Lockheed Martin to Build Nuclear Powered Spacecraft

LouisvilleDebugger writes "The BBC reports that Lockheed Martin have received a $6M contract to develop the nuclear powered JIMO, or Jupiter Icy Moons Orbiter. (According to the NASA project site, the first probes would not launch before 2011 due to development lead time.) On arrival at Jupiter, the extra power allows the probe to orbit each of three of the Galilean moons (Ganymede, Callisto, and most challenging from a radiation exposure standpoint, Europa) in turn, presumably helping to establish the possibility of liquid water and hence, life within the Jovian system. JIMO is a sub-project of Project Prometheus, initiated by NASA this year for the purpose of demonstrating that nuclear powered and propelled spacecraft may be safely designed and tested."

Comments

Re:safe?

[Mr2cents]

I'm pretty sure the material is well-protected. Also, nuclear-powered space-probes have already been launched (V'ger, Viking landers too I think).

Re:safe?

[T5]

Nothing's completely safe. Fossil fuels aren't safe. Hydrogen isn't safe. Cows' bad breath will be the death of us all. Life is a risk-management exercise. So is designing space vehicles.

I work with some of the folks who are responsible for safety matters regarding hazardous/radioactive material aboard spacecraft. Believe me when I tell you that the utmost importance is placed on the "what-if's" of any given launch failure mode. The containers that house the radioactive material are ridiculously well scrutinized and tested, the failure scenarios are taken into consideration, including atmospheric dispersion of debris from a launch failure.

We've used plutonium powered modules for years now as a source of long-lasting (30 years or so) electrical power. Those capsules are some of the toughest, most durable, explosion-proof, reentry-proof items ever created.

For example, for one space mission, 25 sample power capsules were made for testing by using them as artillery projectiles fired by a cannon into a solid concrete wall. This induced many times the stress these capsules would ever see in even the most horrific failure of the launch vehicle. Of the 25, only one showed any sign of a stress-related crack. This tiny crack set into motion a full review of the capsule manufacturing process, a study of the atmospheric effects of a failed launch vehicle, and other safety-related processes that delayed the launch for about a year.

Whereas these newer power sources are going to be a challenge, they'll be well thought out, or they won't go.

Re:Io

[Manhigh]

The radiation environment at Europa is a challenge to design around. Sending the craft to Io would probably require so much more radiation shielding for the electronics (ie weight) as to make the mission infeasible.

Also, recent studies have indicated that Callisto and Ganymede might contain subterranean water, making the possibility of life greater there than at Io.

Cassini (the Saturn probe) was nuclear

[Jon Abbott]

It looks like nobody has said this yet, so I'll pitch in -- the Cassini space probe, which was launched on October 15, 1997, was also nuclear-powered. There were protests around NASA right before the launch took place, but it went up anyway without a hitch.

According to JPL's Cassini "safety" page, they explain that the probe is powered by three radioisotope thermoelectric generators (RTGs) which provide energy by the natural radioactive decay of Pu-238. This isn't fission or fusion at work, but merely the harvesting of heat generated by the radioactive decay. The big question for environmentalists (and NASA) was whether these RTGs would remain contained in the event of a launch disaster.

The big difference between the RTGs of Cassini and the nuclear technology in JIMO is that JPL wants to have a full-fledged nuclear fission reactor this time around. This would obviously provide a lot more power for the mission, at the expense of extreme public scrutiny. It will be interesting to see how this situation pans out.

Re:Cassini (the Saturn probe) was nuclear

[morcheeba]

Very close. Cassini and virtually all other deep-space probes used RTGs because solar power is not nearly as effective at such great distances from the sun than on earth.

The real big difference is that they're now using nuclear to provide propulsion. The ion drive is really cool (but not because I wrote a little software for one of the early test satellites :)

To develop thrust in space, you basically have to eject some sort of particle with a given mass and speed. The traditional approach uses rocket fuel or hydrazine as the mass, and uses the potential energy of the chemical bonds to provide the velocity. Ion drives bring just the mass portion of the equation on the spacecraft (remember, it's insanely expensive to lift weight into space). To provide thrust, the ions are accelerated using electricity -- electricity is free near the earth, or in the case of deep space probes, can be generated by nuclear means far more efficiently than other means.

So, to summerize, in traditional systems, thruster mass and energy are closely coupled (i.e. chemical reaction), while in ion drives, the two are seperated so that the most efficient storage methods can be used.

Nuclear Propelled, Not Powered, Is The Big Deal

[reallocate]

Lots of spacecraft have been nuclear powered. This one will use nuclear energy to create propulsion. That's the new part.

Re:For 6 Million?

[wulfhound]

It's a design study, not the building of a complete operational spacecraft.

The pessimist in me says this one will be cancelled long before it ever launches :(

Re:how does nuke==propulsion in space?

[Manhigh]

Electric Propulsion (Ion Propulsion)

Take Xenon or Krypton, use some electrical energy to ionize it, and use some more electrical energy to propel the ions out the back of your spacecraft much faster than you could ever propel the products of chemical combustion. Thus you get more momentum, gram for gram of propellant, than you would get from chemical propulsion.

Solar electric propulsion has been done before, such as Deep Space 1. But for going out to Jupiter with such a large payload, the Sun's energy is just not enough.

Yes

[Keebler71]

Yes... this IS completely safe. First off, most people have no idea what nuclear power for space really means. This includes the poster, as the article mentions both nuclear propulsion and nuclear power which are two very different things. This link does a pretty good job of explaining various space nuclear power programs.

Oh, and for all those who believe that we should be designing a manned mission to Mars, let me be perfectly clear:

The only way we will get humans to Mars will be using nuclear propulsion and nuclear power sources(RTGs). Period.

And for those who question the safety of launching RTGs... this link describes the cases where this has already happened. RTGs have survived abort detonations of REAL missions right after launch with no radiation leakage. They have also survived re-entry (Apollo 13) with no leakage. The safety technology is mature and works.

This is our only ticket for orbitter missions to the outer planets.

Space-based fission reactors

[mpaque]

There's more information on space-based reactors to b e used in the Jupiter mission at:

http://spacescience.nasa.gov/missions/prometheus .h tm

The reactor uses slightly enriched uranium, not plutonium, and is launched 'cold'. The uranium 'fuel' is much less toxic than plutonium. This type of fuel cannot be used to construct a fission bomb, as it contains far too low a concentration of U-235 to produce a nuclear explosion.

The reactor is launched 'cold', in a shut down state. That means that during launch, there will be no fission reaction products present. The reaction products are the biggest hazard with nuclear fuel, being both radioactive and chemically reactive, prone to dispersing throughout an environment if released. (Radioactive iodine and cesium isotopes being probably the best known examples.) The reactor is not started up until the spacecraft is on an interplanetary trajectory.

This is not a new technology. The SNAP-10A space reactor power system was launched in 1965. Methods for protecting and encapsulating the fuel elements to prevent dispersal or leakage are well known and tested. (These methods will survive explosions during the launch, as well as uncontrolled re-entry from orbit.)

Re:Space-based fission reactors

[Aglassis]

If I had points I'd mod you up.

You are absolutely right. What many people fail to recognize is that there are different levels of radioactivity. If a radionuclide has a long half life it will be less radioactive in the short term. In particular, U-235 and 238 with hundreds of million year half lives (U-238 in the billions) will have very low radioactivity compared to a fission product which may have a fraction of a second half-life. If you don't start up the reactor until it is safely in orbit, then there will be no fission products, and even if it did burn up in the atmosphere, it would have too low radioactivity to even notice.

Clarifications

[gratefully dead]

As mentioned earlier, there seems to be some confusion about what sort of nuclear power we are talking about.

There are three types of nuclear "power" sources in space.

Radioisotope power- this generates electricity because the decay of the isotope heats a thermocouple junction that generates a voltage. I'll bet this is the kind they are using on the spacecraft in question, and it has been used on many other spacecraft, including the Voyager series. Not much isotope is needed, so even if the spacecraft crashes, minimal contamination would occur.

Nuclear reactor power- another way to generate electricity in space is to have a full fledged nuclear reactor onboard the spacecraft. These designs are *very* cool. Generally they use liquid sodium as the conduction medium. Remember, mass is the determining factor in the design. To my knowledge these have never been actually used in space.

Nuclear powered rocket- the most cool rocket ever. Uses a nuclear reactor, that has hydrogen gas "fuel" running through it, superheating that gas. The gas is then ejected out the nozzle at super high speed to provide thrust. There is no electricity generation involved. As mentioned earlier, these rockets are banned by a treaty. None have every launched to my knowledge.