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Curiosity is about a week off landing





Josso
I think it's August 6th @ 5:15 UTC.

If I remember correctly it's an epic undertaking. They have to fire a parachute at a certain altitude, cut that off, fire thrusters and hover it close to the ground, lower down the rover gently and then cut those cords and then veer the thruster module off the the right to make sure it doesn't hit the rover.

Truely awesome. All done by clever programming as by the time they get the signal it's hit the atmo it's already down (or crashed!).

I'd be watching NASA TV if you can they should be some good coverage (not sure what they are doing for it but should be interesting). You can get it on ustream in HD somewhere if you search.
ocalhoun
Josso wrote:

If I remember correctly it's an epic undertaking. They have to fire a parachute at a certain altitude, cut that off, fire thrusters and hover it close to the ground, lower down the rover gently and then cut those cords and then veer the thruster module off the the right to make sure it doesn't hit the rover.


Is it just me, or does this seem unnecessarily complicated?

Wouldn't it be easier to first land the thruster module, have it right itself*, then have the rover unload?

*(easy enough, given a well-planned overall shape and weight distribution; it would only take a few hydraulic rods pushing out to make sure the correct side was up)


And I suppose they're jettisoning the parachute and moving to thrusters in order to make sure it doesn't get tangled in the works after landing? I guess that makes sense... it just seems like there must be a simpler, more elegant solution for that...
Hm... I wonder if they'll ever make a lander designed to make space shuttle-style landings, gliding in, taking lots of close-up pictures along the approach, then finally going in for a vertical landing once enough speed had been bled off...
Come to think of it, that would be particularly useful if the rover could be loaded back into the lander and it could take off again, moving to a new location to explore... while it would require a substantial amount more weight, it would allow them to explore a much wider and more varied area... probably worthwhile, since it would allow one mission to explore as much as several separate missions would have been able to.
playfungames
Indeed, the rover has now landed. I have seen pictures of it everywhere on the internet. They have fired stuffs from it blowing up something on mars I think. I hope they have plans to land on other planets and moons as well. Who knows, we might find basic life even within the solar system. I hope they do it within my lifetimes because I want to see how it goes. But those things take a lot of time Sad. Reaching the closes planet itself is such a long time for us humans.
ocalhoun
playfungames wrote:
Reaching the closes planet itself is such a long time for us humans.

Depends on the timescale you're using.

Less than 50 years to go from the moon to Mars isn't bad... not when viewed over humanity's 10,000-20,000 year existence...
Josso
ocalhoun wrote:
Is it just me, or does this seem unnecessarily complicated?


Didn't see this before: yes! it does but if I remember correctly it was something to do with slowing the thing down fast enough. It's the biggest rover ever built, the payload plus craft was pretty heavy.
ocalhoun
Josso wrote:
it was something to do with slowing the thing down fast enough. It's the biggest rover ever built, the payload plus craft was pretty heavy.

...Still, so you just give it a bigger parachute.

I mean there must be some reason they made the landing sequence so complicated... but just 'it was big' doesn't justify the extra complexity...
kelseymh
ocalhoun wrote:
Josso wrote:
it was something to do with slowing the thing down fast enough. It's the biggest rover ever built, the payload plus craft was pretty heavy.

...Still, so you just give it a bigger parachute.

I mean there must be some reason they made the landing sequence so complicated... but just 'it was big' doesn't justify the extra complexity...


The discussion that I read on the JPL Web site was that the payload was far too heavy (read, "has too much inertia") to slow down for a soft landing in one step.

The supersonic parachute used was already the largest deployed so far; essentially, it was the largest they could test and confirm would actually function correctly. After that deceleration, the craft would be too big, and going too fast, to make use of the "airbag" landing used by the rovers. So a thruster-based descent was required.

At that point, do you attach the thrusters, and all of the associated hardware, permanently to the rover? That makes the rover itself even larger, heavier, and with more stuff on it in place of science apparatus. Instead, you separate the thruster/descent system from the rover proper. One option would be an Apollo-style lander with ramps, where the rover drives off after touchdown. The problem with that is the lander has to be level, or it will topple over (or dump the lander off). Not good.

The rover itself is already designed with a suspension system to handle fairly steep slopes, large rocks, etc. So use it. Make the descent such that the rover itself is what hits the ground first. Then it doesn't matter much if it lands on a rock -- it's designed to handle that.

How do you get the rover below the the thruster unit, and keep the latter from hitting on top of the rover? Hence the skycrane and post-descent sideways burn.
ocalhoun
kelseymh wrote:
ocalhoun wrote:
Josso wrote:
it was something to do with slowing the thing down fast enough. It's the biggest rover ever built, the payload plus craft was pretty heavy.

...Still, so you just give it a bigger parachute.

I mean there must be some reason they made the landing sequence so complicated... but just 'it was big' doesn't justify the extra complexity...


The discussion that I read on the JPL Web site was that the payload was far too heavy (read, "has too much inertia") to slow down for a soft landing in one step.

The supersonic parachute used was already the largest deployed so far; essentially, it was the largest they could test and confirm would actually function correctly. After that deceleration, the craft would be too big, and going too fast, to make use of the "airbag" landing used by the rovers. So a thruster-based descent was required.

At that point, do you attach the thrusters, and all of the associated hardware, permanently to the rover? That makes the rover itself even larger, heavier, and with more stuff on it in place of science apparatus. Instead, you separate the thruster/descent system from the rover proper. One option would be an Apollo-style lander with ramps, where the rover drives off after touchdown. The problem with that is the lander has to be level, or it will topple over (or dump the lander off). Not good.

The rover itself is already designed with a suspension system to handle fairly steep slopes, large rocks, etc. So use it. Make the descent such that the rover itself is what hits the ground first. Then it doesn't matter much if it lands on a rock -- it's designed to handle that.

How do you get the rover below the the thruster unit, and keep the latter from hitting on top of the rover? Hence the skycrane and post-descent sideways burn.

Ah, finally a good explanation!
It still seems like it should be possible to simplify it at least a little*, but now it at least makes sense why they did all that.

*I'd be tempted to investigate a space shuttle style gliding vehicle that drops the rover on a parachute (like a military cargo plane making an airdrop) once it loses enough speed and altitude... then goes on to make a crash landing.
Pro: you could put cameras/instruments on it and get close-up pictures of a wide section of the Martian surface as it glided down.
Con: maybe the Martian atmosphere is too thin for that to work well, making a glider design necessarily too big and heavy in order to have a sufficient wingspan.
Pro: you could design a single larger entry vehicle that drops multiple rovers over a widespread area relatively easily. (That way only needing to do the hard work of descending through the atmosphere and slowing down once instead of two or three times. Each rover could be of the same design, just perhaps with different instruments, saving on development costs.)
Con: It would need heat resistant coating over a much larger surface, perhaps making it too heavy (though, in exchange, you wouldn't need much, if any, thruster fuel.)
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