Maybe with computers but 40 years ago scramjets and hypersonic flight were “any day now” and nuclear propelled missions to mars were just around the corner. Sound familiar? We’re also working on the “next generation” of heavy boosters that will incorporate J-2s from the Apollo era and has a load lifting capacity that anyone familiar with what they had in mind to follow the Saturn V with would laugh at. Or cry. That we aren’t further along than we are is a travesty.

With the computing power at hand now as you rightly say, and improving every year, it would seem likely that the path towards progress is much more clear currently. I believe most of the belligerent noises of “any day now” was more cold war propaganda than anything else. It would seem from press reports that NASA has internal problems…mostly management issues? and could this likely be stymieing creativity?

Fuel, money, and what people will accept are the three biggest obsticals. For traditional chemical rockets a tripropellant of hydrogen, oxygen, and fluorine seems to be about as good as you’re going to get as far as ISP is concerned. A strutjet would seem to be the best bet but nobody seems to be coughing up the dough to develope them. After traditional chemical rockets you get weird stuff like “hydrogen radicals”. If I remember correctly basically what that is is things like hydrogen and oxygen don’t float around as H’s and O’s but as H2’s and O2’s. When two seperate H’s combine to form an H2 it apparently give off some energy you can tap (last chemistry I had was ’bout 20 years ago so gimme a break ). Anyway the “theory” is they could get an ISP of about 2000. Don’t know if that’s taking radical H and radical O, making them into H2 and O2 and THEN making them into H20 (I think they either go fuel rich or oxygen rich but I don’t recall which).

Then you get stuff like “metastable helium” or “metastable hydrogen” whatever that is. I remember back in the 80’s there was an article in Airforce Magazine in which the talked about metastable helium and how they’d make it by “aligning the spin of the atoms with polarized lasers and stabilising it in a magnetic field”. Uh. . .okay.

The concept of fuel and the propulsion system as we know it now would have to be redefined to make such an aircraft a reality. Fuel and the propulsion system would be the biggest obstacles. The traditional chemical rocket fuels of now would provide the escape velocity but the quantity required for just a single flight is huge and these chemicals are highly volatile. The kind of propulsion system I am envisaging would likely have to transition smoothly from atmospheric flight to vacuum flight without loss of efficiency. Most probably such an A/C would likely use a different configuration of propulsion separately for atmospheric and space flight respectively?

I may be wrong but would you be referring to a hydrogen fuel cell. It is a great idea but I am unaware of any great progress in this field towards powering large machines. Perhaps progress is being made but kept hidden from the public eye?

After that you get various flavors of nuclear fission none of which the public wants anything to do with. And that’s a shame because it’s probably the best bet in the semi near term.

Fusion is WAY off. If/when they ever figure it out it will be the way of the future. I’m not sure if it’s a quesiton of money or not. If they were given $20 billion a year could they actually USE the money productivly? Is there enough work being done to use it that is?

Yes it is a shame that nuclear fission is not being harnessed towards this purpose because it is as you say probably the best bet in the short term. Radioactive contamination and atomic bombs have made fission unpopular and public sentiment towards fission as a result of Hiroshima, Nagasaki, Chernobyl etc. would definitely unseat any politician unwise enough to go against public opinion and sanction such a project. Purely from a scientific point of view, it is the best bet though and I am sure it can be very safely manipulated without any hazard whatsoever. Maybe a system that uses fission power in space flight alone with a different power source for atmospheric flight could solve the problem?

Fusion can very well be harnessed if a global effort is made and ITER Fusion Project is a step in the right direction. Given the resources that are being combined, a full-fledged fusion reactor in the next couple of decades is very much a possibility and though the safety hazards persist, it can definitely be harnessed for space flight.

Perhaps integrating scramjet engines and fission/fusion powered engines to alternately power atmospheric and space flight (fission/fusion reactors secured such that even in the event of a crash there would be no radioactive contamination) would be the way to go?

Regards