Parachute Problems Plague NASA's Flying Saucer 41
An anonymous reader writes: NASA's test of a Mars landing system came to a end Monday when the saucer-shaped vehicle's parachute tore away after partly unfurling high over the Pacific Ocean. NASA says they will provide more details at a news conference Tuesday. Another parachute failed during a similar test of a new Mars spacecraft last year. "This is exactly why we do tests like this," NASA engineer and LDSD mission commentator Dan Coatta said after the test. "When we're actually ready to send spacecraft to Mars, we know that they are going to work when that big mission is on the line."
I know a lot of this is cutting edge... (Score:3)
... but the parachute? Really? If you know the speed and the density of the atmosphere you're going to deploy it in then the rest is basic physics and engineering. Just make sure you make the damn thing strong enough!
Re: (Score:1)
Re: (Score:2)
Re: (Score:2)
It's not the first time they've had problems with chutes either, however this is the biggest one they've done so far, and things don't always scale up (you need thicker fabric, etc to handle larger stresses)
From the limited video footage, the chute looked to be already torn at deployment, so it may have been doomed to fail well before it opened (though NASA have had tearing problems before, one wonders if they had built anything in to mitigate that known risk into the design)
(*i am not an expert, just an average thickie)
The parent is right. A supersonic parachute deployment will require modeling the fluid (air) and the chute's structural mechanical response in a coupled fashion. This would push current computational limits. The fact that they modeling materials whose dynamic response is poorly studied (fabric) makes it all that much harder from an engineering perspective.
Realistically, some computational modeling might get you in the right ballpark, depending on the quality of the modeler and model, but you're going to
Re: (Score:2)
a lot of parachute issues are deployment problems at speed/ heat.
Take a spacecraft which is flying at thousands of MPH toward the ground, burning at 2000 degrees, and then deploy a soft fabric.
If you don't unfold it perfectly you lose everything. if one strand of folding rope is out of place you lose everything. The amount of engineering going into just the folding of a parachute would surprise you.
Re: (Score:2)
a lot of parachute issues are deployment problems at speed/ heat.
Take a spacecraft which is flying at thousands of MPH toward the ground, burning at 2000 degrees, and then deploy a soft fabric.
If you don't unfold it perfectly you lose everything. if one strand of folding rope is out of place you lose everything. The amount of engineering going into just the folding of a parachute would surprise you.
Yeah, about this...
Why is it so hard to develop a control unit to unfold the parachute? I know it's been used thousand time with success already but is there no other way than blowing up the cover and throwing that big ball of parachute and hoping it will unfold perfectly? (Yes, I know it's more controlled than that, but you get my point)
Re: (Score:1)
Re:I know a lot of this is cutting edge... (Score:4, Interesting)
Parachutes don't just unfold, they actually deploy in a very controlled fashion. All it takes is something to initiate the sequence. In human parachutes, a pilot chute is released, which pulls out a deployment bag. The bag in turn does not open until suspension lines are stretched, and once the canopy is released from the bag, it inflates due to the difference in static air pressure within. vs dynamic air pressure outside (Bernoulli's principle [wikipedia.org]). There are further mechanisms to slow down deployment in order to control the deceleration and opening shock (important for human well being). Problems occur if things happen out of sequence, or if the parachute is structurally unsound.
I can't speak for the system NASA is using, but I expect there already is a unit to "unfold" the parachute, and it is all part of the parachute system already.
Re: (Score:2)
The idea is to make such a parachute optimal for the device it wants to land. To bulky it become more expensive to deploy, as well unlike earth Mars has a thinner atmosphere so it will need more surface area. So the engineering spec would to make it bigger and smaller at the same time.
Re:I know a lot of this is cutting edge... (Score:5, Informative)
... but the parachute? Really? If you know the speed and the density of the atmosphere you're going to deploy it in then the rest is basic physics and engineering. Just make sure you make the damn thing strong enough!
You would think so, yes, except that no one has developed a parachute precisely (or even remotely) like this one before: it's the biggest super-sonic parachute ever (the ring portion of the 'chute deploys at over Mach 4 ... normal aerodynamics don't work there), AND, it has to be light enough to meet mission parameters for weight budget. While you might think it's basic physics, the empirical details are a bear to get right.
It's not just that this is, in fact, rocket science, but really, really hard, cutting-edge rocket science.
Having watched the NASA-released video, the failure mode appeared to be very different from the first test. The first test suffered from imperfect deployment that resulted in uneven loading and thus failure of the main 'chute. The droge (the first little 'chute) went out perfectly, but the main parasol failed to open. The second test failed more quickly, without even partial deployment of the main 'chute, as if it was immediately ripped apart. Watch the videos, they're fascinating!
Re: (Score:1)
Having watched the NASA-released video, the failure mode appeared to be very different from the first test. The first test suffered from imperfect deployment that resulted in uneven loading and thus failure of the main 'chute. The droge (the first little 'chute) went out perfectly, but the main parasol failed to open. The second test failed more quickly, without even partial deployment of the main 'chute, as if it was immediately ripped apart. Watch the videos, they're fascinating!
2014 high-res video (around 1:20):
https://www.youtube.com/watch?... [youtube.com]
2015, low-res video (around 4:00):
https://www.youtube.com/watch?... [youtube.com]
I don't know how you can see much from the second video, as NASA has not released anything high-res yet.
could be the same problem as before, the feed is way too low-res to understand what went wrong.
Re: (Score:3)
I don't know how you can see much from the second video, as NASA has not released anything high-res yet.
could be the same problem as before, the feed is way too low-res to understand what went wrong.
Thanks for the links. I had another look and you may be right -- it may be the same failure mode. In fact, it might be that the most recent 'chute actually lasted longer than the first one.
Re: (Score:2)
Huh? The GP said the exact opposite.
Re: (Score:2)
It's not a parachute in the classic sense - it's more like an enormous airbag around the perimeter of the craft designed to help high-altitude aerobraking. Lots of problems to solve.
The SIAD or "airbag" has worked flawlessly the last two tests. The parachutes are the systems that have been failing... 0 for 2. If the 3rd test produces the same result with the chute then maybe the team should switch focus and bump up the specs on the SIAD and concentrate on retro rocket landings.
Re: (Score:2)
The weight of the motors and fuel has to be subtracted from you payload. The cost in weight for parachutes is much less.
Re: (Score:3)
... If you know the speed and the density of the atmosphere you're going to deploy it in ...
Nontrivial. Requires the ability to forecast high altitude Martian weather years in advance. So far, we can barely manage a few days in advance for Earth weather. Then there's that minor detail of wanting some flexibility to adjust the atmospheric attack angle in case the arrival date isn't quite what was originally intended. No it isn't rocket science. It's way harder.
Re: (Score:2)
Oh, I don't know ... solving specific engineering for a specific task is always going to involve new stuff.
I'm sure this is way more complicated than "basi
Re: (Score:2)
... but the parachute? Really? If you know the speed and the density of the atmosphere you're going to deploy it in then the rest is basic physics and engineering. Just make sure you make the damn thing strong enough!
Ya, but in theory, theory and practice are the same, but in practice, they are not.
Still better than when... (Score:2)
Not for long... (Score:3)
>> Parachute problems plague flying saucer
Not for long. The ground problem soon became a bigger issue.
The important part (Score:2)
vueja de (Score:3)
Video (Score:5, Informative)
https://www.youtube.com/watch?... [youtube.com]
You can see the parachute deployment and tear-down at 5:40
how many successful deployments needed? (Score:1)
Because if you're sending an extremely expensive rover to another planet and depending on this thing, I think you don't want to fail several times, finally tweak enough to achieve one success, and say, "done!".
Was that one success just a fluke? One chance in 20 where everything went just so? I think you'd want a higher confidence answer than that.
LDSD (Score:2)
I once saw a flying saucer on a parachute after taking some LDSD, so getting a kick out of this...
Plague? Is this the Daily Mail? (Score:2)
Two data points does not a plague make.
Seen this before (Score:1)
Seems the Roswell aliens had the same problem. [alien-ufo-research.com]