One of the few good uses for solid rocket motors

[TallDave]

I bet there is more than one fan of the REAL Project Orion on the forum.

I think it's a great idea myself - but the side effects would be a bit... extreme. Especially on launch - that thing's going to dig divots that'll scatter fallout for hundreds of miles downwind getting airborne. Once they get a couple miles up and then to orbit it won't be so bad, but that first step's a killer.

Would the whole thing work? Judging by the video of a test-bed using conventional explosives, I think it would. I'd want to be a LONG way off when the thing's launched, though!

I've always assumed we would launch from Antarctica.

[GIThruster]

There have been decades of gas core nuclear rocketry over the last 4 decades.

Just none of it has been built, but there are thousands of pages to pour through.

Nuclear Light Bulbs are cool and happenin' if we ever have the will.

[rjaypeters]

Preferred solution: gas core nuclear thermal rocketry.

I haven't a clear understanding of how the nuclear part of the gaseous core reactor stays in the reactor. Does it? Can you point me in the right direction, please?

Some of our correspondents object to Project Orion fallouts and solid core reactors have some fallout, too. Is the gaseous core supposed to be cleaner, more efficient, what?

[GIThruster]

" Can you point me in the right direction, please? "

Just search the common words. Sandia has done work on this for decades.

http://en.wikipedia.org/wiki/Nuclear_lightbulb

[TallDave]

This is why we have no space program, because there's something in engineers, that at times they utterly lack common sense. There is no way an open cycle fission rocket could ever be built. If it could, the infrastructure for the bombs you throw out the back would cost many billions, and the security for handling it could cost trillions.

We can't even get a closed cycle fission motor built and flown. We're not even flying fission reactors for space power.

This kind of "brainstorming without the brain" is exactly why we have no human spaceflight program. People just don't pay attention to practicalities.

You're confusing practicalities with politics and legalities. Right now we have a ridiculously impractical chemical rocket program because it's politically acceptable. The costs to get a kg of payload into orbit would come way, way down under an Orion-type vehicle. I won't be terribly surprised if China thumbs its nose at the world and parks a carrier in orbit around Mars someday.

Throwing bombs out the back of a rocket is NEVER going to be sold to the public. They simply will not allow it. Likewise, it's a violation of current treaty and we're not going to see the treaty changed for the sake of human spaceflight. So why giggle at the notion of a completely unworkable idea? It wasn't ever a good idea!

The public of 2010 won't. But who in 1950 would have predicted today's society of open gay marriages and Internet porn? So who knows what the future holds. Anyways, the treaty wasn't really meant to cover spacecraft.

[GIThruster]

Dave, no joke, but I'm not confusing anything. Public servant engineers who don't EVER think about what their dreams cost, have saddled us with the dopey situation we have. SSTS costs 5X what it's next nearest most expensive system costs.

People who don't pay for a thing, or work for companies that have to function in fiscal responsibility, are NEVER going to be the people to design responsible space launch endeavors.

That's why we have to look to private enterprise to hook us out of the tragic position we're in with regards human spaceflight--because people who don't care about costs can NEVER be trusted to design transport systems of any kind.

[TallDave]

I agree, I'm just saying nuclear rockets aren't impractical so much as they're impolitic.

Unfortunately, the private sector has to work under the same unreasonable legalities and politics as the government. So until people are smarter they'll have to use crappy chemical rockets too.

http://en.wikipedia.org/wiki/Nuclear_lightbulb

That sounds very sexy, thanks for sharing. What does the specific impulse look like?

[GW Johnson]

The Project Rover nuke rocket program achieved ground test firings of solid core rocket engines from 1959 to 1973. The early models (Phoebus series) suffered severe nuclear core erosion and had very radioactive exhaust plumes. The final versions (NERVA series) did achieve control over core erosion, and thus actually had rather clean plumes, radiologically speaking. There were some even better designs that were never tested (Dumbo and Timberwind come to mind).

Rover also included a gas core program element divided into two basic approaches: the "nuclear light bulb", and an open-cycle gas core analog to Phoebus and NERVA. The light bulb designs are still limited by a physical solid surface or surfaces between the fission plasma fireball and the working propellant fluid. Peak Isps would be in the 1300-1600 sec range. The open cycle approaches had higher temperature and Isp potential, but were limited by propellant "transparency" to fission radiation: regenerative cooling was not enough, by far, above certain power levels.

The one that came within a year or two of being built and tested was a spherical transpiration-injection open-cycle system. They did plasma-phase criticality and control experiments with real gas-phase reactor cores. They did the powered plasma flow geometry tests that verified 1000:1 flow ratio hydrogen:uranium, which at their power levels and burnup rates, was as good as perfect containment. Plume radiation was therefore rather modest. Postfire, there was no radioactive core, just an "empty steel can". Accordingly, abortability was far, far better with this open-cycle gas core approach.

This thing was good for 2000-2500 sec Isp at "high" engine thrust / weight (not sure of figures, but I think it was well above 30). At higher Isp's, a closed-loop waste heat radiator was required in addition to the regenerative cooling. They thought the ultimate limit was around 10,000 sec Isp. The design target for the first-generation engine was 6000 sec Isp, at an overall engine system thrust / weight near 0.1, which was also predicated upon a 4000 deg R radiator technology (that we still do not have today because nobody has worked on it). This was the preferred nuke engine (NERVA was baseline) for the 1987 Mars mission, at the time Nixon cancelled everything manned outside Earth orbit.

All this stuff is still out there at the nuclear test site in Nevada. Some of it still "glows blue" at night, even after all these years. The specific location within the Nevada site is a place name "Jackass Flats". In addition to the Rover nuke rocket stuff, the Project Pluto nuclear ramjet stuff is also still out there at Jackass Flats, including the direct-connect ramjet test facility. That one is a whole 'nother story. They actually did test nuclear ramjets out there in the 60's. Few ever knew that, even fewer remember.

[TallDave]

10x chemical rockets is pretty good.

Estimates for Orion were for 10,000 - 1,000,000 Isp. I assume the range is so large because they looked at fission-fusion-fission bombs.

[JLawson]

I've always assumed we would launch from Antarctica.

But think of the penguins! They'd glow in the dark afterward!

(Hmmm, it's a penguin AND a night light...)

Launching off the icecap might be the best option at that. The vaporized water should quickly refreeze and drop out of the atmosphere, limiting spread of whatever particulates are left after the explosion. A sea launch doesn't seem like a great idea to me - the fireball would vaporize and cook a lot of sea life (not that there's anything wrong with poached dolphin) but I'd be worried about (a) wave/tsunami risks, and (b) downwind fallout.

The Nevada Test Site wouldn't be bad... but there'd be a lot of crap sucked up into the atmosphere. And what goes up in a fireball has to come down...

There's a lot of contaminants in seawater that wouldn't be found on the icecap (Flipper's never been sighted at the South Pole, for example) and if you're looking for a CLEAN launch I can't think of a better place.

[JLawson]

All this stuff is still out there at the nuclear test site in Nevada. Some of it still "glows blue" at night, even after all these years. The specific location within the Nevada site is a place name "Jackass Flats". In addition to the Rover nuke rocket stuff, the Project Pluto nuclear ramjet stuff is also still out there at Jackass Flats, including the direct-connect ramjet test facility. That one is a whole 'nother story. They actually did test nuclear ramjets out there in the 60's. Few ever knew that, even fewer remember.

Project Pluto - THAT was a (shudder) interesting concept. The assembly building is still there as well as the rail bed for the system used to get the ramjet to the test cell (which included a LOT of drill pipe to serve as high pressure air storage) but the pipes are long gone. Google Earth shows the test cell area at 36 48.98N, 116 8.52W, the assembly building at 36 48.9N 116 9.88W (approximately.)

Went out to the NTS close to 30 years back... biggest darn gopher holes I ever saw...

[GW Johnson]

"Pluto" was a low-altitude M3-ish cruiser with an essentially-infinite time on station, circling, waiting for the order to strike. Given the "go" code, it would fly to target and detonate its nuclear warhead. The hell of it is, the lethally-loud shock wave and the radioactive plume would have killed more people on the way to target, than the megaton-range detonation over target.

Vought (later LTV) in Dallas was the airframe prime, including the supersonic inlet. AEC was to supply the reactor core "combustor". Reactor supports operated within about 10 F of their material meltpoints. Core erosion and structure erosion was a real issue.

[choff]

Penguinzilla!

[rjaypeters]

GW Johnson: Was project Pluto the weapon that was supposed to cruise over the Soviet Union after dropping bombs and and use the eroded reactor core to salt the land with fallout?

Was it Oppenheimer who called it "technically sweet?"

If so, I submit this concept/device as one of the few inherently evil mechanisms ever created.

[JLawson]

Here's the article that was in Air & Space magazine.

It's one of those things that is, indeed, 'technically sweet' - but the actual implementation would have been horrible.

http://www.merkle.com/pluto/pluto.html