Is is possible that we can send up a large jet, which will carry It’s own oxygen so It can become a rocket (at the right altitude) to send it into orbit? I understand re-entry might be a problem , but maybe this could be a new approach?
In my opinoin something new-different needs to be done to advance the NASA program.
My understanding is that the major problems with this idea are that the planes can’t carry enough fuel to get them to orbit. Obviously there’s a lot of work that needs to be done with both what fuels are used and what materials go into the planes.
And for those of us still awaiting the magical process to not only produce Mkg of nanotubes but the funky loom to weave them together … (Sorry Cillasi it is meant as a gentle dig)
Here’s a proposal for an in-flight refueling space plane
Cillasi, do we have the technology to do this?
Grey, thanks. That was what I was looking for. Seems there is the possibility of orbiting with in-flight refueling. A very informative article.
Those guys know their stuff.
Conventional jet engines only go up to Mach 6 or so. You need about Mach 24 to get into orbit, and for that you need a scramjet engine (supersonic combustion ramjet engine). NASA will soon be testing the X-43 to test this technology, but it’s a long way from being used on a manned spacecraft.
I’m going to seriously butcher this, but my understanding is at this point sending something straight up is the most efficient way to go. I pray more a more informed Doper will come along and expand on that.
Jake, what you are envisioning sounds a lot like the old X-plane program. It was a little different in that the rocket plane piggy-backed on a jet, but there still was no vertical takeoff involved and all components were completely reusable.
True, straight up is the fastest way to get out of the atmosphere, so that the reduced air pressure will make your engines more efficient.
But once you get up there, then what are you going to do? You’re gonna start falling unless you can start moving sideways at 18000 mph. Making a sudden turn from “up” to “east” is not terribly efficient.
That’s why they gradually level out, making a nice smooth arc from straight up at the launch pad, to horizontal at orbital insertion. They even have cool computers to figure out how sharply to make those turns.
I’m no rocket scientist but why are aerospike engines not used on current rockets? I was under the impression that they were more effective then bell nozzles.
Well, the idea of carrying both fuel and oxygen-source in a flying vehicle, rather than depending on the oxygen in the atmosphere, is not a new one; it’s been around since before WWII. However, the technical term for a vehicle that carries both fuel and oxidizer and combusts them to produce thrust is one you might have run into: it’s rocket.
Because it’s a new technology, and there are no new rockets. It’ll be a while yet before all the bugs are worked out, but eventually, yes, you proabably will be seeing them on spacecraft.
Um, no. You can get to orbit creeping along as slowly as you want, as long as you keep applying thrust. I’m not sure where you got Mach 24. That’s somewhat less than escape velocity at STP, but you certainly don’t have to go even that fast to get to orbit.
It’s pretty hard to get to orbit with a jet engine, scram-jet or otherwise because you run out of thrust when you run out of atmosphere. There have been some proposals that use ballistic trajectories - accelerating in the atmosphere, coasting a distance at an altitude too high for the scram-jet to work effectively, and then descending for another thrust phase. There are also some plans to convert the scram-jets to rockets when necessary, but this requires on-the-fly structural modification, not just injection of an oxidizer.
Clarification on previous - when you get to “orbit” you obviously have to assume an orbital velocity consistent with your altitude in order to stay there without additional thrust, so I don’t mean my comments to imply that you can insert yourself in orbit very slowly. At these altitudes, you typically express orbital velocities as a speed rather than a Mach number because Mach is fairly meaningless at the densities encountered there. My post above was simply pointing out that you can get to that altitude with no requirement on the speed required.