If you boosted a business jet to 100,000 feet what happens? Can it come back down intact?

Even stupider than what was it, “Airport 75”(?) where a fully pressurized 747 sank into the ocean (without tearing apart or landing, without crumpling once submerged)? Never underestimate the ability of Hollywood to misunderstand how reality works.

There was a proposal many years ago, IIRC, to put a small rocket engine into the back end of a 747(?) and use that to boost it to a much higher altitude (60,000 ft? 75,000 ft?) where it would drop a small rocket; much like the underwing launch of the Pegasus - but the extra altitude and thinner air would give it more of a head-start.

As others point out, the typical passenger jet is not designed to work above about 50,000ft. The modifications needed would essentially make a new aircraft. Much bigger control surfaces, if not a attitude rocket system for control; possibly to be effective at thinner altitudes, the wing airfoil shape and even wing size might need updating. The current pressurization equipment would be inadequate due to thinner incoming air - would need bigger stronger pups; I don’t know if the current airliner designs tolerate a certain leakage and let the pumps keep up pressure, but if the seals are good, then presumably a short stint in the much tinner air would be doable.

Like the 747 example I cite, the problem too is speed. Unless we’re talking Concorde (in which case, build from scratch, use a B2 or something) the airframe and airfoil, nose shape, hull and wing strength, etc. are not designed for supersonic. Depending how you attach the rocket, the attach points have to be able to handle the stress of forcing the aircraft through the air until it gets to the thin air, much as the jet engine pylons do.

The iconic SR71 had a number of adaptions for travelling at 3,000mph - to allow the aircraft not to melt from friction, it was mostly corrugated titanium - corrugated to allow for expansion with the friction heat from Mach 5 at 80,000 feet.

All engines on board fail, and the aeroplane goes into emergency mode.

Running off battery.

Its going to be a real bitch to steer … but hang on, the air is so thin, the control surfaces don’t really work, its impossible, as it descends it runs into uneven atmosphere and strange effects, probably the nose would start to lift, and the back won’t get atmosphere as the nose blasted the air out of the way… So it goes nose up, and backflips… Sooner or later it flops down into the thick air at really high speeds, in a very awkward position, and the wings tear off …

I looked it up. It was '77.

Yes, stupider than Airport '77.

I know it would take massive modifications to make it work, my question was about what would the failure would be if you didn’t. The initial problem doesn’t say anything about speed. Assume we boost our bizjet to 100,000 but keep it subsonic while doing so; as it fell would it gain enough energy for heating to be a problem? As you descend and the atmosphere gets denser, would you have a chance to regain control or would aerodynamic forces tear the airframe apart first?

This whole plan reminds me of the pilots who were flying Pinnacle Airlines Flight 3701. Even without a rocket booster, it did not end well for them.

Do passenger jets lose cabin pressure as soon as they lose the engines? Can any one engine maintain cabin pressure, or is only one engine connected to the compressor?

I was wondering that. Aircraft-control issues aside, why would you need a special suit to stay alive?

Superficially similar, but that crew never actually lost control of the aircraft.

There is an altitude above which breathing even pure oxygen won’t sustain you because it’s just not at high enough pressure. This is the Armstrong limit, and it’s around 62,000 feet. If you’re above this altitude without a pressure suit (to enable you to develop an O2 partial-pressure in your lungs equal to or greater than the ambient pressure at 62,000 feet), you will die. Since engine power is required to maintain cabin pressure, having your business jet rocketed up to 100,000 feet without a pressure suit will be fatal.

Correction: I misremembered the Armstrong limit, which is the altitude/pressure at which water boils at body temperature. The pressure suit limit is more like 49,000 feet.

Debatable. Not to get too zen-swordsman-ish, but the chucklehead dudes would appear to have lost control early on.

Apparently, going up 15 km will reduce the air pressure by about a factor 10. So at 30 km it’s about 1% of sea level pressure and about 10% of what a business jet is designed for.

Not sure if that means you wouldn’t be able to point the plane forward. If that becomes a problem, then you’l end up in a spin and the question will be if you can get out of it when you descend into thicker air. That thicker air won’t hit you like brick wall, though, it gets thicker very gradually.

But before that the engines will very likely stop because they can’t get enough air in, which means the cabin pressure will bleed away and everyone will soon be unconscious and probably dead. The problem is not so much the boiling of bodily fluids, but that the partial pressure of even pure oxygen isn’t enough to have your red blood cells absorb enough of it. This effect kicks in at around 15 km. I don’t think regular airliners have facilities to keep the cabin pressure up when power fails, but because business jets fly a bit higher, maybe they do.

Wow - thanks. I assumed modern jet aircraft cockpits and passenger cabins are absolutely airtight and will hold in breathable air indefinitely. (Of course, I suppose it might get stale after awhile, or you might use up the breathable air and die of C02 poisoning). I had no idea engine power was, in fact, necessary to maintain cabin pressure.

Fascinating! Ignorance fought.

Are you sure that’s true though? I know under normal circumstances, air is constantly being pushed out the outflow vent (leaving disgusting cigarette tar stains on the side of the plane during the smoking era) but if cabin pressure starts to drop, the vent should close right? I imagine even with the vent closed the plane isn’t completely airtight, but it should hold for a while. Perhaps long enough to plummet from 100,000 feet to below the pressure suit altitude?

Just a note:

FAA requires pressurization or oxygen at 12,000 feet.

Unless your bizjet is made of plastic (and re-inforced with lots of titanium for the stresses of rocket flight), it is going to be out of air long before it drops 88,000 feet.

And, as noted, your blood will ‘boil’ without serious pressurization. And airplanes (which use ram air for pressurization) cannot pressurize without lots of air.

The X-15 had bottled gas for pressure and forced oxygen for breathing.

Airplanes don’t work much above 50,000 feet - Virgin Galactic’s White Knight launch plane drops the rocket-powered space plane at 50,000.

An airplane’s wing produces lift only when lots of air molecules are flowing over it. Around FL500, the molecules get few and far between.

What is so hard to imagine about this?

Yep, I was going to mention Yeager’s NF-104 flight also.

Not in the sense that’s relevant to this thread. Those two pilots tried to climb to the maximum their jet was capable of. While doing so, they exceeded other limits and damaged the engines. They still should have been within gliding range of an airport, but after diving to restart the engines and denying the severity of the problem to ATC they crashed a couple miles short of a runway.

Stupid, yes, but they never lost stability or steering control of the airplane.

My understanding is that cabin pressurization takes huge amounts of air not because the airplanes are super-leaky, but because the passengers would make the cabin completely disgusting if the air wasn’t constantly exchanging. The outflow vent closes immediately if the pressure drops because otherwise an unexpected engine shutdown would result in dangerously rapid decompression.

Considering that our hypothetical plane is going to drop the first 50,000 feet fast, it should be down to an altitude where the pilots can breathe only using an oxygen mask pretty darn quickly. Even if the plane is a little leaky when the vents are buttoned-up, it seems like it should be able to hold some pressure for the few minutes it takes to get there.

Pinnacle Airlines Flight 3701

This was simply tragic.

But it has nothing to do with the thin air above FL500 - the plane had a max operational altitude of FL410, and the airline had developed a secret “club” of pilots who had sneaked a plane to that level.

They did not run out of enough air to produce lift and operate control surfaces - they just exceeded the operational limits of the engines and failed to re-start the engines after they quit.
There was no indication that the cabin pressure was lost nor did the wing stall.

Both of which would have happened (real quickly) had they rocketed to 100,000’ MSL