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I was just reading about the whole Orion project and the one scary thing that I took out of it, is that we won't be back to the moon till after 50 YEARS after the first moon landing!
Why is it called tourist season, if we can't shoot at them?
Because we wasted time/resources on the shuttle. If the plans it replaced had been followed through we would have been on Mars long ago using nuclear rockets, which were well proven before the moon landings.
Dr. Mordrid ---------------------------- An elephant is a mouse built to government specifications.
I carry a gun because I can't throw a rock 1,250 fps
Did Freeman Dyson (the original project manager, and perhaps in the top 10 of british scientists - ever) not launch a critique on nuclear rockets reciently?
The 'old' orion project was for ship to be nuclear powered -http://en.wikipedia.org/wiki/Project..._propulsion%29 To launch it (as per Niven/Pournelle's 'Footfall'), would have killed many people from fallout launch. It would have requied dozens of shuttles to build the thing. It had to be tens of thousands to millions of tons to work. These tons could not be launched with nuclear launch vechiles.
A note on why teh project was shelved:
Freeman Dyson, group leader on the project, estimated back in the '60s that with conventional nuclear weapons, each launch would cause fatal cancers in ten human beings from the fallout (note that this estimate is disputed- see radiation hormesis). The United States Government concurred and decided that because of the danger to human life and the danger to electronic systems on the ground (from electromagnetic pulse) to shelve the project.
Project Daedalus was an enhancement to this - with a top speed of 10-15 %C - with C being the speed of light!!!!
Hmmm...smaller Orion spaceships (and such is depicted on Wikipedia) were launching on conventional rockets, switching to nukes only in very upper atmosphere (Google for more, there are really fun sites there)
Protocols call for launch on a chemical rocket with the NTR only firing up after leaving Earth orbit. Nuclear powered generators have been used for ages in missions like Voyager, Gallileo etc. using Radioisotope Thermoelectric Generators (RTG) and the next Mars rover will also use one to get around solar panel degradation and winter shutdowns.
Two major, and related, problems were identified during the Rover/NERVA program:
1. core disassembly due to vibration, accompanied by loss of material into the propellant flow.
2. loss of fuel matrix uranium and carbon due to coating errosion and cracking.
The first problem was resolved by an improved design that reduced vibration and matrix cracking. The second problem, fuel element corrosion, was more difficult at the time.
Given todays materials, such as metallic ceramics, these problems would not exist.
It would be amazing to see - provided the engine were fired only in space.
currently, it would take about 900 shuttle launches go get enough mass up there to assemble the thing though.
Plus the risk of launching that many uranuim bombs in dozens of shuttle flights would be a terrifying prospect.
Launching the whole lot from earth would requre a stupendous amount of energy in one launcher - something like the equivelent of every booster made by the US in the history of spaceflight!
The original plan was to use conventional explosives to lift it a few dozen feet (to protect the shield/damper systems), then start useing nukes right away in the earths atmosphere- though there is where people start to die from fallout and the mag pulse issue.
currently, it would take about 900 shuttle launches go get enough mass up there to assemble the thing though. Plus the risk of launching that many uranuim bombs in dozens of shuttle flights would be a terrifying prospect.
Bullhockey. NTR rockets use a much smaller core than you presume (Pratt & Whitney Triton NTR on the right for scale);
15,000 lbs, about 6,800 kg, for the whole engine including the reactor core at the top.
The shuttle could almost carry two of them to orbit. The heavy lifter being designed by NASA will carry ~120 metric tons, so carrying a power module with several of these would be a cakewalk....not that this would be necessary.
Also: "uranium bombs"? You're showing a basic misunderstanding of how nuclear weapons and reactors work.
Reactors have neutron moderators; graphite, beryllium oxide etc., as part of the core structure. This prevents them from exploding in a nuclear fashion because they absorb the neutrons that would make the core explode like a bomb. It takes a very high, and rather tightly controlled from the timing standpoint, neutron flux combined with a very high compression of the bombs core (uranium, plutoinium, neptunium etc.) to make a nuclear bomb explode.
Chernoble, TMI ect. "exploded" because of superheated steam overpressure and/or the loss of cooling which causes a meltdown and vaporization of its surroundings. Modern reactors like PBMR or CerMet cannot do this. Even if they lose all their coolant (usually helium or some other inert gas, but in a rocket a propellent like H2) they don't melt down. Their temperature stabilizes at a known level set by the design and they just sit there doing nothing; thermally hot, but stable. Since they also have external neutron absorbers that can be brought into play bringing them down even further isn't a problem.
The steam turbine on the other end of the facility is what could "blow up", and you have several of those in every non-nuclear power station.
Many space reactor designs incorporate the fuel in a metal-ceramic core with neutron moderators included in the matrix, making them even safer as the ceramic is far less likely to break down from either heat or stresss than any other core material. Encased in a strong vessel designed for the purpose these would very likely survive re-entry intact after a launch failure.
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