Will something like the Deltaglider ever be possible?

[MAPitard]

If so, how practical?

 

[pete.dakota]

Only as a third stage orbiter or re-entry vehicle. Unless some breakthrough allows mind-boggling fuel efficiency in the near future.

 

[YL3GDY]

It seems that it's possible, but not practical. When using chemical engines, you'll require a lot of fuel, so the vehicle must be much larger that DG, at least like Deltaglider EX.

There is a little known Russian hypersound plane project called Tu-2000. The second stage of this project is a one-stage winged launcher(max cargo mass - 10 tonnes), which is quite big - it's length will be about 70m! Note that it is using hydrogen as fuel and flying on scramjets while in atmosphere.

It's likely that reusable winged launchers is only tomorrow. The "Earth-space" cargo flow space is not so big. It's cheaper now to use ordinary launchers.

 

[kwan3217]

Thread Necromancy!

I was thinking about this a while back and I think there is a plausible way to do it with currently known physics, just not yet currently known engineering:

Polywell fusion - http://en.wikipedia.org/wiki/Polywell

I don't completely understand how this works, but it looks like a vehicle-portable fusion reactor. I imagine it in a jet engine. If you are in the atmosphere, you use the polywell to heat the air traveling through the engine, instead of burning kerosene to do it. Once out of the atmosphere, use an onboard supply of water or other convenient fluid. If it's water, you use some of the hydrogen as fusion fuel, some of the oxygen to breathe, and the rest for reaction mass.

With a fusion engine, you have plenty of power to accelerate the working fluid far faster than you can do by burning fuel, so it should be easy to get it up to 40km/s. Of course it will be REALLY hot, but this might be used to our advantage as well. If it is ionized, then use more electric/magnetic fields to keep it from touching the walls of the engine and accelerate it some more.

Look up Project Pluto for a design of a fission ramjet. Except for the radiation, my design is similar.

 

[ar81]

If you have fuel tank with subspace compression technology, it would work.
DG has an engine that is more powerful than space shuttle SSMEs and also it seems to have more fuel. Where is the big fuel tank of DG?

 

[Coolhand]

Thread Necromancy!

I was thinking about this a while back and I think there is a plausible way to do it with currently known physics, just not yet currently known engineering:

Polywell fusion - http://en.wikipedia.org/wiki/Polywell

Wow, i'd never heard of this before. :speakcool: Sounds like all the millions being invested in tokamak research - which isn't going to be achieving much for 40 or 50 years - should be invested in this instead.

 

[Andy44]

Assuming these theoretical power sources can be made to work, heat is indeed the real problem. A means must be found to make the reaction take place externally, within the nozzle bell itself instead of in front of it. I think the nuclear salt water rocket design aims to accomplish this, except with fission instead of fusion. Unfortunately it also means lots of radioactive fallout from the exhaust and an extremely delicate and dangerous fuel storage system. Plus the fuel itself is prohibitively expensive to make. Fusion that uses water as fuel and as propellant would be a wonderful way to get around these restrictions.

 

[Linguofreak]

The DG wouldn't be a really great design even if you had the technology to build it. Since it's a winged vessel, its best use would be as a surface to orbit shuttle on Earth, or any other planet with a substantial atmosphere. For any Earth-moon or interplanetary flight the wings are just dead weight, so such a mission would be left to purpose built craft without wings, streamlining, or landing gear. But the main engines are too overpowered and have too much fuel for surface-to-orbit operations (weight penalty), and the scrams probably aren't good enough to be worthwhile. The hovers are also impractical.

What you'd really want for such a craft would be this:

The main engines are obviously something nuclear, probably fusion, given the ISP of 40 km/s. If you can use that to provide the heat for the scrams, rather than the chemfuel they seem to use, then they don't actually need fuel beyond what's needed to power your fusion reactor (which comes out, I think, to a few grams/sec). Also, if you can build a fusion reactor/drive/scramjet, it's fairly likely that you can deal with temperatures high enough to operate the scrams up to a good fraction of orbital velocity. Once you get going the fastest you can with your scrams you can cut in the mains, which probably don't need a full 40 km/s of ISP, and certainly don't need the full thrust they have (they might be able to get by with a tenth or so of that). Another thing is that you wouldn't want to use the mains to accelerate you up to your scram ignition speed: you'd probably want some type of turbine or other low-speed engine, which could, like the scrams, be fusion heated rather than using chemfuel. Since the mains are now powering much less of the ascent, and since we aren't designing the thing to go beyond Earth orbit (geosynch is probably the highest we'll go), we can cut out a huge portion of the propellant reserve, freeing up space and weight for cargo.

 

[Andy44]

Nuclear fission-heated jet engines were experimented with during the Cold War and the DOD almost let a contract to build a nuclear-powered bomber which could stay airborne basically until the crew starved to death, but it never came to pass for a variety of reasons. The main drawback to nuclear-heated jets, ram, scram or turbine, is the shielding required to protect the crew and electronics from radiation. Fusion may indeed be easier to deal with.

I also agree that the DG is not a great interplanetary craft, not due to the wing mass, which can be used for fuel storage, but because of the lack of living space inside. A moon shot would be bearable, but going to Mars would not. The convenience of having wings is worth the extra fuel given the high tech near-fantasy drives we are using, since you are not dependant on another vessel for any phase of your flight.