The Shuttle is certainly the best available replacement for itself.
Nonsense. The shuttle is very expensive; Buran was very expensive too. The Shuttle, when it finally retires (probably after the next fatal accident) will be replaced by expendable launchers.
The sad part is that apparently one of the reasons they stopped the Buran program was a relatively minor glitch, and politics.
No, Buran was stopped because it was ridiculous and useless. It was much more expensive than the expendable launchers they already had. They should never have built it.
You gotta wonder why NASA aren't cranking out Shuttles like Boeing crank out 747s. Any first year MBA will tell you that the key to funding any development that requires substantial upfront investment is to realize economies of scale in production.
The shuttle is expensive because of the army of people needed to operate it, not the cost of building the orbiters themselves. So mass producing orbiters is not a solution.
Bullshit. The military had to be dragged kicking and screaming to the shuttle. They were much more realistic about its chances of success than NASA was. NASA was the one pushing for the shuttle, since it was to be NASA's big moneypot after Apollo.
starts whining about how NASA is a big waste of money and is incompetent.
That wouldn't matter so much if NASA weren't (collectively) incompetent and a waste of money. They're an organization with no good reason for existing, which is the root cause of all the organizational pathologies we're seeing.
Every year, for decades, the budget shrinks and some more people die, retire or get laid off. The organization is slowly being hollowed out from within.
This is the normal mode of death of useless government organizations. It's hard to kill the programs outright, but they can be slowly eroded. NASA is still big enough to avoid outright closure, but that day is a lot closer than it used to be.
Enjoy... a paper proposing a colliding beam fusion reactor. Protons and boron ions are injected via oppositely directed beams into an FRC[...]
From http://www.aps.org/BAPSDPP98/abs/S6900.html:
Effects of Collisional Dissipation on the "Colliding Beam Fusion Reactor "
Martin Lampe, Wallace M. Manheimer (Naval Research Laboratory, Washington, DC 20375-5346)
Rostoker, Binderbauer and Monkhorst have recently proposed a "colliding beam fusion reactor" (CBFR) for use with the p-B11 reaction. We have examined the various dissipative processes resulting from Coulomb collisions, and have concluded that the CBFR equilibrium cannot be sustained for long enough to permit net fusion gain. There are many collisional processes which occur considerably faster than fusion, and result in particle loss, energy loss, or detuning of the resonant energy for the p-B reaction. Pitch-angle scattering of protons off the boron beam, which occurs 100 times faster than fusion, isotropizes the proton beam and results in proton loss. Energy exchange between protons and boron, which is 20 times faster than fusion, detunes the resonance. Proton-proton scattering, which is faster than fusion for all CBFR scenarios, Maxwellianizes the protons and thus detunes the resonance. Ion-electron collisions lead indirectly to a friction between the two ion beams, which is typically fast compared to the fusion process. Results of Fokker-Planck analyses of each process will be shown.
You're missing the point here. I was criticizing the notion that a non-breakeven fusion reactor would make a good rocket, since, like the Hall thruster or ion engine, it also needs a very large external power source -- so why not just use a Hall thruster and forget the fusion reactor?
Hall thrusters are different from ion engines, btw, in that they are not subject to the space charge limit that bounds the thrust density of the latter.
Yes, a nuclear engine that needs no large external power supply is another matter. But that's not what I was criticizing.
IEC, on the other hand, appears to be fantasy as a breakeven reactor, so it's not likely to be useful in any case.
That may be true for traditional electrolysis, but proton-exchange membranes are very much like fuel cells "running in reverse," and much more efficient.
Sorry, that's just bullshit. Traditional electrolyzers are quite efficient. The problem is that electricity is *expensive*. Even at 100% efficiency electrolytic hydrogen cannot come close to competing with hydrogen from large scale gasification of fossil fuels or biomass.
Natural gas to large customers is a hell of a lot cheaper than 14.4 cents per kWh. Electrolysis might make sense for niche applications, like off-grid, but for the economy as a whole it's a non-starter.
ion engines are low thrust and would have to be battlestar galactica sized to get higher thrust. I'm not sure of what you mean by a plasma engine - ion engines use plasma.
Plasma engines are engines that accelerate ionized gases in a way other than electrostatically. Hall thrusters, VASIMIR, etc.
Sure, ion engines have lousy acceleration, since they need a big power supply. But a non-breakeven fusion device would also need a big power supply, so it suffers from the same problem.
Fossil fuels are not renewable; therefore, that statement will only be true for a finite time. Who knows how long?
Certainly much longer than the previous poster's claim (2009, wasn't it?) Coal will last for centuries at current consumption rates; seabed methane is even more abundant. If you want to make hydrogen you can do that in a large fixed plant and react the CO2 with silicates to make carbonates. Hydrogen produced this way will have no global warming contribution, yet will be much cheaper than electrolytic hydrogen.
Electrolytic hydrogen is a tiny fraction of current hydrogen production. It's used when thermochemical hydrogen isn't available (for example, in spacecraft, or in very small scale applications where the thermochemical plant doesn't scale down well). On an economy-wide scale it would not be competitive.
I suspect that wind-electrolyzed hydrogen will become financially relevant before 2009.
This is very unlikely. Instead, it would be cheaper to get that hydrogen from gasifying fossil fuels, even if wind turbines can make electricity cheaper than coal-fired powerplants. Thermochemical hydrogen production is very convenient and cheap; electrolysis is not.
Electrolysis is grossly noncompetitive as a source of hydrogen. Even hydrogen from biomass is cheaper if the the cost of electricity is greater than 2 cents/kWh.
I got the 20,250,000 number because deuterium is an isotope of hydrogen which occurs naturally at a rate of about 1:4500 hydrogen atoms, but to make heavy water (D2O) out of regular water (H2O) you have to have both hydrogen atoms replaced with deuterium, making the natural heavy water ratio 1 in 4500^2, or 1:20,250,000.
But note that water molecules are constantly exchanging hydrogen atoms, so the deuterium atoms are being shuffled off to HDO molecules from D2O. The techniques that concentrate deuterium in water work on all the deuterium, not just the small fraction that happens to be in D2O molecules at any instant in time.
Remember, to use the duterium in the reactor you have to split the heavy water apart, which lessesn the net gain of the reactor.
Energy required to split off a D atom: a few electron volts.
Energy obtained from its fusion: several million electron volts.
Splitting heavy water (or even making it in the first place from ordinary water) is not a significant expense, in either money or energy, when it comes to operating a fusion reactor.
Why do we need fusion (or any non-pol energy source) when oil can do.
Perhaps because you can't fit a fusion reactor in a vehicle smaller than a large ship? There's an irreducible amount of shielding you need for even the cleanest fusion fuels. And making synfuels with fusion is simply noncompetitive.
The p-11B reaction will inevitably produce gamma radiation from the p + 11B --> 12C + gamma side reaction.
Achieving high energies in a device like this is possible, but maintaining the non-Maxwellian ion energy distribution in the face of Coulumb scattering (which has a cross section orders of magnitude higher than the fusion cross section), as well as other energy loss mechanisms like loss of ion energy to drag on the ambient cool electrons, is probably not feasible.
Producing fusion reaction at all is easy. It's been possible since Cockroft and Walton's work in the 1930s. Just build a sufficiently powerful accelerator and direct the beam of the appropriate ions at the appropriate target. You can buy modern versions of their apparatus that you can hold in your hand that produce orders of magnitude more neutrons than the IEC-based neutron generator. Small accelerators like this are lowered into oil wells every day to do neutron well logging.
But this approach (and very likely, IEC fusion) cannot produce breakeven, since the losses of beam ions that scatter will always exceed the fusion yield by a large margin.
Even very low energy neutrons will activate materials by neutron capture. Energetic neutrons will open up additional activation reactions, granted, but thermal neutron activation works just fine at producing radioisotopes.
That point is the usual conspiracy theoretic bullshit, though. Fusion would suck for most of the uses of oil (which is not used much for generating electricity in the US.)
Some of these nuts are actually pretty close to sustaining a reaction using this method.
No they aren't. Generating millions of neutrons per second is piddling. That's a fusion power of microwatts. If they're using kilowatts of power to generate microwatts of nuclear reactions then they're not even up to the level of beam-on-target neutron generators, a technology that's been available for over 60 years.
You can easily build an IEF device that generates neutrons. But then you can easily turn a van deGraaf generator into an accelerator that will produce neutrons.
What neither of these will do is produce more fusion energy out than goes into accelerating the ions. In the case of IEF, you lose energy when ions scatter without fusing and collide with the accelerating grid, or when they undergo charge exchange reactions with neutral gas molecules and the energetic neutrals fly off and hit the walls. The cross section for Coulomb scattering is far larger than the cross section for fusion, so a nonthermal ion distribution (such as here) tends to quickly degrade.
When launch costs are reduced by a factor of 100 ? And that will be when.. next week ? The truth of the matter is there is no readily apparent technology that will so much as reduce it by a factor of 10 in the next decade and in the meantime we will continue to launch. Seeing as that is the major budgetary issue regarding the station why not rotate crews while we are at it ? We have spent the billions to get the thing up there and we are just going to abandon it in the name of budget constraints when we will spend just as much after abandoning it ? Almost makes sense in an odd beuaracratic way.
The space station, and manned spaceflight in general, are useless at current launch costs. So, yes, it may be decades until launch costs are reduced by a factor of 100. All the more reason to kill the station, AND the shuttle, and tell the astronauts to go find jobs elsewhere. In the meantime we'll continue to launch on expendable rockets.
No, we won't spend just as much on ISS after abandoning it. ISS is the only remaining justification for the shuttle. In fact, keeping the shuttle from being cancelled is NASA's primary goal in building ISS. Cancel ISS and we save $3+ B per year being poured down the shuttle rathole, in addition to saving the cost of ISS support itself.
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This is the normal mode of death of useless government organizations. It's hard to kill the programs outright, but they can be slowly eroded. NASA is still big enough to avoid outright closure, but that day is a lot closer than it used to be.
You're missing the point here. I was criticizing the notion that a non-breakeven fusion reactor would make a good rocket, since, like the Hall thruster or ion engine, it also needs a very large external power source -- so why not just use a Hall thruster and forget the fusion reactor?
Hall thrusters are different from ion engines, btw, in that they are not subject to the space charge limit that bounds the thrust density of the latter.
Yes, a nuclear engine that needs no large external power supply is another matter. But that's not what I was criticizing.
IEC, on the other hand, appears to be fantasy as a breakeven reactor, so it's not likely to be useful in any case.
Natural gas to large customers is a hell of a lot cheaper than 14.4 cents per kWh. Electrolysis might make sense for niche applications, like off-grid, but for the economy as a whole it's a non-starter.
Sure, ion engines have lousy acceleration, since they need a big power supply. But a non-breakeven fusion device would also need a big power supply, so it suffers from the same problem.
Electrolytic hydrogen is a tiny fraction of current hydrogen production. It's used when thermochemical hydrogen isn't available (for example, in spacecraft, or in very small scale applications where the thermochemical plant doesn't scale down well). On an economy-wide scale it would not be competitive.
Electrolysis is grossly noncompetitive as a source of hydrogen. Even hydrogen from biomass is cheaper if the the cost of electricity is greater than 2 cents/kWh.
Energy obtained from its fusion: several million electron volts.
Splitting heavy water (or even making it in the first place from ordinary water) is not a significant expense, in either money or energy, when it comes to operating a fusion reactor.
Perhaps because you can't fit a fusion reactor in a vehicle smaller than a large ship? There's an irreducible amount of shielding you need for even the cleanest fusion fuels. And making synfuels with fusion is simply noncompetitive.
The p-11B reaction will inevitably produce gamma radiation from the p + 11B --> 12C + gamma side reaction.
Achieving high energies in a device like this is possible, but maintaining the non-Maxwellian ion energy distribution in the face of Coulumb scattering (which has a cross section orders of magnitude higher than the fusion cross section), as well as other energy loss mechanisms like loss of ion energy to drag on the ambient cool electrons, is probably not feasible.
Producing fusion reaction at all is easy. It's been possible since Cockroft and Walton's work in the 1930s. Just build a sufficiently powerful accelerator and direct the beam of the appropriate ions at the appropriate target. You can buy modern versions of their apparatus that you can hold in your hand that produce orders of magnitude more neutrons than the IEC-based neutron generator. Small accelerators like this are lowered into oil wells every day to do neutron well logging.
But this approach (and very likely, IEC fusion) cannot produce breakeven, since the losses of beam ions that scatter will always exceed the fusion yield by a large margin.
Even very low energy neutrons will activate materials by neutron capture. Energetic neutrons will open up additional activation reactions, granted, but thermal neutron activation works just fine at producing radioisotopes.
That point is the usual conspiracy theoretic bullshit, though. Fusion would suck for most of the uses of oil (which is not used much for generating electricity in the US.)
You can easily build an IEF device that generates neutrons. But then you can easily turn a van deGraaf generator into an accelerator that will produce neutrons.
What neither of these will do is produce more fusion energy out than goes into accelerating the ions. In the case of IEF, you lose energy when ions scatter without fusing and collide with the accelerating grid, or when they undergo charge exchange reactions with neutral gas molecules and the energetic neutrals fly off and hit the walls. The cross section for Coulomb scattering is far larger than the cross section for fusion, so a nonthermal ion distribution (such as here) tends to quickly degrade.
No, we won't spend just as much on ISS after abandoning it. ISS is the only remaining justification for the shuttle. In fact, keeping the shuttle from being cancelled is NASA's primary goal in building ISS. Cancel ISS and we save $3+ B per year being poured down the shuttle rathole, in addition to saving the cost of ISS support itself.