Upper-Atmosphere Parachutes?

[Comet Tail]

So, here's something interesting I've come across...

Re-entering over Mars with a heavy craft is hard! (I'm using RO, here)

Ultimately, I've had to resort to opening massive drogue chutes at ~100 km, which fully deploy at a radar altitude of 70 km.

And... Well, it works beautifully. The craft never even encounters significant heating, and come down to 7 km, I'm going at a leisurely <200 m/s speed.

Now, I remember reading somewhere that if ribbon chutes open above about mach 1.3, that they start encountering some unwanted effects...

But I'm wondering, what kind of problems would I face if I tried doing this IRL? Why doesn't NASA just open a parachute in the upper atmosphere and descend without any significant heating? There's an altitude, there, where dragging effects are very much observable, but there's no significant heating. Open a parachute there, and it seems like it'd work very well. What's the catch?

[magnemoe]

Inflatable heat shields do much of this increase surface area to increase drag while having the heating apply to the huge surface to keep temperature manageable

An normal parachute would not work well as its not enough air to inflate it and the air behaves very different at pressure less than an millibar and hypersonic speeds.

[Moar Boosters]

The parachutes needed for mars are huge, so I'd imagine there would be significant g-shock to the spaceship if you managed to open it at near orbital speed. Maybe not enough to damage the spacecraft, but probably enough to tear the flimsy parachute apart.

[Ralathon]

You also have to take into consideration the mass of the chute. Big chutes means lots of mass. Something you don't want in spaceflight.

Also, if you have too much drag in the upper atmosphere you steepen your trajectory, making you hit the lower layers of the atmosphere with faster speeds and thus increasing the G load and making your landing zone less accurate.

[Shania_L]

Big heat shields are also heavy. I suppose the difference comes from entering Martian atmosphere from a direct entry interplanetry speed, and from a Mars orbit. I believe most if not all Martian landers IRL are direct entry so do not spend a significant amount of time in thin upper atmosphere.

You have the tradeoff between a potentially lighter parachute based aerobreaker, but with the added mass and complexity of having to perform a capture to orbit then a (Re-)Entry. Or just going for a KISS and fire your probe at the big red bit and accept that you are going to have to pack a big heavy heatshield onto it.

[IronGremlin]

http://www.nasa.gov/jpl/ldsd/pia18424/

NASA is developing this technology currently. There are some engineering challenges to overcome in the construction of the chute, but this is possible.

It's not really a cure all by any means, but it's a valid methodology. I'm not 100% sure why this hasn't been attempted on previous mars missions, but I suspect that intended delivery mass is a factor - the less you weigh, the easier it is to enter the atmosphere, so it may have just been that it was easier to engineer an effective lightweight heat shield than a parachute for the relatively light payloads we've sent to the surface so far.