The Next Generation of Human Spaceflight

[Brian H]

Off the wall suggestion: eject cool gas along the leading edges to form a barrier, like bubbles around supersonic torpedoes!

[ladajo]

Ok, I'll call it a slightly guided mach 20 brick.

Oh, Netizen, you wrong the Shuttle! Everytime it had a chance, it landed on the runway!
Also, we would do well to remember the courage of John Young and Robert Crippen (the first).

Good thing there were several to choose from, and well (continentally) spaced on a "glide slope".

One question though, at what point does it start getting called a "gilde slope"?

I am a shuttle fan, but I limit my thinking to define flying as including the ability to go up. The shuttle on de-orbit is more like a lawn dart with wheels and a phobia of nose sticking.

[DeltaV]

...but why bother when you can use it for diamond cameral lenses all over a future spacecraft?

You are right, the cameras will never fail! Please see my earlier comment about passive safety.

Relying on cameras/electronics for external visuals is no more ballsy than what advanced modern aircraft already do: rely on electronics for flight control (and just about everything else). The pilot is only making suggestions to the computers. The computers vote and decide how far to move the control surfaces. He can switch off the computers, but then he loses protection from stalls, excessive sideslip, overstress, overspeed, windshear, etc. and has to baby the airplane much more.

Using redundant cameras/displays/power circuits with a proper geometric distribution for each camera group should suffice.

[DeltaV]

Off the wall suggestion: eject cool gas along the leading edges to form a barrier, like bubbles around supersonic torpedoes!

Easier to use skin electrodes or coils to deflect the plasma. (Around the cameras, not the entire vehicle. But with a Polywell available...)

[rjaypeters]

..Relying on cameras/electronics for external visuals is no more ballsy than what advanced modern aircraft already do: rely on electronics for flight control (and just about everything else)...

At last we are getting to the potentially overriding reasons not to go to the extreme trouble of arranging for transparencies.

Kelly Johnson bet his Skunk Works team ($100? real money back then) if anyone could find anything simple about the A-12 (SR-17, etc.). The bet was never collected.

Orbiting vehicles which reenter are worse in many respects than an A-12. Multiple cameras behind diamond apertures may be simpler, lighter, cheaper and safer than windows.

[GIThruster]

Windows are over-rated in lots of ways. Shuttle pilots don't actually look out the windows to land the skiff. They're positioned much too high in the cockpit to be useful for such:

http://www.chancebliss.com/wp-content/u ... ockpit.jpg

[rjaypeters]

Windows are over-rated in lots of ways. Shuttle pilots don't actually look out the windows to land the skiff. They're positioned much too high in the cockpit to be useful for such...

But downward-facing windows could be useful for landing. I'm just as happy with landing on instruments, but when the thread gets to cortical implants (even as a joke), I just want to add lightness and simplicate.

[GIThruster]

Well certainly the lightest visual accommodation is to use multiple redundant cameras and a head-mounted display for each crew member. If you absolutely want to have something like a window, then you can certainly put a single large screen in the front of the cockpit. they don't weigh so much and the feeling they would provide that you're looking through a window might justify the weight by virtue of improved psychological effects. Star Trek's craft have always had a common front and center view screen not just because of this, but because it makes good TV. A good view screen that's shared amongst the crew certainly removed ambiguity over what one another are seeing--handy when My Favorite Martian shows up. But don't you want to get him on camera?!

[93143]

That viewscreen and camera setup might be fairly complicated on its own, at least if you really want the crew to feel like they're looking out a window...

(I once read about a technology that could do something like the above, but additionally required a prohibitive amount of computational power. Perhaps it was superior in some other respect, but I can't find a reference...)

[DeltaV]

Some of the 3D TV technologies about to hit the market may be useful.

Other advantages of redundant camera-based "windows" for SSTO vehicles are increased tolerance to orbital debris impact and better structural load paths around the crew cabin.

On the military side, better protection against DEWs and blast radiation is a plus. EMP protection of the cameras, displays and their power circuits would have to be robust without real windows, but that would be the case anyway for other vehicle systems (e.g., reentry without the flight computers would be dicey at best, probably fatal).

[GIThruster]

Other advantages of redundant camera-based "windows" for SSTO vehicles are increased tolerance to orbital debris impact and better structural load paths around the crew cabin.

If you're going to use a wet filament wound composite body, the weight savings of no windows will be substantial as will the structural loading.

[GW Johnson]

I didn't say "don't do windows in re-entry", I said "be aware it is difficult and fraught with vulnerabilities that can lead to fatalities". Camera ports can have the same troubles. It's all in control of leak paths.

As I said earlier, the X-15 and the Shuttle used the same SiO2 quartz exposed to the environment. (Shuttle had two more layers inside.) Whether that was a cooled 3-layer assembly, I don't know, but I don't think it was. I also think SR-71 had quartz canopy panels like the X-15.

Transpiration cooling is a viable way to do it, but if the coolant pressure fails for any reason whatsoever, then the transpiration pores become pinhole leak paths, which quickly lead to failure. You could do a variation with external film cooling that flows up the windscreen as it boils away along the exposed surface, but the coverage is geometrically very "spotty", and once again the source ports become potential leak paths if coolant pressure fails.

Cooling between layers is probably a less-failure prone way to do it (in terms of leak path control), but there are very serious technical problems. If you use a liquid, you have problems with boiling as it rubs against quartz at 1000+F. Boiling kills the heat transfer apability in the vapor cloud region. If you use a gas coolant, you trade the phase change difficulty for far lower heat capacity and far smaller heat transfer coefficients generally. This can be designed-around, but it ain't easy.

What they did with Shuttle is the same as they did with Mercury, Gemini, and Apollo, all of which had quartz panel windows. You must be sure to face the window into a separated flow wake zone, not directly into the main flow. This drastically cuts the heat load to something you can survive within the material limits, which are more due to phase change than actual melting. This puts the onus on the flight controls to maintain attitude. If that's lost, you lose the window very quickly, followed by the crew.

The phase change thing with SiO2's like quartz unfortunately includes a volume change of about 2% or so. It occurs pretty close to 2200-2300 F, as compared to a 3200 F actual meltpoint. Either an isothermal chunk swells out of its mountings (and it is brittle, so this usually breaks it), or a nonisothermal chunk will crack at the interface between colder-than-critical and hotter-than-critical. It's a sudden volume change, it's irreversible (also killing transparency), and it's unavoidable. So, you just don't ever let it get that hot. (Also true of ceramic heat shield tiles - same SiO2 material, different form.)

I don't know, but I'd bet there's something similar lurking in the background with diamond or sapphire. It's something you have to test for in development. Once you know, you can specify what the worst-case conditions really are for the material. Someone might have already done that for diamond and sapphire, but I just dunno.

[GW Johnson]

How come this thread died? We had some good ideas going regarding visibility out of re-entry vehicles.

[93143]

I was going to try some design calculations for a pumped-water-cooled window, but I got sidetracked...

[rjaypeters]

How come this thread died?

If I don't have something to say, I don't.

Edit: The thread ain't dead, it's just resting!