Author Topic: Skycrane: Way to go or one off experiment  (Read 13008 times)

Offline tj

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Re: Skycrane: Way to go or one off experiment
« Reply #20 on: 08/07/2012 04:51 am »
Here are some JPL design trades on the use of the sky crane.

6/28/2010. The MSL SkyCrane Landing. Architecture. A GN&C Perspective. Miguel San Martin. Jet Propulsion Laboratory, California Institute of Technology .

www.planetaryprobe.eu/IPPW7/proceedings/.../Session5/pr478.pdf

6.4MB file

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Offline kkattula

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Re: Skycrane: Way to go or one off experiment
« Reply #21 on: 08/07/2012 05:01 am »
I can't see why this wouldn't scale up to larger payloads. AIUI, the scale issues would tend to be more about entry shield diameter, and parachute size.

Bigger engines, more fuel and stonger cables, are minor engineering issues, once you've cracked the basic problem.

For habitats, (and other cargo), for a manned mission, it would still be handy for the landing gear to have wheels.  Even if the payload isn't a self-powered rover, it could still be towed to a convenient location, in a surface rendezvous scenario.

This means everything doesn't have to be landed in one or two large payloads. Several smaller ones can be pre-deployed and gathered together. Landing 1 ton at a time might be a bit small, but 5 to 10 tons, looks reasonable.
« Last Edit: 08/07/2012 05:01 am by kkattula »

Offline kkattula

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Re: Skycrane: Way to go or one off experiment
« Reply #22 on: 08/07/2012 05:05 am »
Here are some JPL design trades on the use of the sky crane.

6/28/2010. The MSL SkyCrane Landing. Architecture. A GN&C Perspective. Miguel San Martin. Jet Propulsion Laboratory, California Institute of Technology .

www.planetaryprobe.eu/IPPW7/proceedings/.../Session5/pr478.pdf

6.4MB file

Source: public web


Link doesn't work, try: http://www.planetaryprobe.eu/IPPW7/proceedings/IPPW7%20Proceedings/Presentations/Session5/pr478.pdf

Offline spectre9

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Re: Skycrane: Way to go or one off experiment
« Reply #23 on: 08/07/2012 05:08 am »
I do wonder if more than 1 of these parachutes can be used at once now it's been tested on Mars.

Good tech should be used again.  :)

Offline tj

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Re: Skycrane: Way to go or one off experiment
« Reply #24 on: 08/07/2012 05:20 am »
37 Tons to Mars

High Mass Mars Entry, Descent, and Landing Architecture Assessment
http://www.ssdl.gatech.edu/papers/conferencePapers/AIAA-2009-6684.pdf

PublicWeb

Offline alexterrell

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Re: Skycrane: Way to go or one off experiment
« Reply #25 on: 08/09/2012 11:12 am »
37 Tons to Mars

High Mass Mars Entry, Descent, and Landing Architecture Assessment
http://www.ssdl.gatech.edu/papers/conferencePapers/AIAA-2009-6684.pdf

PublicWeb
This paper shows the entry and descent requirements for a 37 ton payload, but not the best landing technique.

Would a skycrane still be the way to land this? The alternatives are:

- You land on top of your fuel tanks and use a crane to get down.
- You land underneath the fuel tanks which are supported by legs and the engines are out wide.
- You have have a descent rocket stage which you dump just prior to landing and landing is done with very small fuel tanks.

The skycrane literature suggests that if you know your surface (as landing at a base) to don't need skycrane.

Offline Jim

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Re: Skycrane: Way to go or one off experiment
« Reply #26 on: 08/09/2012 11:21 am »
I do wonder if more than 1 of these parachutes can be used at once now it's been tested on Mars.

Good tech should be used again.  :)

no, because they would interfere with each other.  Not the same as subsonic parachutes.

Offline Robotbeat

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Re: Skycrane: Way to go or one off experiment
« Reply #27 on: 08/10/2012 03:20 pm »
I do wonder if more than 1 of these parachutes can be used at once now it's been tested on Mars.

Good tech should be used again.  :)

no, because they would interfere with each other.  Not the same as subsonic parachutes.
Subsonic ones can also interfere with each other, too, of course.

One of the guys who modeled the MSL parachute (who was my professor) also did a lot of work with the interaction between multiple parachutes. I agree it's a complicated problem and is probably best solved by using a bigger monolithic parachute.

Another way to solve it is to accept a higher terminal velocity, using more delta-v with the skycrane maneuver (for larger payloads, it may make sense to use biprop, though for smaller payloads the added dry mass of a biprop system would outweigh the Isp advantage).
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Offline manboy

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Re: Skycrane: Way to go or one off experiment
« Reply #28 on: 08/10/2012 05:27 pm »
Is this a feasible technique for 10 tons.
No, its not scalable. But the Skycrane could be used for future missions.
"Cheese has been sent into space before. But the same cheese has never been sent into space twice." - StephenB

Offline Robotbeat

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Re: Skycrane: Way to go or one off experiment
« Reply #29 on: 08/10/2012 06:13 pm »
Is this a feasible technique for 10 tons.
No, its not scalable. But the Skycrane could be used for future missions.
Based on what do you say that the sky crane maneuver is not scalable to 10 tons?

If you're not an established expert (and even if you are), you should provide a reason.

The heatshield may not be scalable, the parachute might not be scalable (other things being equal), but why not the skycrane maneuver? I see no reason.
Chris  Whoever loves correction loves knowledge, but he who hates reproof is stupid.

To the maximum extent practicable, the Federal Government shall plan missions to accommodate the space transportation services capabilities of United States commercial providers. US law http://goo.gl/YZYNt0

Offline alexterrell

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Re: Skycrane: Way to go or one off experiment
« Reply #30 on: 08/11/2012 07:38 pm »
Is this a feasible technique for 10 tons.
No, its not scalable. But the Skycrane could be used for future missions.
Based on what do you say that the sky crane maneuver is not scalable to 10 tons?

If you're not an established expert (and even if you are), you should provide a reason.

The heatshield may not be scalable, the parachute might not be scalable (other things being equal), but why not the skycrane maneuver? I see no reason.
I can't see any limit to the scalability of the skycrane manoeuvre (tricky word to spell!).

However, at some point you would no longer need it for stability. Legs might be preferable at that point.

In theory you could lower an Ocean liner this way. 

Offline ClaytonBirchenough

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Re: Skycrane: Way to go or one off experiment
« Reply #31 on: 05/24/2013 03:08 pm »
I was wondering what the MSL payload to around -7km MOLA would be. MSL landed approximately 900kg to -4.4 km MOLA. So my question is what would the payload be if MSL were to land at an area that was -7km MOLA?
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Offline Russel

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Re: Skycrane: Way to go or one off experiment
« Reply #32 on: 06/07/2013 02:02 pm »
I was wondering what the MSL payload to around -7km MOLA would be. MSL landed approximately 900kg to -4.4 km MOLA. So my question is what would the payload be if MSL were to land at an area that was -7km MOLA?

Which raises the interesting question of where on Mars can you land a rover that's relatively low in altitude but still feasible to drive the rover (remotely) to somewhere interesting that people might land?

Where I'm wondering about sky cranes is in landing a rover that carries methane fuel plus oxygen plant. And could it manage a long traverse on the Carbon monoxide fuel it would generate as a byproduct.

Online MickQ

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Re: Skycrane: Way to go or one off experiment
« Reply #33 on: 06/10/2013 12:23 am »
Would Hellas not be an interesting place to land ???  2300 klm across, high probability of caves, ancient rivers flowed into the basin and the rock that made it in the first place.

Mick.

Offline Russel

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Re: Skycrane: Way to go or one off experiment
« Reply #34 on: 06/14/2013 04:25 pm »
A couple of thoughts here.

Suppose we had a Mars lander/ascent vehicle that was brought down to the bare minimum in mass. Say, 5 tonnes dry mass, with crew and life support. Such a vehicle would require in the order of 13 tonnes of methane/lox fuel for ascent.

That's roughly 3 tonnes of methane.

Suppose also that we take the attitude that we don't want to do any complex synthesis for fuel for ascent, but we'll simply produce oxygen - which is 77 percent of the mass needed.

Now, getting that 3 tonnes of methane landed on Mars is the issue. That and a simple oxygen production plant. You can see where I'm going here.

Its an ISPP on wheels with a methane tank. All up about 5 tonnes landed mass.

That, I think, is a candidate for an upscaled skycrane landing.

The other thing that arises is, what do we do with the used skycrane(s)? I've yet to think of a use for one that makes overall sense - like an ascent vehicle. But with a bit of good design they could make for good spare parts.

Online MickQ

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Re: Skycrane: Way to go or one off experiment
« Reply #35 on: 06/15/2013 07:35 am »
As I understand it, the Skycrane was designed to land a scientific payload on ground that was not contaminated by the rocket exhaust.  A manned lander or ISRU unit would not need this level of care and may actually benefit from a cleaner landing site.

Mick.

Offline Jim

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Re: Skycrane: Way to go or one off experiment
« Reply #36 on: 06/15/2013 12:51 pm »
As I understand it, the Skycrane was designed to land a scientific payload on ground that was not contaminated by the rocket exhaust.  A manned lander or ISRU unit would not need this level of care and may actually benefit from a cleaner landing site.

No, that was only a benefit.  The Skycrane technique (it is not a vehicle) eliminated the need to roll off the lander. It can be used to place any package on the surface.  with that said, it is not good for a manned lander

Offline Russel

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Re: Skycrane: Way to go or one off experiment
« Reply #37 on: 06/15/2013 01:54 pm »
As I understand it, the Skycrane was designed to land a scientific payload on ground that was not contaminated by the rocket exhaust.  A manned lander or ISRU unit would not need this level of care and may actually benefit from a cleaner landing site.

Mick.

That has me scratching my head. When Curiosity landed they still ended up with bits of gravel on top of it. If I remember correctly, one of the reasons for hanging it from a cable was also stability - the rover could find its own level, whilst the skycrane part could remain with a vertical attitude.

It would still be an advantage to use the landing engine to sweep the site. One option of course is to have the skycrane firmly attached, come in low, perform a "sweep" operation (basically rotate) and then ascend somewhat and then lower the payload.

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