Update on Project Prometheus

Aglassis writes "It appears that NASA is not backing down from their nuclear space initiative. Project Prometheus has recently started a new web page (under JPL) and NASA is finishing up a period of public comment (last session today). Currently Northrop Grumman is contracted to begin preliminary design of the spacecraft until 2008 for NASA (the reactor will be built by the Department of Energy's Division of Naval Reactors--the folks who control all US submarine and aircraft carrier nuclear reactors). Early specs are that it will be 60 meters long, have a 30,000 kg mass, use a 100 KW reactor using Brayton cycle gas turbines, be powered by ion thrusters with a 7000 second specific impulse, and have a science payload of 1500 kg. Early mission plans for Prometheus 1 (Jupiter Icy Moons Orbiter) indicate that the spacecraft would orbit Callisto, Ganymede, and Europa individually, and perhaps have a lifespan of about 20 years."

Comments

Brayton cycle

[worst_name_ever]

Interesting that they would pick a Brayton cycle power generation scheme. Since it's open-loop, that means you limit the lifetime of your vehicle to however much working mass - not reaction mass, that's probably xenon in this case - you have on board. Of course the limiting factor might in fact be reaction mass after all, in which case it actually makes sense to have an open-loop reactor and reap the benefits of a simpler system.

Disclaimer: I am not a rocket scientist.

Re:Brayton cycle

[Smidge204]

There are open and closed versions of the Brayton cycle engine.

=Smidge=

ahhh they stabilized it

[Anonymous Coward]

So they finally figured out how to stabilize naquandria...

Re:ahhh they stabilized it

[Fadeproof69]

Bah! I, for one, welcome our new Go'auld overlords.

Thank god

[QuantumG]

Finally, we can make some real space vehicles. Fission is the most energy dense technology we have.. it's what we should be using in space. When fusion comes along we may well have something better, but until then we should use what we have.

Re:Thank god

[puzzled]

Coal is somewhere between one and thirteen parts per million Uranium. You can google and check the math but these numbers are not out of line:

We put twenty five *tons* of bomb grade Uranium 235 into the air each year with our current coal consumption. U235 is .72% of naturally occuring Uranium which means we're putting up about 3,500 tons of U238 as well. U238 which gets hit by neutrons from cosmic rays becomes ... Plutonium.

http://greenwood.cr.usgs.gov/energy/factshts/163 -9 7/FS-163-97.html

Don't tell any tree hugging antinuclear activists, but our most common form of electricity production will *always* produce more radiation than the most horrific nuclear fuel accident. Changes the picture a bit, doesn't it?

Its all cold war BS that we don't have nuke powered space vessels to take advantage of the 1,000X energy density improvement over chemical fuels. I hope this comes to an end soon ... I want fast Mars shots before I'm too senile to appreciate them.

Re:Thank god

[SidV]

Thank Jeff that when you take a small mass of radioactive material that gives off lethal amounts of radiation and spread it over a large geographic area you cannot get a lethal exposure.

In other words the background radiation of the debris area was less than the natural background radiation of natural Uranium rich areas like Western Africa, or in fact many parts of Canada, which have higher radiation levels than the debris area.

JPL

[tyleroar]

Project Prometheus has recently started a new web page (under JPL)

Wow. Am I the only one that thought the JPL must be some license agreement like the GPL, and the wondered why the hell a web page needed to be released with a special license?
Jet Propulsion Labratory

Re:Oh great

[Travoltus]

"Prometheus Nuclear Systems and Technology will focus on enabling NASA missions by researching and developing nuclear sources that will provide power to innovative scientific instruments and robotic systems, large and small propulsion systems that run on electricity and high-speed communications systems. The nuclear power sources would allow us to extensively explore our closest celestial neighbor, the Moon, as well as Mars and other destinations. Eventually, these power sources would support human explorers as they travel through space and explore other worlds.

The first proposed mission within Prometheus Nuclear Systems and Technology would be a mission to Jupiter, the Jupiter Icy Moons Orbiter (JIMO), which represents a new class of mission capabilities far beyond those possible with current power and propulsion systems. Powered by a space nuclear reactor and propelled by electric ion engines, the spacecraft would make up-close, long-term orbiting visits to three of the solar system's most intriguing moons- Europa, Ganymede, and Callisto. Beneath their icy surfaces, these moons may contain oceans of water that could have provided an environment that may have harbored life."

http://prometheus.jpl.nasa.gov/index.cfm?pageL1= mi ssions

Beats the heck out of me what that has to do with militarizing space. Besides, IMO, nuclear power is a lot less environmentally dangerous than other power sources except maybe solar energy (which might not work when you're x billion miles from the sun).

Re:Before you ask ...

[dotslashdot]

Hopefully they won't mess up and forget to turn on some really important flag in the kernel, only to discover none of their software is compiled for USB.

Is this science fiction?

[John Seminal]

Because there ain't no way the Bush White House is paying for this.

http://prometheus.jpl.nasa.gov/contentImages/Blimp _over_Titan211_br.jpg

If that above picture happens in my lifetime, I will drop a load.

I hope they start with something more resonable than this. A big project will get bloated and is less likely to happen. Instead of going to Jupiter, how about getting to Mars with a little more reliability, with people?

Re:Oh great

[QuantumRiff]

what do you think absorbs the readiation from the sun? (hint, its our atmosphere) that big ball in the sky that is the solar systems largest reactor (although its fusion, not fission). Honestly, do you think it's light that heats the earth? no, it radiation. Any radiation from a little spacecraft up in space is miniscule!

Why, snails could move faster ...

[2TecTom]

than the real progress NASA makes.

IMHO, it's a real shame projects like these aren't far more international in scope, open to all bidders, and funded from a futures type trust and traditional venture capital funding, as well as grants and taxes. Heck, most of these projects will pay back in spades if the new technologies were only properly licensed.

It simply amazes me how we have so many business geniuses, but not one of them has even considered space as the next new continent. What ever happened to good old American ingenuity and initiative, eh? Why have we apparently just given up our collective dreams of space exploration and development? Any one care to explain?

Re:Why, snails could move faster ...

[Daniel Dvorkin]

Don't blame NASA. I guarantee you there are a shitload of NASA scientists and engineers who are chomping at the bit to build this thing, and have been for decades. It's the politicians who make the spending decisions you should blame, and more generally, the voters who elect those politicians; if it weren't for our general loss of national will as regards space exploration after we beat the USSR to the Moon, we'd have a fleet of nuclear-powered spacecraft moving both cargo and people all over the Solar System by now.

It simply amazes me how we have so many business geniuses, but not one of them has even considered space as the next new continent.

Because the vast majority of businessmen, "geniuses" or not (mostly not) are incapable of thinking past next quarter's results. The potential ROI on space travel is huge, but it's also very long-term. Interesting that you mention "new continent" as an example -- it's worth remembering that the early voyages of the Age of Exploration were done on government funding. I think the lesson here is pretty obvious.

Heat Sinks / Spreaders?

[reality-bytes]

I don't know the ins and outs but I'd imagine that if you have a nice chirpy nuclear-reactor to generate power, taking photovoltaics (solar panels) with you too would be rather pointless. - PVs would cost extra to put into space to start with and would also need trickery to align them with the sun.

Having glanced at the picture, I'd suggest it is more likely that the big flat panels are heat dissipators (heat-sinks) to get rid of the excess heat from the nuclear reactor. I presume that in space there is no conduction of heat away from the vehicle, only radiation. And that you improve the radiation of heat by increasing the surface area.

Re:Heat Sinks / Spreaders?

[GileadGreene]

You are 100% correct. The large panels are radiators to dissipate excess heat. Large radiators are a standard feature in designs for space-going reactors, since the conversion from thermal energy to electrical energy is far less than 100% efficient.

Re:Heat Sinks / Spreaders?

[GileadGreene]

Different mode of operation. Most of the SNAP series are Radioisotope Thermoelectric Generators (RTGs). They produce thermal energy through radioactive decay of Plutonium (not fission!), and directly convert it to electrical energy using thermoelectric devices (the Peltier effect). I don't recall what the efficiency of thermoelectric conversion is off the top of my head, but I don't think it's that good - the main draw for using it the the lack of moving parts.

The move to fission is driven by a desire to get more power (even a large RTG will only produce a few hundred Watts, versus the kilowatts they expect to get from a reactor). I don't know exactly what the trade-offs are with using Brayton cycle vs thermoelectric (or thermionic) conversion. The Russians have flown a number of thermionic nuclear reactors (the Topaz series), and they seemed to work fairly well. I suppose it's possible that Brayton cycle reactors are more efficient than thermoelectric/thermionic conversion. But even if you assume a (highly unlikely) 90% conversion efficiency, a 100kW reactor would leave you with 10kW of thermal energy to dump. At this point it's probably worth noting that even the most high-power satellites we currently fly (the Boeing 702 comm-sat) operate on a mere 15kW of power. So you're talking about being able to radiate as much energy as most satellites generate in total. And as I said, that's based on some pretty optimistic assumptions about the efficiency of the Brayton cycle.

Re:Heat Sinks / Spreaders?

[GileadGreene]

In fact, you have to get rid of nearly all of the energy. Most of the energy that is converted to electricity is then used to operate something which then converts it back to heat (like a computer chip).

A good point. In fact, thermal design for spacecraft (at least at the preliminary stages) is typically carried out under the assumption that all of the electrical energy not leaving the spacecraft as RF radiation is converted into thermal energy.

The two energy expenditures I can think of that don't yield waste heat are the propulsion system (ideally), and the radios (again, ideally).

Unfortunately, both of those items are less than ideal. It's not uncommon for a spacecraft transponder to be on the order of 20% efficient (or worse). Likewise, the ion propulsion systems they are planning on using for Prometheus have an electrical->thermal conversion efficiency of around 70-80%. Which for a 20kW thruster (e.g. the proposed NEXIS thruster) means 4kW+ of waste heat.

Of course, I expect it would be possible to use a significant portion of that to heat the propulsion fuel.

The current proposals for Prometheus involve nuclear-electric propulsion rather than nuclear-thermal propulsion. I don't believe that heating the propellant in a NEP system helps (although I'm not really a propulsion expert, so I'm quite prepared to be corrected on this).

Re:Before you ask ...

[grozzie2]

You obviously missed that chapter. The M$ software is proprietary, and will be kept here as the 'secret weapon'. When we do finally stumble on the borg (or they stumble on us), we'll seed the collective by planting Windows onto a drone. It'll only take a few days, and the entire collective will consist of millions of machines working at 2 tasks, first trying to fight off infections from other drones, and second, trying to infect other drones. The collective will grind to a halt, and humanity will prevail, until next week's episode....

Project Orion was cooler, though

[armed ahmed]

Of all the atomic propulsion systems, project Orion is the one that struck me as 'reasonable', despite the atmospheric miniature nukes. The sheer payloads that it would enable make Orion the number one option for human spacefarization.

That said, I'm happy it never really materialized. Having a universe with a human population spreading effectively in it summons an eerie image on a spherically expanding brain-tumor to my mind...

...anyone interested in nuclear propulsion and the most avant-garde of rocketry, read about "Project Orion" if you already haven't.

http://isbndb.com/d/book/project_orion.html

This is not un-typical for Gummint projects

[leonbrooks]

Our local observatory (with live night-sky camera) is Gummint-funded. This leads to some interesting effects.

Much of their computing equipment has been scrounged - and doesn't appear on any equipment manifests - because there was no budget for it. They have a Pentium-90 driving (pointing) their main 'scope with a backup P-90 literally sitting on the next shelf in case it dies.

The few pieces of gear that they do get grants for are typically extremely fancy. On the rare occasions when ThePowersThatBe say "yes, you can have a computer to process the incoming images," then the cost of that actual computer system and absolutely nothing else is almost immaterial as long as it fits certain criteria.

So... in the room to the left of the one housing the P-90 sits a you-beauty glow-in-the-dark (well, not literally, it would cause backscatter) state-of-the-art box with double overhead ThermalTakes and all the trimmings. Just one. And I bet they crammed memory and disks into that baby's purchasing spec until the chassis groaned under the weight.

When Mark Shuttleworth gave his amazing talk at LCA2005, one of the things he mentioned was that the Yanks didn't want their astronauts (also going up in the Soyuz with Mark) flying to Baikonur in a rattly old Tupelov transport lest it unexpectedly drop out of the sky en route, but rather than come out and say so directly they came over all clever and simply pointed out that NASA regs forbade their astronauts to travel without seatbelts, which they knew the Tupelov wasn't fitted with. This was a mistake. On the day, the astronauts were marched out to the Tupelov, and aboard - and into a minibus in the cargo bay, where they sat and wore the minibus's seatbelts for the duration of the trip.

BTW, when the video DVD from LCA2005 gets published, bend heaven and earth to get yourself a copy. It's well worth-while for Mark's presentation alone ("Welcome to Khazakstan!"), and there are many other excellent presentations on it (Keith Packard explaining the sport of Window Hurling, for example, or E'dale demonstrating how to collapse a penguin's skull).

The point in that story which I wanted to use as an illustration here was that the minibus wasn't put aboard the transport for the astronauts' benefit. There was a budget for flying the Tupelov - pilots, fuel, landing fees and so on - but no budget for getting from the airport to where they were staying. So the van (which fell under the base's budget, so was financially covered) was fuelled up and driven aboard the Tupelov for use as a taxi while the transport 'plane was prepped for the return flight. In terms of working around bizarre regulations, NASA or not, the Americans really were amateurs playing in a professional field. (-:

Re:Risk

[cybercuzco]

Because this reactor will be designed to be in a rocket explosion. It will be launched before it goes critical. it wont even be turned on, and cant be turned on, until it is safely in orbit. Beyond that, there is alot more nuclear material in your nighborhood reactor than there will be in this thing.Not only that, but NASA launches over the ocean, water is a very good radiation shield. Thats why there are several nuclear submarines lying on the ocean floor that you arent worried about.

Re:The thing to do with Uranium

[crypto55]

In case you didn't realize, Uranium is the 8th most common material on the planet... Taking a few tons off of it won't do any good. There's enough uranium to last the damn planet for the next 2000 years at least. Don't argue with me, I researched the damn thing two months ago. :)

Gaseous Core Nuclear Reactor Rockets

[serutan]

On a related note, a few words about nuclear rockets. Back in the 50s and 60s some people, mostly science fiction writers, fantasized about nuclear powered rockets. In the 60s there was an actual prototype engine called NERVA. The idea was simply to use the reactor as a heat source to superheat a gas which would shoot out as rocket exhaust. The main drawbacks were the weight of the reactor core, the maximum temperature of about 3500 degrees C, and the radioactivity of the exhaust.

Here's a really interesting article that describes a design for a 100% reusable, non-polluting nuclear rocket based on the Saturn V form factor, capable of lifting 2 million pounds of cargo into orbit and returning to a soft landing. Just like in the old sci-fi movies. The design involves a gaseous core reactor, sometimes called a "nuclear lightbulb." It consists of a quartz bulb containing a cloud of uranium gas such as uranium hexafluoride, confined the center of the bulb by a buffer gas swirling around it. By adjusting the movement and pressure of the buffer gas, the compression of the UF6 can be finely regulated. When it is compressed to a critical state it heats up to about 25,000 degrees C, glowing intensely in the ultraviolet. Liquid hydrogen propellant pumped around the outside of the quartz bulb absorbs the ultraviolet light, becomes superheated, and shoots out of the nozzle. There is no leakage of radioactive fuel and no irradiation of the hydrogen. Completely clean burning. Such a rocket could burn for immensely longer times than any chemical rocket, providing the speed to get a manned mission to mars in a couple months. And not a skimpy mission, a spacious vehicle carrying 1000 tons of equipment, supplies and radiation shielding. Building a rocket like this wouldn't require any far-fetched technology, just some dedicated engineering.

I have never been a fan of nuclear reactors, but this thing sounds really good to me. The gaseous core has tremendous safety advantages over a solid core. The criticality of a cloud of gas is much easier to control and is to some extent self-regulating. For example, the problem of "hot spots" would not exist, because in gaseous form any part of the UF6 that overheated would expand, losing pressure and quenching itself instantly. The author describes several safety features, both active and passive, for letting the gas depressurize into a storage container extremely fast. Even if a gas core nuclear rocket exploded in the atmosphere, it would release a small fraction of the amount of nuclides from a single 1950s H-bomb test.

NASA must have told Bush there's oil on Titan!

[mbkennel]

that's right, George, there's rivers and rivers of LIQUID HYDROCARBONS down there, and America's got the mineral rights!