Rockets!
Posted: Fri Jul 06, 2007 8:10 am
What are the possibilities of using Polywell as a rocket? What can be done? Relativistic electron beams are mentioned. What of this?
Hasn't the polywell already been used for fusion? What's this directly nonsense?Could Polywell be used for fusion directly?
For small scale applications and around Mars, solar power is fine. However, for larger applications, like a manned mission some people are proposing, or for missions for Jovian planets, solar power is not enough, and RTGs or even fission reactors would be needed. RTGs have been used for quite a long time now.According to this page, using solar powered ion engines they could slowly build speed while in range of the sun. It made an overall velocity change of 4.3 kilometers per second, and it could have gone faster.
Sorry, bad wording.Hasn't the polywell already been used for fusion? What's this directly nonsense?
Its called "Quiet Electric Discharge"Zixinus wrote:What are the possibilities of using Polywell as a rocket? What can be done? Relativistic electron beams are mentioned. What of this?
Yes, and concord was faster than a 747. Speed is not the most important thing in the world. It didn't make concord competitive.JoeStrout wrote:No, not by orders of magnitude. According to Jim Benson: "to the Moon in hours, to Mars in days, anywhere in the solar system in weeks." Nothing else even comes close.
Plus other pesky things. Like cost. Safety. Engineering experience. Ease of maintenance. Reliability. The last three simply cannot be pulled out of a hat. They require lots and lots of time. All the maths and power point presentations and even ground tests in the world won't change that. It's the same reason why carbon fibre has taken 30 years to get into civil aircraft in significant quantities. They simply didn't have the experience to trust it.Right, there's always a trade-off between thrust and Isp.
Because despite what Mr Bussard may believe or claim, aneutronic means LOW radiation, not NO radiations. Even if the intended main reactions do not produce neutrons, the unintended side reactions inevitably do. And there are truly severe problems flying anything in our atmosphere that's 'only a little bit' radioactive. The large 'super plane' SSTO has also been considered before, and rejected, for logistical reasons that have nothing to do with Isp.Why do you say that? I'd expect a polywell rocket to get you into orbit very handily
A factor of an hour or two in a six hour trip is not significant.Yes, and concord was faster than a 747. Speed is not the most important thing in the world. It didn't make concord competitive.
I recall that QED engines in particular were relatively high Isp and had enough thrust to get to LEO, and then some.Even the optimistic predictions for QED/DFP engines don't have high thrust and high Isp because there are usually fundamental problems with that.
Look up, there are papers regarding ideas of Polywell and space engines. They contain much more serious science then what the powerpoint presentation says.Yes a Isp of 4k-5k would be very nice - but the only place I've been able to find that claim for polywell derived engines is in your statements here and elsewhere.
And thus little required shielding. Perhaps it would not have to carry shadow shield mass measured in tens of tons, like most fission schemes.Because despite what Mr Bussard may believe or claim, aneutronic means LOW radiation, not NO radiations.
Of course not, it would require aneutronic, low-mass fusion technology. Aneutronic equals "wacked" among fusion researchers, and low-mass is impossible with most magnetic confinement schemesThe 'arc jet from hell' high thrust engine is also vapourware. Even with practically unlimited energy on earth, I have found no evidence that anyone is claiming to produce a engine of this type and class.
The concord was slightly faster than a 747 — barely more than a factor of 2. A QED (i.e. polywell) engine would be dramatically faster than chemical rockets, by a factor of 100 to 1000. The two situations are not even remotely comparable.ANTIcarrot wrote:Yes, and concord was faster than a 747. Speed is not the most important thing in the world. It didn't make concord competitive.
So, if you haven't even done cursory research into the topic, one wonders why you're speaking with such an air of authority. Start with the 2006 Valencia paper, and then follow the references. Of particular use are The QED Engine: Fusion-Electric Propulsion for Cis-Oort/Quasi-Interstellar (QIS) Flight, and The QED engine spectrum - Fusion-electric propulsion for air-breathing to interstellar flight.ANTIcarrot wrote:Yes a Isp of 4k-5k would be very nice - but the only place I've been able to find that claim for polywell derived engines is in your statements here and elsewhere.
Yes... so? I never claimed we'd be zipping to Mars tomorrow. But I do claim that polywell-based engines, if they work, will revolutionize spaceflight like no other technology (which would also have to go through a development period) can.ANTIcarrot wrote:Plus other pesky things. Like cost. Safety. Engineering experience. Ease of maintenance. Reliability. The last three simply cannot be pulled out of a hat. They require lots and lots of time.
Since you seem to be in direct disagreement with Dr. Bussard, I encourage you to read his papers (the space applications were not covered by the embargo) and point out where he has gone wrong.ANTIcarrot wrote:As I said at the start, an Isp of 5000 would be nice, but that's the very limit of open-cycle Gas Core Nuclear Rocket technology, which is pretty much the best 'conventional' design we could build today. Beyond that designs require either unobtanium for either the fuel (like antimatter) or the reactor walls (to contain the heat). I would personally need a little more explanation and some reasonably hard numbers (engine weight for example) before I accepted this as a reasonable prospect.
I still stand by my point. There are other considerations. In this case the most important is that Mr Bussard's work has (the last time I checked) not been peer reviewed. Until then, let us not forget, however appealing these designs they remain theoretical. And real engineering beats theory nine times out of ten.JoeStrout wrote:The concord was slightly faster than a 747 — barely more than a factor of 2. A QED (i.e. polywell) engine would be dramatically faster than chemical rockets, by a factor of 100 to 1000. The two situations are not even remotely comparable.
The Daedalus interstellar probe I believe had comparable performance. But then again so does pixie dust. We don't know how to build either, but we do know they'd work really well if we could build them. Paper designs always work better than real designs.You can propose other advanced systems, like nuclear thermal, and they will come a bit closer, but I don't think anything else seriously explored performs nearly as well as QED.
I know a little about rocket design, and I've been following pollywell since the Google video came out. However I'll admit that I haven't been doing so over the last few months, since the first four or five reports were basically identical. It seems I have some reading ahead of me.So, if you haven't even done cursory research into the topic, one wonders why you're speaking with such an air of authority.
The paper also seems to repeat the flawed claim that the reactor produces no neutrons.And BTW, 4k-5k is modest. The QIS paper mentions Isp up to 70k sec for electric propulsion, or over a million seconds for a direct-heating engine.
That we can both agree on.Yes... so? I never claimed we'd be zipping to Mars tomorrow. But I do claim that polywell-based engines, if they work, will revolutionize spaceflight like no other technology (which would also have to go through a development period) can.
1) Missing out on significant practical issues; without even saying he was leaving them as 'minor engineering problems for the student'.Since you seem to be in direct disagreement with Dr. Bussard, I encourage you to read his papers (the space applications were not covered by the embargo) and point out where he has gone wrong.
The neutron problem is not hard to solve. You use water as reaction mass. You use the reaction mass as shielding. It doesn't take much water to absorb most of the neutron energy. The water would act as a reflector as well.real engineering beats theory nine times out of ten.
An attitude contributable to the fact that the man definitely won't see the ground tests of the thing, let alone someone building a rocket out of it.1) Missing out on significant practical issues; without even saying he was leaving them as 'minor engineering problems for the student'.
You know what pisses me off? Emotional appeal. If you say "think of the children" then you are appealing to emotion, not reason.2) Even with the best engineering, aircraft fall out of the sky on a regular basis. With a large fleet of polywell driven SSTOs you would disintegrating radioactive fusion cores falling over farmland, cities, oceans and playgrounds (Think of the children!).
And has been right before too. He studied nuclear engineering for the single purpose to figure out how to use the heat generated by a fission (that's fission, not fusion) core as a rocket engine. His Nuclear Thermal Rocket design, called KIWI design was out on paper before Sputnik was lunched, and efforts were made by NASA to do it. No NTR rocket was ever lunched, but for reasons unrelated to the technical feasibility of the idea.3) Mr Bussard has been wrong before. The complete history of the ram-jet design makes for interesting reading.
Dude, HE'S A frick NUCLEAR ENGINEER AND PHYSICIST, not an artist. The papers were on budget too, so I don't think they could have afforded an artist. Furthermore, they are trying to make a science paper afterall, not a article in "popular mechanics".4) He comits the cardinal sin of not including any pretty pictures of what his spaceship might look like.
It's good to be sceptical, I'm one too (not very active one though), but do make more research.5) I'm a nasty suspicious b*****d, and don't take anything at face value.
And for all practical purposes, there will be no neutrons.The paper also seems to repeat the flawed claim that the reactor produces no neutrons.