MARS - How do parachutes even work?

a reply to: KaDeCo

Stop typing hoax into the search bar on youtube and you won't find dumb videos.

3 of those were used to slow the Mars lander, please note the size of the human there.


this is what slows a human down on earth, again please note the size of the human there.


Idiocracy is becoming a documentary in real time.

a reply to: Zaphod58

Rocket rockets rockets!

If a gas exist.. yeah.. fibers will catch it...

Hey.

Vector99

Only one (1) large chute was used to aid in the deceleration of Curiosity. Note the size of the human. With 100x (1%) the atmosphere the parachute would have to be 100 x larger. For the human. So they didn't splat. You can't even deploy in low atmosphere thus the question. But the explanation I found, with the help of the moderator and the documentation here: www.ssdl.gatech.edu... was sufficient. The parachutes DON'T actually work on Mars, but slow down the craft enough to not strain the heat shielding, and allow the secondary options to actually function.

There's really no reason to be a jerk when someone has a genuine question.

Nice pictures though.

Mars has 38% the gravity of Earth

You answered your own question in the OP . At that gravitational pull , any atmospheric resistance would enable a chute to work

a reply to: KaDeCo

You are right, I was mistaken on the amount of parachutes. Not sure why I thought 3 but I did.

On that note regarding the entry and descent, you need to also calculate the following factors

*Atmospheric pressure at altitude
*Angle of entry
*Atmospheric pressure at deployment

I do apologize for the smart-ass response, but seriously, do you think we didn't land on Mars?

Here is the NASA link regarding it

a reply to: Vector99

Three chutes were used in the Apollo missions for the re-entry.

No I genuinely wanted to know how the parachutes even worked, I know on Earth they can't even deploy at certain altitudes because there's so little atmosphere. I was thinking if they auto-deployed how could they be so small compared to how much they would need to produce for drag, even at 38% of gravity. The weight / cost / size associated with such a device baffled me. How would they even inflate if they needed to be that much bigger? I was under the wrong assumption they had a lot more involvement on the descent aspect of the landing than they actually do.

Now my brain is wondering (though I know we can't ACTUALLY descend to Jupiter and 'land' but if we COULD) how in the world would that work? You'd have a ton of atmosphere to use for drag but a ton of gravity to fight.

These are the things that keep me up at night.

Parachutes used on Mars weren't used to slow the craft to a gentle touchdown like you seem to assume they should've.

The craft was entering the atmosphere at very high speed, even causing the reentry heat. The parachute was very large, and had enough of the incoming air to open and do its work, as intended. Rockets and a sky crane were used for the actual gentle landing, as has already been mentioned.

Speed is the key. The shooting stars you see in the night sky are created by sand grain-sized meteoroids that burn up at the altitudes of around 60 to 100 km, which for us is practically vacuum of space. Yet for them, it's like hitting water at 100 miles per hour.

Here's a video created from the images taken during the landing of Curiosity rover, it plays out in real-time:


www.youtube.com...

Even with the parachute open and providing some drag, the craft was practically plummeting down.

a reply to: Urantia1111

I'm interested in where you grabbed the '3%' figure?

a reply to: KaDeCo

Just an idea:

If you used a material sufficiently heat resistant, you could deploy a parachute in the even the vacuum of space by incorporating a self-inflation system compose of sealed tubular ribs inflated by a self-contained gas.

Kind of like an umbrella were the ribs are inflate tubes instead of metal spars.

originally posted by: Bhadhidar
a reply to: KaDeCo

Just an idea:

If you used a material sufficiently heat resistant, you could deploy a parachute in the even the vacuum of space by incorporating a self-inflation system compose of sealed tubular ribs inflated by a self-contained gas.

Kind of like an umbrella were the ribs are inflate tubes instead of metal spars.

NASA tested something similar - an inflatable heatshield:


www.youtube.com...

I know a guy who is deeply involved with the topic. When I first met him (35 years ago?) he was designing hang gliders.

He's actually kind of a jerk. But brilliant.

originally posted by: Urantia1111
a reply to: Chadwickus

I am interested, hence the inquiry.

So live astronauts are going to go bouncing along the surface of Mars on airbags and they'll be ok with that?

Won't that be particularly damaging to their bodies weakened by months in space?

To my knowledge live astronauts have not landed on Mars. So why would how they land probes matter for live astronauts?

originally posted by: KaDeCo
With 100x (1%) the atmosphere the parachute would have to be 100 x larger.

False.

The velocity of the parachute's descent doesn't vary linearly with the atmospheric density, so with 1% of the atmosphere you don't need 100x the parachute as that would assume it's a linear relationship. It's not linear, here's the non-linear formula, where rho is atmospheric density (slightly edited as original format won't display properly on ATS):
Calculating the descent rate of a round parachute

For most of its trajectory, the descent speed (velocity or V) of a round parachute has a near-constant value which can be computed from:

V = SQRT((2W)/(rho C S))

CD = parachute drag coefficient which is approx 0.75 for a parachute
without holes or slits cut in the fabric
rho = air density
W = weight of the parachute + load, in pounds (English) or Newtons (Metric)
V = vertical descent velocity, here expressed in ft/sec (English) or m/sec (Metric)

The parachutes DON'T actually work on Mars, but slow down the craft enough to not strain the heat shielding, and allow the secondary options to actually function.

The parachutes do actually work on Mars, not as well as on Earth but it doesn't make sense to say they don't work. The rockets in the video wildespace posted obviously do a lot of the work so you're right that the other methods of slowing the descent are important.

a reply to: Arbitrageur


Add that the amount of drag is proportional to the square of the velocity and the 'chute starts to look somewhat more effective (just doubling the velocity results in 4 times the drag)

originally posted by: Pilgrum
a reply to: Arbitrageur

Add that the amount of drag is proportional to the square of the velocity and the 'chute starts to look somewhat more effective (just doubling the velocity results in 4 times the drag)

Also considering just the volume of air captured by the chute, the volume would increase roughly 8X for every doubling of the chute diameter. When talking volume, it is a cubic function. Therefore (being a cubic function), a chute that is only 4X larger in diameter would hold roughly 64X more volume of air.

I say "roughly" because this calculation assumes the chute is a perfect hemisphere, which may not be the case for whatever chute they will use on Mars.

originally posted by: Pilgrum
Add that the amount of drag is proportional to the square of the velocity and the 'chute starts to look somewhat more effective (just doubling the velocity results in 4 times the drag)

That's true, it's actually in the formula for descent velocity, so the same parachute on Mars should have a descent velocity different by the factor of the square root of 100 (since Earth's atmosphere is about 100 times more dense), meaning it's only 10 times faster with 1% of the atmosphere, and indeed wildespace's posted video shows the descent rates on Mars can be quite fast, though probably not 10x faster because the chutes tend to be larger.

a reply to: Box of Rain
True, but the volume of air isn't one of the factors in the descent velocity formula I cited, the "S" is the surface area of the chute which is still a square rather than cubic function.

originally posted by: Urantia1111
a reply to: Chadwickus

I am interested, hence the inquiry.

So live astronauts are going to go bouncing along the surface of Mars on airbags and they'll be ok with that?

Won't that be particularly damaging to their bodies weakened by months in space?

Why bother reading previous posts etc when you can make assumptions & jump to conclusions a lot like the people who gave your post stars

Aerobraking--using atmospheric friction to slow a spacecraft.

Parachutes.

Retrorockets.

In any combination will work sufficiently well to slow a craft enough to safely land.

The methods to do so are well understood, the trick is to modify it to the point it'll work. That's a matter of practice, and experimentation.