Indeed. Landing on the Moon required the Lunar Module to carry roughly 18,000 lbs (8,200 kg) of fuel in its descent stage. You could replace all of this fuel with an aerodynamic fairing (not sure if you need a heat shield since the initial descent speed isn't that high) if the Moon had a substantial atmosphere. This fairing would have a fraction of the mass of all that fuel.Using the braking of the atmosphere is really good value (weight for weight, compared with fuel).
Who'd want to test pilot such a re-entry system? Several 'déja vue' situations in a row and each one just as likely to involve frying.FWIW, I don't think any crewed craft have used this (Per '2010' ?), only some space probes doing Mars' atmospheric braking to save fuel...
You don't solve any problems if you just use fuel to try to avoid the heating. That way is a straight trade off of fuel against heating penalty as far as I can see.Also keep in mind that the earlier you try to decelerate to avoid the heat, the longer gravity pulls you and thus the more fuel you need to constantly stay below the velocity needed to avoid the heat.
Perhaps not "without using fuel" but with some intelligent refrigeration system. The temperature difference between the surface of a 'hot' craft and the effective temperature of surrounding space is actually quite large so the performance coefficient could be pretty good.dissipate it as effectively as possible without using fuel.
Aerobreaking for orbiters (for the few cases it has been employed) only dip into the top of the atmosphere to reduce mechanical and thermal loads. As far as I know aero-capture (i.e. dropping from hyperbolic to elliptical speeds via aerodynamic drag alone - a more intense form of aero-breaking) has not been performed in practice yet.Downside, your heat-shield & structure must tolerate such 'short cycling', must not 'soak' cumulative heat and, yes, must dissipate one dip's heat before starting the next...
FWIW, I don't think any crewed craft have used this (Per '2010' ?), only some space probes doing Mars' atmospheric braking to save fuel...
The front is really hot, the side is still very hot, and the back is a vacuum where you only have radiation. Dumping the heat into stuff inside the spacecraft is the only reasonable option for things that need cooling.Perhaps not "without using fuel" but with some intelligent refrigeration system. The temperature difference between the surface of a 'hot' craft and the effective temperature of surrounding space is actually quite large so the performance coefficient could be pretty good.
Zond 6 and 7 made a full orbit after slowing in the atmosphere.
Didn't knew about those probes, thanks.Zond 6 and 7 made a full orbit after slowing in the atmosphere.
I wouldn't argue with that but refrigeration systems do not rely on external convection to shed heat in principle. I did use the term "intelligent refrigeration" and that would need to involve a very hot heat sink. Obvs a liquid based refrigeration cycle wouldn't work.The front is really hot, the side is still very hot, and the back is a vacuum where you only have radiation.
The shuttle had (by design) a pretty low L/D around 1 (between 1 and 2 orders of magnitude lower than normal airplanes) which combined with the fact that it is unpowered gave it a fairly steep approach that for most regular pilots would likely be more comparable to controlled falling than level flying. I think its fair to say that most regular pilots probably would not be able to successfully land the shuttle manually without some study and training firstEveryone always says it flies like a brick
I don't find the orbit description any more that I read a while ago but you can check e.g. Beyond Earth. Page 81 describes the Zond 6 re-entry, the first skip reduced the velocity to 7.6 km/s, that is the velocity of a low Earth orbit. With a eccentricity that gives you nearly a full revolution before you enter the atmosphere again. You could call it a very long skip.Didn't knew about those probes, thanks.
You mention they did a full orbit after aero-breaking, so I assume the probes did a "simple" ballistic aero-capture followed by reentry at next perigee? The wikipedia article mentions they employed skip-entry, but as I understand skip-entry that is a maneuver for sub-orbital speeds where lift is used to turn the trajectory upwards to extend the range.
You are not in orbit in the situation considered here.In fact, if the orbit were elliptical
Well, Google tells me the shuttle has an L/D max (glide ratio) of 4.5 on approach, but a 747 is 15. A Cessna 172 is 9. Sure, the method is the same - pitch for the glide airspeed - but it's a lot steeper.Yep. Shuttle was the result of the lifting body tests combined with the X15.
But her gliding is on par with a 747.
Just keep her at <370KIAS and she flies well enough