gentle and forgiving nature." You can read more about the suicidal risk of dealing with hot fluorine in his amusing blog post.
Method #2 Store it as sub-critical chunks of uranium, melt them, and inject the molten uranium into the lightbulb. Uranium melts at 1403°K, which is difficult but not impossible. The plan is to somehow turn the molten uranium into a sort of aerosol mist suspended in hot neon.
The problem is that the molten uranium wants to plate itself all over the melter and the aerosol spray equipment. Which is annoying if the material in question is something like lead, but disasterous if the material is radioactive and fissionable.
Method #3 is to store the uranium cold as finely divided dust. As dust it is pumpable, injectable, and it will not plate over everything. Inside the lightbulb the uranium dust will be rapidly heated to vaporization by the nuclear reaction. This method does not have any major problems, except for the common problem of how to protect the transparent wall from being vaporized by the heat.
Again, the uranium delivery system seems to be totally missing from the blueprint. The only bit present is the short stub of the injector at the top of each lightbulb.
Pressure shells
The entire engine is encased in two nested pressure shells constructed of filament-wound fiberglass. The inside of the inner shell is pressurized to 500 atmospheres. Hydrogen propellant enters through a 0.5 foot diameter duct at the fore end (aka "Primary Circuit Inlet"). There are seven 0.4 foot diameter holes in the aft end for the engine nozzles, one at zero degrees off-axis, the other six at 60°. The pressure shell can be separated into two parts along the flange at the point of maximum diameter, to allow an engineer or waldo manipulator access to the engine interior. This point is also where the rear structural grid protrudes from the interior, this is where the engine bolts onto the structural frame of the spacecraft to transmit the engine thrust.
If you look at the large blueprint, you will see that parts of the rear structural grid penetrate the cavities to support the end-caps of the quartz lightbulbs.
If you look at the large blueprint, you will see that parts of the rear structural grid penetrate the cavities to support the end-caps of the quartz lightbulbs.
Coolant system
The plumbing for the coolant system is rather complicated(translation: I don't understand it all). Click for larger image. You can use this diagram along with the large blueprint to attempt to puzzle out what all the pipes are for. Basically the propellant enters the system through the "Primary circuit inlet" (at lower left of plumbing diagram, and in the pressure shell diagram above)and leaves the system via the "Propellant injection" arrow, where the propellant is heated by the lightbulbs in the cavity and jets out the exhaust nozzles. In between, the propellant frantically threads its way over every single other engine component in a desperate attempt to cool them off.
Propellant flow overview
In the blueprints you can see how the pipes that feed the propellant injectors are originally fed from horns over the graphite moderators. Which is exactly as per the plumbing diagram.
Propellant flow through a primary circuit inlet.- Colored diagram of a primary circuit inlet.
This is my best guess at how the hydrogen propellant flows through the engine. It may be incorrect, use at your own risk. It starts with the green arrow at the left. This is the Primary circuit inlet at the nose of the engine, where the propellant enters the pressure shell. The pipe splits several ways (probably six ways, one for each outer cavity) and enters the base of the turbopump (arrows change color to Yellow).
Pipe runs to the inner shell, then I hypothesize that there is a connection between the two bumps on the inner shell. Propellant runs to the inner pipe array just on top of the cavities, then it is injected into coolant channels in the beryllium oxide moderator around the tie rods. After cooling the beryllium, it spurts out and enters the base of the graphite moderator surrounding the hexagonal beryllium array (arrows change color to orange). It passes through coolant channels in the graphite, and emerges at the top into the collector horns. There it enters the outer pipe array above the inner pipe array.
This feeds the three wedge shaped propellant injectors on each cavity. This injects the propellant around the edge of the transparent light bulbs (arrows change color to red). The propellant shoots aft while being heated by the thermal radiation from the light bulbs. The hot propellant then jets out the exhuast nozzles and thrust occurs.
Pipe runs to the inner shell, then I hypothesize that there is a connection between the two bumps on the inner shell. Propellant runs to the inner pipe array just on top of the cavities, then it is injected into coolant channels in the beryllium oxide moderator around the tie rods. After cooling the beryllium, it spurts out and enters the base of the graphite moderator surrounding the hexagonal beryllium array (arrows change color to orange). It passes through coolant channels in the graphite, and emerges at the top into the collector horns. There it enters the outer pipe array above the inner pipe array.
This feeds the three wedge shaped propellant injectors on each cavity. This injects the propellant around the edge of the transparent light bulbs (arrows change color to red). The propellant shoots aft while being heated by the thermal radiation from the light bulbs. The hot propellant then jets out the exhuast nozzles and thrust occurs.
Cross sections
Here are a set of cross sections through the cavities. The one on the left is zoomed in on the cavity interior, the other two gradually zoom out.
NTR-GAS/Coaxial
Circa 1960 NASA-Lewis concept for a gas core nuclear rocket engine. Specific Impulse 2200 seconds (exhaust velocity 22,000 m/s). Thrust 45,000 newtons. Thrust to weight ratio 0.68 (engine mass 66,000 kilograms), reactor diameter 5 meters, overall reactor length 5 meters. The fuel would reach 20,000 degrees R, while the propellant would get to 10,000 degrees R. From The Unwanted Blog.
NTR-GAS/Open
From NASA Report, Mars Exploration Studies 1988 Volume 2
Nexus gas core heavy lift vehicle (1964). Isp of 2220 seconds, payload delivery of one million pounds to lunar orbit. From The Unwanted Blog
Nexus with chemical first stage, and gas core second stage. From The Unwanted Blog
CGI 3D rendering of the Nexus engines created by William Black
CGI 3D rendering of the Nexus engines created by William Black
Gaseous uranium is injected into the reaction chamber until there is enough to start a furious chain reaction. Hydrogen is then injected from the chamber walls into the center of this nuclear inferno where is flash heats and shoots out the exhaust nozzle.
The trouble is the uranium shoots out the exhaust as well.
The reaction is maintained in a vortex tailored to minimize loss of uranium out the nozzle. Fuel is uranium hexaflouride (U235F6), propellant is hydrogen. However, in one of the designs, U235is injected by gradually inserting into the fireball a long rod of solid uranium. The loss of uranium in the exhaust reduces efficiency and angers environmentalists.
In some designs the reaction chamber is spun like a centrifuge. This encourages the heavier uranium to stay in the chamber instead of leaking into the exhaust. This makes for a rather spectacular failure mode if the centrifuge's bearings seize.
You can find more details here.
If used for lift off it can result in a dramatic decrease in the property values around the spaceport, if not the entire county. An exhaust plume containing radioactive uranium is harmless in space but catastrophic in Earth's atmosphere.
Amusingly enough, this is the best match for the propulsion system used in the TOM CORBETT: SPACE CADET books. However the books are sufficiently vague that it is possible the Polaris used a nuclear lightbulb. According to technical advisor Willy Ley, "reactant" is the hydrogen propellant, but the books imply that reactant is the liquid uranium.
Liquid Core Nuclear Thermal Rocket
NTR-LIQUID/LARS
Nuclear thermal rocket / liquid annular reactor system. A type of NTR-LIQUID. You can find more details here
Solid Core Nuclear Thermal Rocket
"The enlisted men get to go out and shovel whatever they can find into the propellant tanks"
NERVA testing. From nuclearspace.com.
Hydrogen gives the best exhaust velocity, but the other propellants are given in the table since a spacecraft may be forced to re-fuel on whatever working fluids are available locally (what Jerry Pournelle calls "Wilderness re-fuelling", Robert Zubrin calls "In-situ Resource Utilization", and I call "the enlisted men get to go out and shovel whatever they can find into the propellant tanks"). For thermal drives in general, and NTR-SOLID in particular, the exhaust velocity imparted to a particular propellant by a given temperature is proportional to 1 / sqrt( molar mass of propellant chemical ).
The value for "hydrogen" in the table is for molecular hydrogen, i.e., H2. Atomic hydrogen would be even better, but unfortunately it tends to explode at the clank of a falling dust speck (Heinlein calls atomic hydrogen "Single-H"). Another reason to avoid hydrogen is the difficulty of storing the blasted stuff, and its annoyingly low density (Ammonia is abouteight times as dense!). Exhaust velocities are listed for a realistically attainable core temperature of 3200 degrees K for the propellants Hydrogen (H2), Methane (CH4), Ammonia (NH3), Water (H2O), Carbon Dioxide (CO2), Carbon Monoxide (CO), and Nitrogen (N2).
The exhaust velocities are larger than what one would expect given the molecular weight of the propellants because in the intense heat they break down into their components. Ammonia is nice because it breaks down into gases (Hydrogen and Nitrogen). Methane is nasty because it breaks down into Hydrogen and Carbon, the latter tends to clog the reactor with soot deposits. Water is most unhelpful since it doesn't break down much at all.
Dr. John Schilling figures that as an order of magnitude guess, about one day of full power operation would result in enough fuel burnup to require reprocessing of the fissionable fuel elements. (meaning that while there is still plenty of fissionables in the fuel rod, enough by-products have accumulated that the clogged rod produces less and less energy) A reprocessing plant could recover 55-95% of the fuel. With reprocessing, in the long term each totally consumed kilogram of plutonium or highly enriched uranium (HEU) will yield ~1E10 newton-seconds of impulse at a specific impulse of ~1000 seconds.
Dr. Schilling also warns that there is a minimum amount of fissionable material for a viable reactor. Figure a minimum of 50 kilograms of HEU.
One problem with solid-core NTRs is that if the propellant is corrosive, that is, if it is oxidizing orreducing, heating it up to three thousand degrees is just going to make it more reactive. Without a protective coating, the propellant will start corroding away the interior of the reactor, which will make for some real excitement when it starts dissolving the radioactive fuel rods. What's worse, a protective coating against an oxidizing chemical is worthless against a reducing chemical, which will put a crimp in your wilderness refueling. And trying to protect against both is an engineering nightmare. Oxidizing propellants include oxygen, water, and carbon dioxide, while reducing propellants include hydrogen, ammonia, and methane. Carbon Monoxide is neither, as the carbon atom has a death-grip on the oxygen atom.
Keep in mind that the oxidizing/reducing effect is only a problem with solid-core NTRs, not the other kinds. This is because only the solid-core NTRs have solid reactor elements exposed to the propellant (for heating).
A useful refinement is the Bimodal NTR.
Say your spacecraft has an honest-to-Johnny NERVA nuclear-thermal propulsion system. Typically it operates for a few minutes at a time, then sits idle for the rest of the entire mission. Before each use, one has to warm up the reactor, and after use the reactor has to be cooled down. Each of these thermal cycles puts stress on the engine. And the cooling process consists of wasting propellant, flushing it through the reactor just to cool it off instead of producing thrust.
Meanwhile, during the rest of the mission, your spacecraft needs electricity to run life support, radio, radar, computers, and other incidental things.
So make that reactor do double duty (that's where the "Bimodal" comes in) and kill two birds with one stone. Refer to above diagram. Basically you take a NERVA and attach a power generation unit to the side. The NERVA section is the "cryogenic H2 propellant tank", the turbopump, and the thermal propulsion unit. The power generation section is the generator, the radiator, the heat exchanger, and the compressor.
Warm up your reactor once, do a thrust burn, stop the propellant flow and use the heat exchanger and radiator to partially cool the reactor to power generation levels, and keep the reactor warm for the rest of the mission while generating electricity for the ship.
This allows you to get away with only one full warm/cool thermal cycle in the entire mission instead of one per burn. No propellant is wasted as coolant since the radiator cools down the reactor. The reactor supplies needed electricity. And as an added bonus, the reactor is in a constant pre-heated state. This means that in case of emergency one can power up and do a burn in a fraction of the time required by a cold reactor.
Pretty ingenious, eh?
TRITON Trimodal
TRITON Trimodal schematic
TRITON Trimodal and Brayton radiator
NTR-SOLID/DUMBO
This was a competing design to NERVA. It was shelved political decision that, (in order to cut costs on the atomic rocket projects) requiredboth projects to use an already designed NEVRA engine nozzle. Unfortunately, said nozzle was not compatible with the DUMBO active cooling needs. Dumbo does, however, have a far superior mass flow to the NERVA, and thus a far superior thrust. Dumbo actually had a thrust to weight ratio greater than one. NASA still shelved DUMBO because [a] NERVA used off the shelf components and [b] they knew there was no way in heck that they could get permission for nuclear lift-off rocket so who cares if T/W < 0? You can read more about Dumbo in this document.
NTR-SOLID/NERVA
Nuclear Engine for Rocket Vehicle Applications. The first type of NTR-SOLID propulsion systems. It used reactor fuel rods surrounded by a neutron reflector. Unfortunately its thrust to weight ratio is less than one, so no lift-offs with this rocket. The trouble was inadequate propellant mass flow, the result of trying to squeeze too much hydrogen through too few channels in the reactor.
NTR-SOLID/PBed
Particle bed / nuclear thermal rocket AKA fluidized-bed, dust-bed, or rotating-bed reactor. In the particle-bed reactor, the nuclear fuel is in the form of a particulate bed through which the working fluid is pumped. This permits operation at a higher temperature than the solid-core reactor by reducing the fuel strength requirements . The core of the reactor is rotated (approximately 3000 rpm) about its longitudinal axis such that the fuel bed is centrifuged against the inner surface of a cylindrical wall through which hydrogen gas is injected. This rotating bed reactor has the advantage that the radioactive particle core can be dumped at the end of an operational cycle and recharged prior to a subsequent burn, thus eliminating the need for decay heat removal, minimizing shielding requirements, and simplifying maintenance and refurbishment operations.
Orion
If you want the real inside details of the original Orion design, run, do not walk, and get a copy of Aerospace Projects Review issue Volume 2, Number 2. It has blueprints, tables, and lots of never before seen details. If you want your data raw, piled high and dry, here (PDF file) is a copy of report GA-5009 vol III "Nuclear Pulse Space Vehicle Study - Conceptual Vehicle Design" by General Atomics (1964). Lots of charts, lots of graphs, some diagrams.
The sad little secret about Orion is that the mission it is best suited for isboosting heavy payloads into orbit. Which is exactly the mission that the enviromentalist and the nuclear test ban treaty will prevent. Orion has excellent thrust, which is what you need for lift-off and landing. Unfortunately its exhaust velocity is pretty average, which is what you need for efficient orbit-to-orbit maneuvers.
Having said that, there is another situation where high thrust is desirable: a warship jinking to make itself harder to be hit by enemy weapons fire. It is also interesting to note that the Orion propulsion system works very well with thebomb-pumped laser weapons system.
Each pulse unit has a radiation case that channels the initial blast upward towards the pusher plate. Along the way it vaporizes a solid chunk of propellant and accelerates it to the plate. The device is basically a nuclear shaped charge. Each charge accelerates the spacecraft by roughly 12 m/s. A 4,000 ton spacecraft would use 5 kiloton charges, and a 10,000 ton spacecraft would use 15 kiloton charges. For blast-off, smaller charges of 0.15 kt and 0.35 kt respectively would be used while within the Terra's atmosphere. The air between the charge and the pusher plate amplifies the impulse delivered. The propellant is tungsten, the channel filler is beryllium oxide, and the radiation case is uranium. A 5 kiloton charge is about 850 kg.
So the x-rays and other radiation from the nuclear explosion are channeled by the x-ray opaque uranium up into the beryllium oxide channel filler. This absorbs the radiation, converting it into heat. The heat blasts upward, flashing the tungsten propellant plate into a jet of tungsten plasma. The jet hits the pusher plate, accelerating the spacecraft. The jet is confined to a cone about 22.5 degrees. It is estimated that 85% of the energy of the nuclear explosion can be directed in the desired direction.
A pulse unit that was not a shaped charge would of course waste most of the energy of the explosion.
Tungsten has an atomic number (Z) of 74. When the tungsten plate is vaporized, the resulting plasma jet has a relatively low velocity and diverges at a wide angle (22.5 degrees). Now, if you replace the tungsten with a material with a low Z, the plasma jet will instead have a high velocity at a narrow angle. The jet angle also grows narrower as the thickness of the plate is reduced.
This makes it a poor propulsion system, but an effective weapon. Instead of a wall of gas hitting the pusher plate, it is more like a directed energy weapon. The process was examined in a Strategic Defense Initiative project called "Casaba-Howitzer", which apparently is still classified.
The following table is from a 1959 report on Orion, and is probably a bit optimistic. But it makes for interesting reading. For more in depth calculations of an Orion rocket's specific impulse, read page 1 and page 2. But be prepared for some heavy math.
In other words, if you can believe their figures, the advanced Orion could carry a payload of 1,300 tons (NOT kilograms) to Enceladus and back!
NASA has been quietly re-examining ORION, under the new name of "External Pulsed Plasma Propulsion". As George Dyson observed, the new name removes most references to "Nuclear", and all references to "Bombs."
| Interplanetary Ship | Advanced Interplanetary Ship | |
|---|---|---|
| Gross Mass | 4,000 tons | 10,000 tons |
| Propulsion System Mass | 1,700 tons | 3,250 tons |
| Exhaust Velocity | 39,000 m/s | 120,000 m/s |
| Diameter | 41 m | 56 m |
| Height | 61 m | 85 m |
| Average acceleration | up to 2g | up to 4g |
| Thrust | 8e7 N | 4e8 N |
| Propellant Mass Flow | 2000 kg/s | 3000 kg/s |
| Atm. charge size | 0.15 kt | 0.35 kt |
| Space charge size | 5 kt | 15 kt |
| Num charges for 38,000 m | 200 | 200 |
| Total yield for 38,000 m | 100 kt | 250 kt |
| Num charges for 480 km orbit | 800 | 800 |
| Total yield for 480 km orbit | 3 mt | 9 mt |
| Δv 10 km/s Mass Ratio (Payload) | 1.2 (1,600 tons) | 1.1 (6,100 tons) |
| Δv 15.5 km/s Mass Ratio (Payload) | 1.4 (1,200 tons) | 1.1 (5,700 tons) |
| Δv 21 km/s Mass Ratio (Payload) | 1.6 (800 tons) | 1.2 (5,300 tons) |
| Δv 30 km/s Mass Ratio (Payload) | 2.1 (200 tons) | 1.3 (4,500 tons) |
| Δv 100 km/s Mass Ratio (Payload) | cannot | 2.2 (1,300 tons) |
| Delta-V | Mission |
|---|---|
| 10 km/s | Terra surface to 480 km Terra orbit |
| 15.5 km/s | Terra surface to soft Lunar landing |
| 21 km/s | Terra surface to soft Lunar landing to 480 km Terra orbit or Terra surface to Mars orbit to 480 km Terra orbit |
| 30 km/s | Terra surface to Venus orbit to Mars orbit to 480 km Terra orbit |
| 100 km/s | Terra surface to inner moon of Saturn to 480 km Terra orbit |
Rhys Taylor's 3D Orions
Master Artist Rhys Taylor recently made some 3D images and a short movie about a hypothetical Orion drive spacecraft (He is using the amazing free 3D rendering package called Blender). In order to avoid destroying the launch site, the spacecraft is boosted a few miles into the air by Space Shuttle style strap on solid rocket boosters.
Mr. Taylor's current project is to create images of an alternate history where American (I'm sorry: USAian) and Soviet Orion drive battleships fight around Callisto.
I have some of his work in the art gallery.
Mr. Taylor's current project is to create images of an alternate history where American (I'm sorry: USAian) and Soviet Orion drive battleships fight around Callisto.
I have some of his work in the art gallery.
William Black's 3D Orions
Here are some more CGI 3D rendering of Orion concepts created by Master Artist William Black.
Photon
Art by Frank Tinsley
The momentum of a photon is p = E/c, where E is the energy of the photon. So the thrust delivered by a stream of photons is ∂p/∂t = ∂E/∂t/c. This boils down to:
F = P/c
P = F * c
where:
- F = thrust in Newtons
- P = power in joules
- c = speed of light in a vacuum (3e8 m/s)
Solar Moth
Solar thermal rocket. 175 meter diameter aluminum coated reflector concentrates solar radiation onto a window chamber hoop boiler, heating and expanding the propellant through a regeneratively-cooled hoop nozzle. The concentrating mirror is one half of a giant inflatable balloon, the other half is transparent. Propellant is hydrogen seeded with alkali metal. The advantage is that you have power as long as the sun shines. The disadvantage is it doesn't work well past the orbit of Mars and the exhaust velocity is pathetic. This might be carried on a spacecraft as an emergency propulsion system, since the engine mass is so miniscule.
Art by Frank Tinsley
Painting by Professor Sol Dember
THS Fusion Pulse
THS Fusion Pulse. Fictional inertial-confinement fusion drive from the game GURPS: Transhuman Space. Like the VASIMR it has "gears", one increases specific impulse (exhaust velocity) at the expense of thrust.
VASIMR
Langganan:
Postingan (Atom)
Dynamic Periodic Table
Popular Posts
-
Engine List On This Page Introduction Watch the Heat "Plasma Drives" Popular Conceptions The Drive Table Aluminum-Oxygen che...
-
Pendahuluan Matahari yang setiap hari memancarkan sinarnya ke bumi dan juga ke planet-planet lain yang ada pada tatasurya kita, adal... -
KAPAGEN, the Tariel Kapanadze's generator by Jean-Louis Naudin created on may 28, 2010 - JLN Labs - Last update July 5, 2010 Tout...
-
Nanopartikel saat ini menjadi pembahasan yang sangat luar biasa oleh para ilmuwan. Karena sekarang ini dituntut segala prodak harus dalam ... -
Para peneliti di University of California Los Angeles (UCLA) berhasil mendemonstrasikan fusi nuklir dengan sebuah reaktor mini. Seth J. ...
Hi-Tech Hydrogen Plasma © 2011 Theme made with the special support of Maiahost for their cheap WordPress hosting services and free support.