Power and Purpose in Space Without nuclear-powered spacecraft, we'll never get anywhere

NuclearSpace.com ^ | 12/10/02 | Robert Zubrin

[Brett66]

A manned 'External Pulsed Plasma Propelled' Vehicle approaches Mars. Image courtesy NASA

Power and Purpose in Space
Without nuclear-powered spacecraft, we'll never get anywhere

by Robert Zubrin, Mars Society

Wood, wind, water, coal, oil, gas, and nuclear energy: of those major power sources, only one—nuclear—can work in space. Like it or not, humanity is going nowhere, astronautically speaking, without the power of the atom.

Because of technical and political factors, nuclear technology has been confined to applications that produce rather little power, mostly in deep-space probes. Lacking nuclear energy as a robust and diverse option, for both propelling spacecraft and powering their on-board systems and instruments, we have been forced to make extensive use of solar power for systems and instruments and to rely exclusively on chemical rockets for propulsion.

Neither one is adequate. To power spacecraft instruments, the sun's thin rain of energy is of little use much beyond Mars's orbit. For propulsion, chemical rockets run up against the basic burden of space travel: weight. The cost of a space mission scales more or less proportionally to the mass of the spacecraft involved. Up to 90 percent of the weight of a typical chemical rocket at launch is propellant. So to keep this load to a minimum, propulsion experts choose chemical propellants whose reactions are very energetic. The more energy per unit mass of propellant, the less propellant needs to be carried, and the cheaper the mission will be.

Rocket engines fueled with hydrogen and oxygen have already come quite close to the practical performance limit of chemical propulsion. Spend all the money you want; you won't do much better. Nuclear reactors, on the other hand, pack a million times as much energy per unit mass as the best chemical fuels. The challenge, of course, is getting the power out usefully and safely.

Rest of article here:

Power and Purpose in Space

[Brett66]

Thought I better excerpt the article, they mentioned something about copywrites and such.

[Brett66]

Ping.

[Fish out of Water]

bump

[LibWhacker]

Bring back Project Orion!

[gorebegone]

[Badger1]

I worked a bit with Zubrin before he started his Mars Society project. He is a smart, focused guy who is the leading spokesman for manned Mars missions. I currently work in a propulsion laboratory where we are building prototypes of the in-situ propellant production plants Zubrin discusses in his article. However, there is currently no research or development going on regarding nuclear power usage in spacecraft that I know of. Which is a shame. Our current political climate driven by the radical environmentalists has made this type of research taboo for any company.

The last spacecraft we launched with the RTG's mentioned in Zubrin's article was the Cassini spacecraft (in 1997, and which I had the pleasure of working on). It took direct approval from President Clinton to launch that spacecraft with only a couple of pounds of radioactive material on board.

[Brett66]

Zubrin also designed the Nuclear Salt Water Rocket, which appears to be superior to even the performance of Orion. If we could build spacecraft based on that technology, the solar system would be our playground. I'm not holding my breath on that becoming reality anytime soon though......

[Badger1]

Zubrin also designed the Nuclear Salt Water Rocket, which appears to be superior to even the performance of Orion

Another technology that no research has been done on due to the aversion of radioactive materials.

[MeekOneGOP]

[RadioAstronomer]

The last spacecraft we launched with the RTG's mentioned in Zubrin's article was the Cassini spacecraft (in 1997, and which I had the pleasure of working on).

I was at KSC when all the protesters showed up due to the fact that the Galileo spacecraft had an RTG on board.

[Frank_Discussion]

While I suppose it isn't research in the area of nuclear power sources per se, but I know that Dr. Franklin Chang-Diaz's Mars rocket is banking on it. His engine design is called the VASIMR, and his test system is at Johnson Space Center in Houston.

[Badger1]

I was at KSC when all the protesters showed up due to the fact that the Galileo spacecraft had an RTG on board

The same protests happened before the Cassini launch.

[Badger1]

The VASMIR (Variable Specific Impulse Magnetoplasma Rocket) uses magnetic and electrical fields to heat a neutral gas and ejects it thru a two stage nozzle. It is a really good concept that can be throttled to achieve high thrusts and lower specific impulse or lower thrusts and higher specific impulse. However, the only way for this engine to get enough power to operate is with nuclear power.

[The_Victor]

Thanks for the ping. Bump to read later.

[Frank_Discussion]

"However, the only way for this engine to get enough power to operate is with nuclear power."

Quite So. That IS why I pointed it out, y'know. :-)

Thanks for the assist in defining the VASIMR for the thread, I was pressed for time when I posted previously, so I didn't go into it.

[RightWhale]

The problem is that these people don't have a clear idea of how to make gobs of money in space development. With all the technical expertise around, you'd think someone could do a present-worth analysis. Nuclear propulsion isn't necessary to make space development profitable, but it would increase the profit margin to unconscionable levels.

[Bush2000]

Whether or not you agree it's realistic or not, the problem has always been public perception of safety hazards in getting nuclear-powered spacecraft into orbit. My feeling is that we could mitigate the public health risks of nuclear crashes in several ways. First, we could set up a launch platform in the remote Pacific (instead of Florida) so that, if a crash occurs, the likelihood of nuclear contamination is minimal. The negative would be increased costs. Secondly, and perhaps orthoganally, we could launch most of our expected nuclear fuel separately as a single, concentrated payload, and store it in space. Shuttle launches could use conventional fuel to get into orbit and then load their reactors (perhaps the reactors could even be staged modules that "plug" into the shuttle) after docking in space. This would avoid the statistical likelihood of a contaminating crash resulting from launching multiple nuclear-laden craft. Something to think about.

[Badger1]

The main problem with any nuclear power system for spacecraft is political. Not only in how you get the fuel into orbit, but also the problem of testing the system on the ground. For example in my companies work on the Cassini spacecraft, we had to ship the spacecraft out of Colorado to JPL to put the RTG's on. Any testing of nuclear power generation systems are subject to tremendous amounts of legislation and the (guaranteed) possibility of protests. Until the political problems of nuclear power generation are worked out, there will be very little research in this area.

[techcor]

but it would increase the profit margin to unconscionable levels.

No such level. But I'll still maintain the future of space flight will be with nuclear isomers rather than with regular fission. The key will be to modulate the input wave (x-rays) to cause the nuclear isomer to give up it's energy quicker.

Two reasons for this belief. First, environmentaly speaking it will take less fuel, therefore less danger. Secondly, if we can tap nuclear isomers to release energy , we will probably find a way to store energy in them by pumping them up with a laser. Thus , the isomer becomes reusable, therefore increasing the profit margin to incredible levels.

[John Jamieson]

I really like Robert, but we still need a much better heavy lifter to get into orbit in the first place and that won't be nuke.