Help - Search - Members - Calendar
Full Version: Skycrane
Unmanned Spaceflight.com > Mars & Missions > MSL
Pages: 1, 2, 3, 4, 5, 6
MarsEngineer
Soooo Mike C., it was all YOU? Actually both Wayne and I should have known better, you were right in the middle of it. (this is one of the downsides of invisible voice-only communication). Please accept my apologies.

(One handy thing about MSSS .... just say "Mike" and you get a good fraction of the team to look your way! Ken is way out-numbered).

I know very well that you and many others did a huge amount of work to get that link working. If getting UHF during EDL was a "historical footnote" it was a pretty big footnote as far as I am concerned. It was the first time at Mars that two spacecraft on relatively independent "missions" actually talked to each other ! (Viking orbiters and landers were all the same team). That is much harder than it looks to get right and nearly impossible to test. What's more we used MGS's UHF link for getting rover data down nearly every day for months.

For folks listening in, we used the MGS UHF relay during Spirit and Opportunity's EDL so that we would have some real diagnostic data in the .... ahem ... unlikely? .. chance that we had a bad day. The link worked waaaay better than any of us dared hope. My hat's off to the MGS/MOC team (the MOC team flew and operated the "Mars Ballon Relay" radio). Had we really had a bad Spirit EDL day, the data we received through MGS would have been worth its weight in gold (especially with Opportunity landing only 3 weeks later - there was quite a lot we could have done to "fix" EDL problems, even with only 3 weeks to go).

-Rob

PS Mike I heard all went well at the CDR for the zoom lens. We are cheering for you!

**********************
Opinions expressed here are the author's and do not represent the views of NASA, JPL nor Caltech.
akuo
Mike and Rob,

It's amazing to see our space heroes talking about the mission like this on the forum. Moreover because I did follow that event live through NASA-TV, listening intently to every word you guys said.

What is the plan with MSL? Will there be tones and/or a UHF link during EDL?
climber
QUOTE (akuo @ May 30 2007, 02:21 PM) *
Mike and Rob,

It's amazing to see our space heroes talking about the mission like this on the forum. Moreover because I did follow that event live through NASA-TV, listening intently to every word you guys said.

What is the plan with MSL? Will there be tones and/or a UHF link during EDL?


akuo, I guess we can even ask for a direct link to UMSF mars.gif

BTW, I agree with you : I love this discussion.
djellison
I think the plan is the same for both Phoenix and MSL - not DTE tones, but UHF relay to one or both orbiters.
AlexBlackwell
QUOTE (akuo @ May 30 2007, 02:21 AM) *
It's amazing to see our space heroes talking about the mission like this on the forum.

Maybe Mattel will be coming out with Mike Caplinger and Rob Manning action figures shortly, which would be a nice complement to the LEGO and Hot Wheels Mars collectibles laugh.gif
MarsEngineer
Somehow I doubt engineer action figures would sell well even if the pocket saver accessory was included (plus the plastic beard would be creepy).

You are close Doug, PHX EDL will only communicate via UHF to both MRO and ODY. The X-band radio stays on the cruise stage and suffers a nasty fate. MSL will use BOTH X-band ("tones") direct to Earth (DTE) and UHF all the way down, however there are proposed landing sites where the X-band DTE link is very poor (Earth too low on the horizon).

FYI the reason we use "tones" is because the normal X-band data modulation technique does not work when a vehicle's antenna is swinging and decelerating in an unpredictable manner. The DSN's receivers "expect" that the X-band carrier is stable in order to detect it. EDL is the opposite of stable. So instead we send the X-band carrier as well as one of 256 subcarrier frequencies (tones). We record this signal "open loop" in special receivers (designed to do radio science). Whenever a new event is detected by the rover software on board (sent on 10 second intervals), the EDL software will select one of the 256 tones to indicate what is going on then. Each event is assigned ia unique tone. So when the software has detected that the radar is in lock, it will send the tone assigned to that event. Because each tone is sent on 10 s boundaries, we get the most recent event that could be as much as 10 seconds old. Not great but pretty good. Special software was designed to read the recorded signal and "decode" the tone into its unique number. We used Jason Willis' "magic decoder ring" to get from the number to the event name in real time on landing day.

Because the UHF data is buffered inside the rover's electronics as well as in the UHF radio, even at "high" data rates (8 kbps) it takes a while - more than 10 seconds - before data measured inside the rover actually gets out of the antenna and on its way to the orbiters for relay to earth. So ironically the very slow tones (1 tone per 10 seconds) are actually quicker at detecting bad things going wrong inside the vehicle than UHF is. The trick is in figuring out what events to code into a tone.

We also get Doppler effect (frequency changes) due to some key events like parachute deployment (easy to see) and RAD fire (harder to see). On Spirit, Polly Estabrook (my hero) and I could not quite make out the RAD fire, put parachute deployment was clear. On Opportunity, we both could see the bump that the RAD created in the X-band carrier frequency. That was fun.

-Rob Manning

**********************
Opinions expressed here are the author's and do not represent the views of NASA, JPL nor Caltech.
AlexBlackwell
QUOTE (MarsEngineer @ May 30 2007, 07:53 AM) *
Somehow I doubt engineer action figures would sell well even if the pocket saver accessory was included (plus the plastic beard would be creepy).

I don't know, Rob. For you, I think all that's needed is to modify a classic G.I. Joe (ca. 1970s), and include, in addition to the comm headsets, pocket protectors, slide rules, etc., a trumpet laugh.gif
djellison
I actually have "RAD has fired..." from the MERB coverage as my windows startup message. I think that actually breaks the Marsgeekometer.

Doug
dvandorn
And don't forget a flannel shirt, Alex. For some reason, I always imagine Rob wearing blue jeans and a flannel shirt... smile.gif

-the other Doug
elakdawalla
Actually, he's usually better dressed than that. smile.gif
http://www.planetary.org/image/rrgtm_studa...ning5_print.jpg

--Emily
djellison
To print MOC images like this we have a print that's THIS big smile.gif

Doug
dvandorn
Oh, I'm positive he is, Emily, and I mean no disrespect, Rob. Maybe it's simply that you have that "lumberjack" look that makes one think of blue jeans and flannel shirts... in any event, I really can't remember where I got that impression from. I couldn't cite you a particular time or image in which I've seen you wearing that. It's just always how I picture you when I read your posts, here.

-the other Doug
Phil Stooke
Doug:

"I actually have "RAD has fired..." from the MERB coverage as my windows startup message. I think that actually breaks the Marsgeekometer."

Wanting to do it puts a severe strain on the geekometer, Doug, but knowing how to do it puts you over the top.

Phil
climber
QUOTE (MarsEngineer @ May 30 2007, 07:53 PM) *
We also get Doppler effect (frequency changes) due to some key events like parachute deployment (easy to see) and RAD fire (harder to see). On Spirit, Polly Estabrook (my hero) and I could not quite make out the RAD fire, put parachute deployment was clear. On Opportunity, we both could see the bump that the RAD created in the X-band carrier frequency. That was fun.

That has been fun for us too!
It'll be even more fun watching you (and hearing Mike's voice biggrin.gif ) on Phoenix and MSL landing wink.gif
AlexBlackwell
QUOTE (dvandorn @ May 30 2007, 09:51 AM) *
... in any event, I really can't remember where I got that impression from...

Undoubtedly, it must stem from the fact that, generally speaking, the planetary sciences/engineering community is among the worst dressed group of professionals you'll ever meet. There are exceptions, of course, but sartorial elegance is a rarity.

If you don't believe me, try attending an LPSC.
hendric
QUOTE (MarsEngineer @ May 30 2007, 12:53 PM) *
Somehow I doubt engineer action figures would sell well even if the pocket saver accessory was included (plus the plastic beard would be creepy).


I dunno, technogeeks can be very superstitious (odd, I know), and an idol of someone who knows what he's doing might sell as a good luck totem. Maybe I should start selling WWRMD? coffee mugs and bumper stickers on cafepress to gauge the interest. laugh.gif
nprev
QUOTE (hendric @ May 30 2007, 02:35 PM) *
I dunno, technogeeks can be very superstitious (odd, I know)...


Not at all odd, I'd say. These missions are so complex, with so many discrete things happening and possible compounding failure modes thereby that any effort to try to influence random events seems like a reasonable and prudent risk mitigation strategy.

(Yes, I inserted a paraphrase of a Spock quote from the original series...gotta assert my pocket protector! smile.gif )
Juramike
QUOTE (nprev @ May 30 2007, 06:47 PM) *
These missions are so complex, with so many discrete things happening and possible compounding failure modes thereby that any effort to try to influence random events seems like a reasonable and prudent risk mitigation strategy.



Translation: "Better lucky than good."

wink.gif
lyford
QUOTE (AlexBlackwell @ May 30 2007, 01:48 PM) *
Undoubtedly, it must stem from the fact that, generally speaking, the planetary sciences/engineering community is among the worst dressed group of professionals you'll ever meet.

I dunno, the entire MER team looks rather nattily attired in this photo. biggrin.gif

On topic again, I notice that the captions for the new MSL Video definitely call the descent stage hardware by the name of "sky crane." No mention of any "maneuver," Corbomite or otherwise. (sorry, just had to throw in a ST:TOS reference for the ubergeek debate.)

Not sure who didn't get the memo on this smile.gif
Click to view attachment Click to view attachment
Click to view attachment Click to view attachment

In that last frame however, I think an argument could me made for calling the descent stage "The Flying Spaghetti Monster."
dvandorn
QUOTE (lyford @ May 30 2007, 06:33 PM) *
In that last frame however, I think an argument could me made for calling the descent stage "The Flying Spaghetti Monster."

You'd best be wearing Pirate regalia when you say that, fella! laugh.gif

-the other Doug
lyford
Well, MSL does utilize an ARRRRRRRGH-T-G. tongue.gif
centsworth_II
QUOTE (lyford @ May 30 2007, 07:33 PM) *
I notice that the captions for the new MSL Video definitely call the
descent stage hardware by the name of "sky crane." No mention of
any "maneuver," Corbomite or otherwise.

Ouch! I don't want to hear a lot of griping on these pages if
the general press "can't get it right."
Analyst
Will there be an attempt to soft land the descent stage after dropping the rover or will it simply fly away until its tanks are empty? I know there is nothing to learn scientificly from this but maybe the enginering community can gain some kwowledge (This is science too.). Plus there is no risk, "only" extra effort (cost) mainly in software development I assume.

Analyst
djellison
The plan as I understand it (and Rob confirmed this) is to let the decent stage fly away uncontrolled and crash itself.

Adding the complexity of making it controlled after getting rid of the payload is un-necessary. You would have to have all the systems that the decent stage uses onboard MSL ( I'm assuming the brains of the operation will be within MSL with a cable up to the decent stage for throttles, a gyro and an accelerometer - I over simplify but that's the basics if I understand it right. ) That chance of the decent stage ending up splatting on top of MSL is probably less than the chance of the first MER bounce recontacting the backshell and chute.

A bad analogy is the MER lander. The rover's WEB was the brains of the whole operation - backshell/lander/etc etc was essentially just dumb - hooked up to the web with relays and so on. Once the final cable was cut - the lander was dead - although to be fair it didn't have big thrusters with a few gallons of hydrazine sloshing about.

A similar discussion's happening in the MSL Video thread.

Doug
climber
QUOTE (Analyst @ May 31 2007, 08:32 AM) *
Will there be an attempt to soft land the descent stage after dropping the rover or will it simply fly away until its tanks are empty? I know there is nothing to learn scientificly from this but maybe the enginering community can gain some kwowledge (This is science too.). Plus there is no risk, "only" extra effort (cost) mainly in software development I assume.
Analyst

MER's computers was all in the rover's vehicules (not in the secent stage) and I wonder if there will be any computer in MSL the descent stage to fly it after MSL will be released.

Edit : my post has been written at the same time as Doug's but, as he's the Boss, his has been released a bit before tongue.gif
Analyst
So the last signal from the rover computers a split of a second after the cut of the three load carrying cords will be "fly away, full trust up and to the left", followed by umbilical release?

Even then some kind control (and power) is needed in the descent stage to keep valves open etc. and have some kind of controlled fly away. I guess you are pretty fast out of control with four trusters firing and your CG shifting (propellant consumption). Add wind and you probably need a computer in it for control. You probably need gyros in the descent stage, if only for the skycrane part. So imho the descent stage needs its own computer (and already has gyros and truster control).

Analyst
Jim from NSF.com
1. The descent stage does have batteries to handle the power requirements from cruise stage sep to landing
2. The valves could be locked open
3. CG doesn't really shift, the tanks are symmetrical
4. no computer, all in the rover
5. It is like MER. MER had batteries, an IMU and radar* in the lander, so does MSL

It is brainless as it flies away


* and descent camera
AndyG
QUOTE (Jim from NSF.com @ May 31 2007, 12:57 PM) *
It is brainless as it flies away

Hopefully it won't have the "luck" any Wile E. Coyote-purchased ACME vehicle would almost certainly come with. ohmy.gif

How much fuel/what's the expected flight-time following the release of MSL? Are we talking "a few seconds" or more?

Andy
djellison
QUOTE (Phil Stooke @ May 30 2007, 08:54 PM) *
Doug:
Wanting to do it puts a severe strain on the geekometer, Doug, but knowing how to do it puts you over the top.


smile.gif


Doug
Juramike
I gotta admit, when I first heard the concept of the Skycrane, I was really skeptical. But after the excellent discussion in this thread, (“whoa! the design-dudes themselves are breakin’ it down for us! – man, I love this place!”) I’m convinced this plan is absolutely brilliant.

If it works, it would provide a reliable delivery system that could be used to put anything, (anybody?) down on the Martian surface, without having to worry about landing ramps, airbag or chute debris, or legs or uneven terrain.

How scalable is this? How big could it go? Could you put down a future habitation module on Mars, deep drilling rigs, other cool stuff?

Could you use it to put down multiple instruments in different (but fairly close, locations?) [OK, you’d need to upgrade to more propellant, brains in the platform, and deal with COG issues]

Could you use it to move an instrument already on the surface to a new location? [lotsa propellant, more brains in the platform, getting the rendezvous and “hook up” – but heck, the stability, lowering problems will already have been solved] (Imagine if we could send a Skycrane pick up Oppy and move her to another location within a 200 km radius – this would really change the post-Victoria discussion!)

Could it be used to deliver other packages down on other (airless) planetary surfaces [no chute, but using much, much more retro]? (Europa, for example).



Could this become the equivalent of an interplanetary FedEx truck?

Just "Wow"!! ohmy.gif ohmy.gif ohmy.gif

-Mike
hendric
Here's another name to add to the Skycrane/Marscrane mix: Carryall!

Those are the airships from Dune used to lift the harvesters and drop them on top of new spice beds. It's very fitting, with Arrakis == Mars, and looking for spice == looking for water.

smile.gif
centsworth_II
QUOTE (hendric @ May 31 2007, 12:32 PM) *
Carryall!

Sounds like something the mars widow constituency could identify with.Click to view attachment
AlexBlackwell
QUOTE (hendric @ May 31 2007, 06:32 AM) *
Here's another name to add to the Skycrane/Marscrane mix: Carryall!

Odds are that NASA will run another one of its famous naming contests, so don't be surprised if the rover and descent stage both end up getting named something hokey like, for example, "Perseverance" and "Courage."
dvandorn
You're probably right -- heck, I would have been good with the MERs being officially named Duck Dodgers and Marvin!

I would really rather see the project managers name the vehicles, just as the crews were allowed to name their vehicles during Mercury and Apollo. After all, what's the worst that ever came out of that? Charlie Brown, Snoopy and Casper? Those names caught the public's imagination, regardless of how silly they might have sounded to some self-important bean counter.

I doubt they'll give a separate name to the descent stage, though. You don't name something that you're going to just let crash... and yes, I know they deliberately crashed the LM ascent stages. But those were going to be named, no matter what. They never named the third stages that they crashed into the Moon, after all...

-the other Doug
AlexBlackwell
QUOTE (dvandorn @ May 31 2007, 08:53 AM) *
You're probably right -- heck, I would have been good with the MERs being officially named Duck Dodgers and Marvin!

You know things are flaky when geological features have better names than the exploration vehicle biggrin.gif

QUOTE (dvandorn @ May 31 2007, 08:53 AM) *
I doubt they'll give a separate name to the descent stage, though. You don't name something that you're going to just let crash...

Perhaps, but NASA gave names to the ISS nodes and airlock, so I wouldn't be surprised if they gave separate names for MSL's parachute, backshell, and heatshield.
MarsEngineer
You guys crack me up! biggrin.gif


As for my clothes, having been a son of a canadian and growing up in the wilds of northwest Washington state, I once had a penchant for jeans, plaid and duct tape, however I have discovered that said accoutrement is not ammenable to marital bliss. My wonderful wife has far better taste than I and she has helped me overcome my predelictions and I am happier for it.

Doug needs to help me with changing my startup beep to say "get a life!". Maybe he can also help me with my dang VCR - DVD recorder .... I only have so many brain cells left - nerdom steals them away. blink.gif

With regard to the JPL captioned video that labeled the descent stage the "skycrane" .... *I* may be the one in the wrong ... I sent an email to Adam.

By the way Doug, I read in this and the Video thread a ton of wonderful recent conversations & questions surrounding MSL EDL & skycrane. Is this the right thread to post "answers"? I would be up for posting (on occasion) to a single thread. (although there are far more questions & comments than I have time to answer - at least in the next few weeks).

-Rob

PS I do not fault those who are concerned about the "odd" MSL landing architecture, however rightly or wrongly, the same people who created Pathfinder and MER EDL are squarely behind the MSL design. In fact they are many of the same people. I am one. I will have to write up how we got to it someday. (In my unwritten book that only engineers and UMSFers would find interesting.)



**********************
Opinions expressed here are the author's and do not represent the views of NASA, JPL nor Caltech.
djellison
The two threads have contracted chronic topic overlap smile.gif I think we can keep MSL EDL stuff in here, and we can just go "ooo - pretty - nice rendering of Chute deployment - Dan always cheated on that bit!" in the Video thread.

Doug
Matt Francis
Odds are that NASA will run another one of its famous naming contests, so don't be surprised if the rover and descent stage both end up getting named something hokey like, for example, "Perseverance" and "Courage."

I read that too fast and saw that as "Cougar" and thought "Now there's a badass name for a landing system...The COUGAR!"
climber
QUOTE (MarsEngineer @ May 31 2007, 11:55 PM) *
With regard to the JPL captioned video that labeled the descent stage the "skycrane" .... *I* may be the one in the wrong ... I sent an email to Adam.


Rob, I guess you're talking about this Adam smile.gif :http://www.unmannedspaceflight.com/index.p...amp;#entry80800
You'd better tell him that UMSF'ers can be anywhere biggrin.gif
PhilHorzempa
QUOTE (Matt Francis @ Jun 1 2007, 12:17 AM) *
Odds are that NASA will run another one of its famous naming contests, so don't be surprised if the rover and descent stage both end up getting named something hokey like, for example, "Perseverance" and "Courage."

I read that too fast and saw that as "Cougar" and thought "Now there's a badass name for a landing system...The COUGAR!"



I agree that, sadly, NASA will probably give a nice, pathetic name to the MSL. I do like
"Cougar." In another thread, I suggested "Avatar."

Here is the link to a thread for MSL names -

http://www.unmannedspaceflight.com/index.p...c=3667&st=0


I also agree that Program Managers should name their spacecraft. It seems
to work well in the Discovery, New Frontiers and Mars Scout programs.


Another Phil
stevo
I’m not sure where to put this. I heard a talk from Adam Steltzner today. Most of it was on EDL simulation, which was intriguing but far from my field. With the understanding that I am paraphrasing outrageously, and apologies if this is old news, here are some snippets I remember (didn’t have the wits to take notes).

He reiterated what we’ve heard before about airbags not really being an option for MSL, it’s just too big. In a photo of his team behind Sojourner, a MER, and the MSL mockup, Sojourner was roughly the size of one of MSL’s wheels.

He also had an interesting comment on the sky crane thingy that I haven’t heard elsewhere. Systems like Viking etc. where the engines are on the lander itself must keep going until the very moment of touchdown, until the lander puts a toe on the ground, and then turn off immediately. Sort of a hair trigger. The descent stage on sky crane will continue descending below this point, “into the ground” a little to ensure that the lander (hope I’m using the right terms) is down safely. Thus no Mars Polar Lander-style oops. It sounded like the trigger is going to be based on the amount of throttle needed to maintain a constant descent rate.

Since the spacecraft comes in “hot” ie: under control rather than ballistically (?), it apparently needs to be asymmetrically weighted, thus a 200kg tungsten weight is ejected early on in the descent. This apparently raised some questions along the lines of “You’re taking 200kg of tungsten all the way to Mars just so you can throw it away when you get there …?”

In response to a question, he said the three most exciting things he’d learned about Mars were that it was windier, wetter (past tense, I think) and rockier than they expected. Or maybe flatter?

On landing sites, he said that people were enamored with the Southern highlands early on, but the “follow the water” motto naturally led them to lower northern elevations. The spec. is for 1 km MOLA, but apparently the sites currently being considered are below this anyway. This is just as well, since the mass of the vehicle has progressively increased from an original value of about 550kg to probably 900kg by the time they’re done. The landing ellipse is on the order of 10 km across, thus people keep proposing trenches and craters that are 10.5 km across. Nila Fossae makes the grade, but a crater whose name escapes me missed the cut because 2.2% of their EDL simulations ended with an excessive descent speed against the crater wall.

He’s an engaging speaker and had an appreciative audience. And what looks like a great job.

Stephen
Jim from NSF.com
QUOTE (stevo @ Jun 22 2007, 03:11 PM) *
1. He also had an interesting comment on the sky crane thingy that I haven’t heard elsewhere. Systems like Viking etc. where the engines are on the lander itself must keep going until the very moment of touchdown, until the lander puts a toe on the ground, and then turn off immediately. Sort of a hair trigger. The descent stage on sky crane will continue descending below this point, “into the ground” a little to ensure that the lander (hope I’m using the right terms) is down safely. Thus no Mars Polar Lander-style oops. It sounded like the trigger is going to be based on the amount of throttle needed to maintain a constant descent rate.

Since the spacecraft comes in “hot” ie: under control rather than ballistically (?), it apparently needs to be asymmetrically weighted, thus a 200kg tungsten weight is ejected early on in the descent. This apparently raised some questions along the lines of “You’re taking 200kg of tungsten all the way to Mars just so you can throw it away when you get there …?”


The descent stage is thrusting until the rover (vice lander) is on the ground

Symmetrically bodies need offset an CG to produce lift. Hence the need for ejecting mass is to go from a "balanced" spin stablized spacecraft in the cruise mode to an "unbalanced" lifting body.

I guess he didn't mention that another set of masses will be ejected just before parachute deploy to bring everything back into balance for the remainer of the descent
AlexBlackwell
QUOTE (stevo @ Jun 22 2007, 09:11 AM) *
I heard a talk from Adam Steltzner today...He’s an engaging speaker and had an appreciative audience.

Thanks for being UMSF Correspondent for a Day, Stephen. The update is appreciated, and I agree, Steltzner is a very good briefer.

Hey, maybe Doug needs to start issuing press badges for UMSFers attending these events biggrin.gif
stevo
QUOTE (AlexBlackwell @ Jun 22 2007, 01:59 PM) *
Thanks for being UMSF Correspondent for a Day, Stephen. The update is appreciated, and I agree, Steltzner is a very good briefer.

Hey, maybe Doug needs to start issuing press badges for UMSFers attending these events biggrin.gif

My pleasure. And thanks Jim, for the elaborations. The more I learn about these programs, the more I am impressed by the work that goes into them, and the people responsible. Fabulous stuff.
Stephen
MarsEngineer
QUOTE (climber @ Jun 1 2007, 05:00 AM) *
Rob, I guess you're talking about this Adam smile.gif :http://www.unmannedspaceflight.com/index.p...amp;#entry80800
You'd better tell him that UMSF'ers can be anywhere biggrin.gif


Sorry for the delayed response ...

I looked at your link and I got a good laugh. Yep, that's the same Adam. He and a few of the MSL EDL gang travel in packs. cool.gif He was probably off to one of our meetings at HQ to help explain why this "sky crane thingy" was going to work last Jan.

Adam is leading the MSL EDL team (I am not this time round). And I agree that he is an excellent speaker. He has a lot of energy and enthusiasm as well as a good story to tell. (Do you remember him in the NOVA show where he described the parachute inflation "squidding" failure during the Ames wind tunnel testing as a "mega bummer"? I was there and even then I thought that expression was funny. It helped chase the butterflys away.) He is a fun guy too. They whole gang is fun to work with. (I miss working with them every day ... I only see them about once a week or less these days ... Phoenix dominates my time for the moment).

Someone asked if we thought that the sky crane architecture was portable to other Mars (and non-Mars) lander designs. Although I retain hope that that will indeed be the case, the jury is still out. We still have a lot of work to do before we nail this design down. The MSL terminal descent and landing architecture (of which the sky crane maneuver is a part) is experiemental and there is much we need to learn yet. For example, the details of the guidance law in the descent stage that controls the "fly away" maneuver is still being developed.

I know that there has been some debate here second guessing whether or not the descent stage has, should have or needs to have its own computer. To save cost and complexity we had orginally opted for an FPGA design without a processor, however that now has changed due to the threat that there might need to be more "smarts" in the descent stage to deal with further fly-away complexity after the rover has landed and has separated. The descent stage has its own processor, but it shares the EDL job with the rover's computer. They work together as a team. The rover is definitely in charge however.

Cheers,

-Rob Manning
Stu
QUOTE (MarsEngineer @ Jul 7 2007, 10:33 PM) *
The descent stage has its own processor, but it shares the EDL job with the rover's computer. They work together as a team. The rover is definitely in charge however.


You know, this is sounding more like one of the Transformers every day... blink.gif
nprev
Aha! Good news, Rob, and a wise move in my opinion. Been trying to figure out just how the hell the descent stage was gonna keep flight-stable long enough to go away & crash elsewhere after cutting MSL loose...a little brains here should go a long way. smile.gif

QUOTE (MarsEngineer @ Jul 7 2007, 02:33 PM) *
For example, the details of the guidance law in the descent stage that controls the "fly away" maneuver is still being developed.

Tilt it 5 deg any direction after bridle separation & keep going until the fuel's gone...? cool.gif
climber
You won't say Skycrane's crazy after this : http://www.agilous.com/view/Videos/Crazy/C...gs-from-Boeing/
dvandorn
Sorry to resurrect an old thread, but at the beginning of this thread (back three and a half years ago), it was noted that the MSL descent strategy (the skycrane maneuver) was dependent on the success of ground tests planned for the summer of 2005.

The fact that the skycrane maneuver is still the official plan for MSL's EDL (emphasis on the L) tells me that those tests must have been successful. But there was not a single post about the results of those tests in this thread, or in any thread that I can recall.

Does anyone know how the tests were conducted, and what the actual results of those tests were? Was the descent stage design adjusted due to those results? Are there any areas of concern that were addressed in design after the tests, and if so, are there things we ought to be looking at during the descent to make sure those areas of concern were properly addressed?

Very curious...

-the other Doug
centsworth_II
QUOTE (dvandorn @ Nov 13 2008, 01:15 PM) *
...at the beginning of this thread (back three and a half years ago), it was noted that the MSL descent strategy (the skycrane maneuver) was dependent on the success of ground tests planned for the summer of 2005.

From these 2006 articles, it looks like testing of individual components would be done, but not the whole system.

"At present, MSL project officials don't see any full-up and costly hover tests of the Sky Crane here on Earth. Pieces of the system, like the parachute and Viking-class retro-rocket engines on the Sky Crane framework can be individually tested. 'We think we can do a pretty good job of piecing it together,' Cook emphasized."http://www.cnn.com/2006/TECH/space/01/18/m...tory/index.html

"Steltzner said NASA has a vigorous validation and test plan mapped out for every element of the Sky Crane landing system. The agency ultimately must rely on a combination of integrated hardware testing and simulation to feel confident that the system will work in the only environment that counts--Mars.
'That's par for the course in this job,' Steltzner said. 'We never really get to do a full end-to-end test of any of the [entry, descent and landing] systems for Mars because we are not on Mars. This one is not any different.' "
http://www.space.com/businesstechnology/06...l_skycrane.html
This is a "lo-fi" version of our main content. To view the full version with more information, formatting and images, please click here.
Invision Power Board © 2001-2024 Invision Power Services, Inc.