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Robotic Spacecraft (Astronomy, Planetary, Earth, Solar/Heliophysics) => Mars Science Laboratory (MSL) and Mars 2020 Rover Section => Topic started by: Kaputnik on 02/27/2021 06:17 pm

Title: Skycrane future developments discussion thread
Post by: Kaputnik on 02/27/2021 06:17 pm
Please use this thread to discuss the EDL hardware and procedures used in the Curiosity and Perseverance missions, and to suggest improvements and how the system could be evolved.

I'll kick it off with this:

The descent stage will remain a one use vehicle for as long as there is no way of manufacturing hydrazine on Mars. Change my mind.
Title: Re: Skycrane future developmeI guess they could land tankernts discussion thread
Post by: Rocket Science on 02/27/2021 06:30 pm
I guess they could land tanker ships with drop tanks...
Title: Re: Skycrane future developments discussion thread
Post by: edzieba on 02/28/2021 09:33 am
Any mass put on the descent stage/skycrane is mass you've taken from the rover (the actual payload) mass budget. Landing legs, extra cameras, extra computers, extra propellant, etc. All of that mass is stolen from the object you actually want to land, in order to 'save' what is in effect a glorified parachute.
Title: Re: Skycrane future developments discussion thread
Post by: Mader Levap on 02/28/2021 12:19 pm
There is nothing to improve, since completely different landing system is needed if we want to go beyond one scientific rover per 10 years.
Title: Re: Skycrane future developments discussion thread
Post by: Jim on 02/28/2021 02:13 pm

So, are you saying that a Descent Stage built more than 10 years ago was made in a way that cant be improved?

Yes, that is why they reused the DTM Descent Stage.  There was little improvement to be done by building a new using lessons learned.


That it's impossible to design today a Descent Stage with the same T / W, even using the same engines if you will, but carrying more equipment to provide a controllable soft landing?


Correct.  There is no room in the same 15 foot diameter aeroshell to add more propellant and still fly the same size rover.  If more propellant is to be reserved for landing the descent stage and more mass added to the descent stage, then mass has yo be removed from the rover.


I know it can. And that's why we are saying that looking to a future project with the mind in an old one is not what was pointed out here.


No, you don't.    The Mars 2020 rover and descent stage are a fixed mass system and are constrained by the volume of the Mars 20210 15 foot diameter aeroshell and the Mars 2020 parachute system.  No more mass can be delivered to the surface of Mars using the Mars 2020 hardware.  I specifically listed Mars 2020 everywhere because that is what we are talking about.  I am not talking about using the skycrane maneuver on a future mission with a different launch vehicle, different aeroshell and different spacecraft.  It is impossible to modified the Mars 2020 descent stage to allow it to land without taking mass from the rover using the same aeroshell.

And yes, we are talking about flying hardware, in an atmosphere, with gravity. So the Descent Stage it's not a spacecraft, it's more an aircraft than a spacecraft. With different variables, but with the same principles.

You could not be more wrong.  The descent stage is a spacecraft much like the Apollo Lunar Module and it is far from an aircraft.   Aerodynamics play no role in its operation.  The rocket equation rules everything with its operation.  Aerodynamics play a role during the entry and the parachute portion of the mission.  But once the Powered Descent Vehicle (PDV) is released from the backshell, it is all rocket propulsion and no aerodynamic.  The descent stage doesn't even have aerosufaces.  And it fails to mean the definition of an aircraft "An aircraft is a vehicle that is able to fly by gaining support from the air.".  Nope, all rocket propulsion.

And we will see another one performing a Skycrane maneuver, for sure.


You have nothing to base that statement on.  Nothing, no inside knowledge, no professional knowledge, no even educated guess.


Anyways, I'm convinced that, for some reason, it's impossible to debate here. It's more like a "convince Jim" thread than a Perseverance thread. I prefer not to play that game.

It isn't impossible to debate here.  It is just impossible to post statements that are not defendable without getting called on it.


Title: Re: Skycrane future developments discussion thread
Post by: Jim on 02/28/2021 03:28 pm
Visual aids

The rover and descent stage which are in the green rectangle and are constrained by the volume of the aeroshell (A & B) and the mass braking ability of the aeroshell and the parachute (in the container designated by the arrow).
Title: Re: Skycrane future developments discussion thread
Post by: Stan-1967 on 02/28/2021 04:02 pm
This discussion spun off from the aesthetic insult some contributors felt about the descent stage crashing. 

My aesthetics are more interested in the potential for mass to be shaved off any future descent element so more instruments can be included on the rover/payload portion.

From what information I could find,  it seems like the fly away descent element is throttled pretty low when landing.  The 8 engines and structure seem pretty beefy and overpowered.  This makes sense for the first efforts with Curiousity & Perseverence,  but what now?   

What lessons have been learned that may contribute better mass efficiency to future mission like sample return or prepositioned equipment for human exploration?

Title: Re: Skycrane future developments discussion thread
Post by: Kaputnik on 02/28/2021 04:42 pm
Is the "throttled down" observation maybe related to the ability to have engine-out capability on the descent stage?
Title: Re: Skycrane future developments discussion thread
Post by: Jim on 02/28/2021 05:25 pm

From what information I could find,  it seems like the fly away descent element is throttled pretty low when landing.  The 8 engines and structure seem pretty beefy and overpowered.  This makes sense for the first efforts with Curiousity & Perseverence,  but what now?   

What lessons have been learned that may contribute better mass efficiency to future mission like sample return or prepositioned equipment for human exploration?


This is only for rovers and not sample return.
Title: Re: Skycrane future developments discussion thread
Post by: libra on 02/28/2021 06:00 pm
The attached paper explain why and how we are trapped with the present EDL system, harcking back to Viking 45 years ago.
Every single parameter is on the edge of present state-of-the-art / tech.

A lot, if not all, parameters are heavily stacked against Mars E-D-L systems.

- aeroshell diameter, because shrouds, because rockets diameter

- parachute / skycrane / retrorocket landing sequence

- Mars, its atmosphere, and its landscape.

It is an excellent reading, even if 15 years old. Not that far away since they were preparing Curiosity back then, and Mars 2020 is an improved variant of it.

One example of a damning EDL parameter: Mars landscape. The volcanoes and their "bulge", compared to Mars as a whole, are so huge - one half of the planet is 3 to 5 km, average, higher than the other one.
As far as present E-D-L systems go, that difference amounts to the difference between a successfull gentle landing and a Mach 3 crash right into Mars solid ground.

The atmosphere, too, is a [female dog, rude word] with seasonal fluctuations of its thickness, and its difficulty to fill a parachute even at Mach 2 or more.

Plenty of things like that, the paper explains extremely well.
Title: Re: Skycrane future developments discussion thread
Post by: Stan-1967 on 02/28/2021 09:20 pm
Thanks for linking the IEEE paper.  It states much of what I think Jim was holding back on, & he may know even more recent directions of what paths for Mars EDL are currently favored.  For certain advancements have been made in the area of making  retropropulsion & HIAD devices viable for heavier payloads.

It seems like Mars exploration is a pivot point where the current EDL using the Descent Element+ Skycrane maneuver is very close, if not already over.  ( at least for USA & ESA missions, no idea about China's intent) 

Concepts for the sample retrieval rover & sample return look to perform EDL within the current constraints on aeroshell size, but will land more like Viking or Pathfinder Phoenix.  Beyond that, there are no planned missions with the possible exception of the astrobiology laboratory.  Whatever comes after these missions, if anything, will probably depend on how interesting Mars is for science & human exploration. 

Skycrane, as currently constrained, seems completely inadequate for any human exploration needs.  If Perseverance or any other missions fail in finding compelling biosignatures, I could see the scientific community lose interest in prioritizing Mars & move on to Europa, Enceladus, & Titan.  If any of them do find biosignatures, Skycrane type delivery of payloads to the surface still look to be inadequate & will be surpassed by newer methods.


edited per Jim's note below.  Mars Pathfinder used airbags, my recollection was incorrect.   I was thinking of the Phoenix lander.
Title: Re: Skycrane future developments discussion thread
Post by: Jim on 02/28/2021 09:32 pm
, but will land more like Viking or Pathfinder.


Not like Pathfinder ever again
Title: Re: Skycrane future developments discussion thread
Post by: Stan-1967 on 02/28/2021 09:53 pm
, but will land more like Viking or Pathfinder.


Not like Pathfinder ever again

Jim's memory is better than mine.  I meant to say "Phoenix" lander, not Pathfinder. 

At least I didn't suggest we land via the method of Mars Polar Lander
Title: Re: Skycrane future developments discussion thread
Post by: Blackstar on 02/28/2021 10:11 pm
Jim's memory is better than mine.  I meant to say "Phoenix" lander, not Pathfinder. 

At least I didn't suggest we land via the method of Mars Polar Lander

MPL and Phoenix and InSight all used the same lander hardware.
Title: Re: Skycrane future developments discussion thread
Post by: Cherokee43v6 on 02/28/2021 10:32 pm
One thing I've seen mentioned from time to time on these forums is an ISRU Hopper.

I could see the Skycrane's thrust structure being used as the basis for such a lander, with the ISRU package depended below, giving the structure the necessary ground clearance for repeated takeoff and landing cycles.

Of course it would require a complete redesign of the rocket motors since they are currently hypergolics rather than an ignited mixture such as metholox that is the most commonly mentioned ISRU fuel.
Title: Re: Skycrane future developments discussion thread
Post by: Stan-1967 on 02/28/2021 10:35 pm
Jim's memory is better than mine.  I meant to say "Phoenix" lander, not Pathfinder. 

At least I didn't suggest we land via the method of Mars Polar Lander

MPL and Phoenix and InSight all used the same lander hardware.

I was more referring to the part where MPL had a high velocity event with the surface of Mars.  :) 
Title: Re: Skycrane future developments discussion thread
Post by: LouScheffer on 02/28/2021 11:38 pm
It is impossible to modified the Mars 2020 descent stage to allow it to land without taking mass from the rover using the same aeroshell.
I too agree that modifying the descent stage for a soft landing is not particularly useful.

However, it's certainly not impossible.  JPL made a number of tradeoffs, sensibly in my mind, gaining simplicity but sacrificing performance.  These could be made otherwise to gain margin to land the descent stage.

First, could you squeeze more fuel in the descent stage?  There is certainly room (see below).  Then how about mass margin?   Currently the descent stage uses pyro valves to keep propellant from moving from tank to tank until the final descent.  It also uses ejecting masses (about 300 kg of them) to move the center of gravity off center, then center it again later in the descent.  Instead, JPL could use the pressurization sequence to move liquid fuel from tank to tank, changing the center of gravity, then move it back again.  This would reduce the needed ejectable masses, directly increasing the mass margin.  But it's extra complexity in an already complex sequence.

More generally, JPL chose a monopropellant for simplicity.  A bi-propellant descent stage would only need 300 kg of propellant as opposed to the 400 kg they used.  (Plus the tanks would be lighter both due to smaller size and lower pressure - most biprop engines work at 20 bar, as opposed to the 46 bar of the JPL engines.)  This would leave plenty of margin to land the descent stage.

Finally, their descent profile is designed to be as safe as possible, not to use the minimum fuel.   A more hoverslam-type landing would use less fuel, leaving more for post-rover-dropoff maneuvers. 

Once again, I don't think these changes are a good idea.  But there is certainly slack in the system - the descent stage had reliability in mind, not the utmost possible performance.   As a side effect of this philosophy, the performance could be increased by modifications, if there was a need.
Title: Re: Skycrane future developments discussion thread
Post by: Vultur on 02/28/2021 11:45 pm
Whatever comes after these missions, if anything, will probably depend on how interesting Mars is for science & human exploration. 

And what happens with SpaceX's plans...

Quote
If Perseverance or any other missions fail in finding compelling biosignatures, I could see the scientific community lose interest in prioritizing Mars & move on to Europa, Enceladus, & Titan.

Well - if they remain limited to current mission types, possibly yes. But I think if human missions to Mars are happening, bringing those scientific payloads along (small mass in comparison) would be a lot cheaper & would keep happening.

I think what happens with Mars science post-Perseverance will be determined by whether SpaceX's human Mars plans succeed or fail.
Title: Re: Skycrane future developments discussion thread
Post by: Stan-1967 on 03/01/2021 12:19 am

And what happens with SpaceX's plans...


Well - if they remain limited to current mission types, possibly yes. But I think if human missions to Mars are happening, bringing those scientific payloads along (small mass in comparison) would be a lot cheaper & would keep happening.

I think what happens with Mars science post-Perseverance will be determined by whether SpaceX's human Mars plans succeed or fail.

SpaceX's plans are irrelevant to any future Skycrane developments.

I think your point may be retro-propulsive landings will obsolete everything else.  Maybe...maybe not...that is a possibility, however current missions like sample return are paced towards later this decade.  Even if SpaceX succeeded with landing on Mars tomorrow, nothing is in the NASA, ESA, JAXA or any other agencies pipeline for science missions that would take advantage of that.  ( I could be unaware of it , but haven't heard of anything)
Title: Re: Skycrane future developments discussion thread
Post by: AstroWare on 03/01/2021 12:35 am
Whatever comes after these missions, if anything, will probably depend on how interesting Mars is for science & human exploration. 

And what happens with SpaceX's plans...

Quote
If Perseverance or any other missions fail in finding compelling biosignatures, I could see the scientific community lose interest in prioritizing Mars & move on to Europa, Enceladus, & Titan.

Well - if they remain limited to current mission types, possibly yes. But I think if human missions to Mars are happening, bringing those scientific payloads along (small mass in comparison) would be a lot cheaper & would keep happening.

I think what happens with Mars science post-Perseverance will be determined by whether SpaceX's human Mars plans succeed or fail.
I think there is a possible future where human missions (like SpaceX, but not exclusively) and robotic missions like Perserverence can work together.

Planetary protection issues: if nasa wants pristine samples from special areas, a Rover, sent direct to the zone is preferred. Perserverence is this kind of system.

Sample return: as nasa sample return mission architecture shows, there is a high cost per kilogram returned to earth. That is where manned missions can help. Picking up curated samples from designated caches. This would only constitute a small piece of the manned mission but huge scientific reward.

Rovers like Percy can be sent ahead of manned missions to collect samples before possible contamination. But beyond that, There is Prospecting. If orbital surveys are sufficient to prospect landing sites, that's great. But it's a big risk too. Ground truth measurements from Landers could bring down that risk prior to human missions.

All this is to say -
In this future I think further use and development of the skycrane system is worthwhile, even in a future with starship.
Title: Re: Skycrane future developments discussion thread
Post by: Jim on 03/01/2021 12:53 am

First, could you squeeze more fuel in the descent stage?  There is certainly room (see below).  Then how about mass margin?   

Wrong, there is no mass margin.  And there is no room for larger tanks


Instead, JPL could use the pressurization sequence to move liquid fuel from tank to tank, changing the center of gravity, then move it back again.

No, not viable.  Too slow.  And there is no real good way to measure the mass moved and regulate gas pressures at multiple levels.

 

This would reduce the needed ejectable masses

All the extra plumbing, flow meters, regulators, etc would likely negate any savings and just increase complexity with no real benefits.

 
A bi-propellant descent stage would only need 300 kg of propellant as opposed to the 400 kg they used.  (Plus the tanks would be lighter both due to smaller size and lower pressure - 
 

That would be wrong.  A biprop system would weigh more with the extra tanks and propellant lines.  The higher density of NTO would make balancing the descent stage problematic.   Try finding room for 4 or 6 tanks.  What biprop thrusters meet the mission requirements?

Then there is the matter of roll thrusters type and plumbing .  The operating pressure of the tanks has little effect on their mass in the days of composite overwrap.


And again, your statement "This would leave plenty of margin" is unsupported.

 
Finally, their descent profile is designed to be as safe as possible, not to use the minimum fuel.   A more hoverslam-type landing would use less fuel, leaving more for post-rover-dropoff maneuvers. 
 

Wrong.  A hover slam does not save propellant.  It is used when the engines can't throttle low enough and still have a T/W>1.  It actually uses more propellant because a larger than necessary engines are used.

The hover slam does not allow for obstacle avoidance.  The descent profile is to allow for maneuvering to avoid bad landing areas.   And there is the divert maneuver, required to avoid the back shell and parachute.

No slack in the system, just somebody throwing darts at the wall.
Title: Re: Skycrane future developments discussion thread
Post by: Vultur on 03/01/2021 02:34 am
SpaceX's plans are irrelevant to any future Skycrane developments.

I think your point may be retro-propulsive landings will obsolete everything else.  Maybe...maybe not...that is a possibility, however current missions like sample return are paced towards later this decade.

More that if a continuous human presence is established on Mars, separately-launched-and-landed science spacecraft might no longer be a thing (instead carrying the science payloads, rovers, etc. along with the human missions).

I agree already planned missions wouldn't necessarily be affected, but given the lead time, we should know whether the SpaceX plan is working before those missions are done (Musk has talked about Mars landing in 2025... even pushing that out two synods for "Elon time", that's still this decade).
Title: Re: Skycrane future developments discussion thread
Post by: Zed_Noir on 03/01/2021 03:19 am
<snip>
SpaceX's plans are irrelevant to any future Skycrane developments.
<snip>
Even if SpaceX succeeded with landing on Mars tomorrow, nothing is in the NASA, ESA, JAXA or any other agencies pipeline for science missions that would take advantage of that.  ( I could be unaware of it , but haven't heard of anything)

Well, there is a slight possibility that SpaceX might launch a prototype EDL (Entry, Descend & Landing) test Starship to Mars in the 2022 launch window. Presuming the Starship make it through entry and drops below hypersonic speed. It could eject a number Skycrane type vehicles  along it's landing path. But again it's a slight possibility there will be a Mars bound Starship launching in 2022, never mind any exotic Starscrane type vehicles.


SpaceX itself could have basic scientific payloads in development to support their future Mars missions. Something like a Martian weather station that can also measure various radiations. SpaceX is also capable of mass producing payloads just like the Starlink comsat bus components.
Title: Re: Skycrane future developments discussion thread
Post by: Kaputnik on 03/01/2021 06:15 am
I recall that there was a suggestion to replace the balance masses with a circulating liquid mercury system. Did anybody (Jim?) know how far that idea got? Obviously sounds like a lot of extra complexity for marginal gain, but perhaps a future growth path.
Title: Re: Skycrane future developments discussion thread
Post by: libra on 03/01/2021 06:54 am
It is interesting to analyze SpaceX Mars EDL system in the light of the Braun paper I linked. The paper dates from 2006 just when Musk launched its first Falcon 1. And a section of the paper is pondering how to get from MSL 1 metric ton to Human Space Flight 100 metric ton. Quite a leap !

I wonder if Musk red this paper, probably yes. One can see how  trying to land 100 times more he ran straight into "Mars versus EDL" issues.

At the beginning (Red Dragon ?) Musk wanted to go 100% propulsive, just like on the Moon - and a bit like Falcon 9, using retropropulsive rocketry (note: the paper mentions supersonic retro-propulsion, nearly a decade before Falcon 9 2013-2016 gradual mastering of it !)
Doing as if Mars atmosphere was thin enough, it simply did not existed. But Mars atmosphere did not agree, and would readily burn any such lander. Alternatively, it would burden it with an enormous amount of propellant.
In both cases: Mars versus Musk: 1-0 for Mars.
Even Musk had to concede to Mars, and accept some hypersonic glide. In turn, this led to the present SN-8 / SN-9 flight profile - with the skydive manoeuver, and hypersonic entry / glide, Shuttle style. Except there is no Shuttle Landing Strip on Mars, so back to a vertical landing...

Mars EDL is hard, because Mars is so damn unforgiving.
Title: Re: Skycrane future developments discussion thread
Post by: Don2 on 03/01/2021 09:04 am
How difficult would it be to put an 8.4m fairing on a Falcon Heavy or a Vulcan rocket? It seems that Mars landed missions could benefit from this, as would future space telescopes.

This would work for things that need the extra width but don't need the mass capability of SLS.
Title: Re: Skycrane future developments discussion thread
Post by: ugordan on 03/01/2021 01:06 pm
Once again, I don't think these changes are a good idea.  But there is certainly slack in the system - the descent stage had reliability in mind, not the utmost possible performance.

Is that "slack", though? Isn't the tradeoff between reliability and performance a constant struggle and one which the engineers always have to decide on?

You can take a higher-performing, but more risky system (say biprop), add redundant components to it which will increase reliability, but also increase mass hence reducing its performance gain over a simpler, but inherently more reliable system. Rarely can you have your cake AND eat it.
Title: Re: Skycrane future developments discussion thread
Post by: baldusi on 03/01/2021 03:38 pm
Finally, their descent profile is designed to be as safe as possible, not to use the minimum fuel.   A more hoverslam-type landing would use less fuel, leaving more for post-rover-dropoff maneuvers. 
 

Wrong.  A hover slam does not save propellant.  It is used when the engines can't throttle low enough and still have a T/W>1.  It actually uses more propellant because a larger than necessary engines are used.

[...]

A Hoverslam might not be desirable for the SkyCrane system, but assuming you already have the thrust sizing, it does reduce propellant requirements because it reduces the gravity losses. It works specially well if you are at terminal velocity. So, it does makes sense for Falcon 9, and does reduces propellant usage for that case. But is completely inapplicable for SkyCrane.
Title: Re: Skycrane future developments discussion thread
Post by: lrk on 04/15/2021 04:59 pm
At the beginning (Red Dragon ?) Musk wanted to go 100% propulsive, just like on the Moon - and a bit like Falcon 9, using retropropulsive rocketry (note: the paper mentions supersonic retro-propulsion, nearly a decade before Falcon 9 2013-2016 gradual mastering of it !)
Doing as if Mars atmosphere was thin enough, it simply did not existed. But Mars atmosphere did not agree, and would readily burn any such lander. Alternatively, it would burden it with an enormous amount of propellant.
In both cases: Mars versus Musk: 1-0 for Mars.
Even Musk had to concede to Mars, and accept some hypersonic glide. In turn, this led to the present SN-8 / SN-9 flight profile - with the skydive manoeuver, and hypersonic entry / glide, Shuttle style. Except there is no Shuttle Landing Strip on Mars, so back to a vertical landing...

Mars EDL is hard, because Mars is so damn unforgiving.

That's not at all accurate - Red Dragon would have performed a lifting aerodynamic entry and used its launch abort engines for the final deceleration, just like MSL/Mars 2020 and others.  A fully propulsive Mars EDL would require an impractical amount of propellant. 

Red Dragon definitely could have worked, but would have scaled up poorly - the Starship design does do more of the deceleration aerodynamically, enabling a better payload fraction.  Additionally Red Dragon was canceled after propulsive landing was deleted from Dragon 2, as modifying Dragon for Mars entry would have required even more one-off engineering effort that could be better spent on developing the next system. 
Title: Re: Skycrane future developments discussion thread
Post by: baldusi on 04/25/2021 01:55 pm
Little note regarding Red Dragon: they inverted the angle of attack, so they used the aerodynamic forces pointing down. This allowed them to bleed more energy. How? Because to get more time of atmosphere drag, they needed shallow entry angles, but at those speed they would skip over the atmosphere. So, by inverting the angle of attack they actually avoided skipping and could bleed more speed.
I do wonder if they will use a similar trick with Starship.
Title: Re: Skycrane future developments discussion thread
Post by: Explorer33 on 10/12/2022 03:20 pm
I'm hoping that someone is still monitoring this tread... I'm coming in from the "Will a Starship head to Mars in the 2024 launch window" thread.. I need some help on Skycrane capabilities, who designed, and can I get one for a Starship mission to Mars. :) Skycrane is the only available and proven technology that can put something on the surface of Mars. So I would like to know how "independent" were/are it's capabilities from the Rovers which it lowered to the surface? And possibly a few other questions like could it work with the ESA Rover? Thx.
Title: Re: Skycrane future developments discussion thread
Post by: edzieba on 10/12/2022 06:11 pm
Little note regarding Red Dragon: they inverted the angle of attack, so they used the aerodynamic forces pointing down. This allowed them to bleed more energy. How? Because to get more time of atmosphere drag, they needed shallow entry angles, but at those speed they would skip over the atmosphere. So, by inverting the angle of attack they actually avoided skipping and could bleed more speed.
I do wonder if they will use a similar trick with Starship.
Some years ago now, but one of the ELD simulations at IAC 2017 showed inverted flight (35:32):
https://youtu.be/tdUX3ypDVwI?t=2132
However, this was when Starship used a PICA-X derivative, and ablative TPS was a different optimal EDL profile than the radiative TPS currently installed on Starship: Ablative TPS prefers minimising total thermal load but accepts higher peak heating, whereas radiative TPS needs to minimise peak heating but can tolerate greater total heat soak.
Title: Re: Skycrane future developments discussion thread
Post by: ccdengr on 10/12/2022 06:55 pm
So I would like to know how "independent" were/are it's capabilities from the Rovers which it lowered to the surface?
Not very independent, the descent stage had just enough autonomy to execute the flyaway after the cables to the rover were cut.  Nearly all of the control was happening in the rover computer, which had to communicate with the sensors (IMU, radar) and prop system in the descent stage.  Using a different rover with this system would be very challenging.
Title: Re: Skycrane future developments discussion thread
Post by: Kaputnik on 10/12/2022 08:31 pm
Skycrane is the only available and proven technology that can put something on the surface of Mars.

Well that's not really true. The MPL/Phoenix/inSight platform is another option, and the MER system whilst coming up on 20yrs old is not exactly ancient history.
You've also got the Schaparelli lander platform which came fairly close to succeeding, just iron out the bugs.
And then of course the Chinese have been highly successful although 'available' might not apply to a Western project.

The Skycrane method was developed specifically for delivering a large rover. It has the advantage of placing the rover directly on the surface without the need for ramps and a risky egress manoeuvre. But that trades off against using the payload as the landing gear (no sacrificial shock absorbers!), the risk of the multiple tether reels, and the propellant needed for the hover and fly away. There were plenty of people turning blue during Curiosity's landing...
Title: Re: Skycrane future developments discussion thread
Post by: Jim on 10/13/2022 01:02 am
I'm hoping that someone is still monitoring this tread... I'm coming in from the "Will a Starship head to Mars in the 2024 launch window" thread.. I need some help on Skycrane capabilities, who designed, and can I get one for a Starship mission to Mars. :) Skycrane is the only available and proven technology that can put something on the surface of Mars. So I would like to know how "independent" were/are it's capabilities from the Rovers which it lowered to the surface? And possibly a few other questions like could it work with the ESA Rover? Thx.

Again, here is no hardware called 'skycrane".  It is called the descent stage.
JPL designed and built.  JPL isn't taking orders.
Questions here don't change the answers posted on other threads.
Rover controls everything.

ESA rover unlikely.  It wasn't made for craning or launching upside down
Title: Re: Skycrane future developments discussion thread
Post by: Explorer33 on 10/13/2022 01:57 pm
Hi Jim, long time no see...  Actually, Jim and I met recently on the Orion thread, and there he told me there was no such thing as skycrane. Imagine my surprise when I can across a thread called, "Skycrane future developments discussion thread".  ;) and even bigger surprise to find him here.
But all jesting aside, appreciate the responses. I did kind of suspect that Perserverance had all the smarts. So, one of the things appropriate for this thread is how to turn the "descent stage" into a more "general purpose" Mars cargo delivery system - doubt that NASA will want to rely solely on Starship to drop things on the surface - by adding the sensors, nav and landing smarts into the descent stage (see Jim, I called it descent stage and not skycrane  :))
Do you think JPL would be onboard for making more and adding the necessary smarts? In time for 2024 mission?
They should also change their disposal method from "flyaway and litter the surface" to "flyaway and neatly land"?
Do you think two years is enough time for ESA to convert ExoMars Rover into a Descent Stage package?
Title: Re: Skycrane future developments discussion thread
Post by: Jim on 10/13/2022 03:38 pm
Do you think JPL would be onboard for making more and adding the necessary smarts? In time for 2024 mission?
They should also change their disposal method from "flyaway and litter the surface" to "flyaway and neatly land"?
Do you think two years is enough time for ESA to convert ExoMars Rover into a Descent Stage package?

Nope, none of this is feasible.
JPL would not be onboard for any of this.  They have Europa Clipper in 2024. 
Changing the disposal method would require much more propellant and also the addition of landing gear.
Converting ESA rover is not really a possibility.  Completely different load paths (hanging vs sitting).
Title: Re: Skycrane future developments discussion thread
Post by: Kaputnik on 10/18/2022 01:56 pm
Hi Jim, long time no see...  Actually, Jim and I met recently on the Orion thread, and there he told me there was no such thing as skycrane. Imagine my surprise when I can across a thread called, "Skycrane future developments discussion thread".  ;) and even bigger surprise to find him here.
But all jesting aside, appreciate the responses. I did kind of suspect that Perserverance had all the smarts. So, one of the things appropriate for this thread is how to turn the "descent stage" into a more "general purpose" Mars cargo delivery system - doubt that NASA will want to rely solely on Starship to drop things on the surface - by adding the sensors, nav and landing smarts into the descent stage (see Jim, I called it descent stage and not skycrane  :))
Do you think JPL would be onboard for making more and adding the necessary smarts? In time for 2024 mission?
They should also change their disposal method from "flyaway and litter the surface" to "flyaway and neatly land"?
Do you think two years is enough time for ESA to convert ExoMars Rover into a Descent Stage package?

I started the thread and used the term 'Skycrane' since that way everybody knows what it's about. Lots of spacecraft  have descent stages.

Anyway...
1) The Skycrane system is designed for landing a large rover directly on the surface. The principal advantage is that you avoid a tricky and risky egress manoeuvre using long ramps. But you pay for it in greater propellant margin for the hover and flyaway, and the risk of the bridles and tethers not deploying correctly. For a static lander is not the optimal solution. There is already a general purpose design for that, which was used by MPL, Phoenix, and inSight.

2) What 2024 mission?

3) What benefit is there from soft landing the descent stage? MSL and Perseverance were launched by expendable vehicles, everything except the payload is discarded along the way. Why single out the descent stage for special treatment?
Title: Re: Skycrane future developments discussion thread
Post by: deadman1204 on 10/18/2022 07:21 pm

3) What benefit is there from soft landing the descent stage? MSL and Perseverance were launched by expendable vehicles, everything except the payload is discarded along the way. Why single out the descent stage for special treatment?

If the decent stage lands, then you still have all the egress problems (because the rover needs to drive off of/leave the lander still). So it gives both sets of problems - landing a multi-ton object softly, and also having all the egress issues.
Title: Re: Skycrane future developments discussion thread
Post by: Explorer33 on 10/19/2022 02:36 pm
Just one word - Litter... In the next decade there will probably be more Mars landings (attempted) than all the previous 60 years combined. We have already seen Perserverance coming across "pieces" of the descent stage, parachute threads, etc. The Mars surface will begin to be like low earth orbit - littered - not with dead satellites, but with hundreds of fragmented pieces of EDL technologies. Just suggesting that a soft landing is preferred over a RID (Rapid Intentional Disassembly). Eventually, we should make that a requirement in the PP protocols.
Alas I digress... Jim has injected a sober amount of realism into my fanciful ideas to re-using existing technologies of Skycrane and ESA's Rover in a Starship trip to Mars. Accepted; today's technologies are very, very specific to their original designs and not readily adaptable to alternative plans. Accordingly, on the "Will a Starship head to Mars in the 2024 launch window" thread, those ideas/thoughts/possibilities are now identified as "investigated and discarded".
And, for this thread, would agree with others that a "standardized" version of Skycrane that contained the landing smarts and soft-landing capability (with or after cargo delivery) would be a worthy goal and a valuable long-term asset to Mars exploration. Hurry, several could be utilized in the 2024 launch window! :)
Title: Re: Skycrane future developments discussion thread
Post by: Kaputnik on 10/20/2022 03:17 pm
Just one word - Litter...

There's a part of me that is kind of glad that it's becoming a go-to reaction to not want to litter the universe with man-made junk. I get it. I'm appalled by what we've done to our own planet.

But seriously, it's not going to do any harm on Mars. No life forms will be harmed by some bits of mylar etc. And the cost of trying to do something 'tidily' on Mars is enormous. Just getting a spacecraft down there safely ranks as amongst the hardest technological challenges that humans have ever attempted.
Thought experiment: you want to soft land the descent stage. Ok, that means adding extra propellant and a set of sensors and computers so that it can achieve controlled flight. So you've added a fair chunk of mass.
That ripples through the whole system. Now you need a bigger parachute, backshell, and heat shield, all of which are going to end up discarded on the surface. You're actually *adding* to the 'litter'.
It doesn't stop there. You need a bigger launch vehicle. That's using up more of earth's resources, putting more pollution in to earth's atmosphere, and dumping more hardware in to the ocean. And these are things with a measurable effect upon a biosphere, unlike dropping some expended hardware on another, lifeless, planet.

If you want to actually do something useful, look at Earth.
Title: Re: Skycrane future developments discussion thread
Post by: Jim on 10/20/2022 07:34 pm
  Hurry, several could be utilized in the 2024 launch window! :)

Who is to hurry?
Title: Re: Skycrane future developments discussion thread
Post by: Explorer33 on 10/20/2022 09:52 pm
Hi Jim, the "Hurry" was more of a generic shout-out to the universe. But now that you made me think about it, I suppose it is mostly for this thread which is discussing "Skycrane future developments" and then for someone who will convince a company - JPL, SpaceX, Grumman - to design and build: the Mars Surface Cargo Delivery {Ship? Truck? Vehicle?} which is like a Skycrane, but with a few more sensors for NAV and landing, a couple more pounds of fuel to cover a non-RID soft-landing and added elements, and a brain to direct it all, resulting in a "single-use, general purpose Mars surface delivery system for ~1Ton cargo loads". Are you in? Just think, with this and a standardized Rover platform, we could be dropping Rovers all over the place. :)
Title: Re: Skycrane future developments discussion thread
Post by: Kaputnik on 10/21/2022 10:08 pm
Hi Jim, the "Hurry" was more of a generic shout-out to the universe. But now that you made me think about it, I suppose it is mostly for this thread which is discussing "Skycrane future developments" and then for someone who will convince a company - JPL, SpaceX, Grumman - to design and build: the Mars Surface Cargo Delivery {Ship? Truck? Vehicle?} which is like a Skycrane, but with a few more sensors for NAV and landing, a couple more pounds of fuel to cover a non-RID soft-landing and added elements, and a brain to direct it all, resulting in a "single-use, general purpose Mars surface delivery system for ~1Ton cargo loads". Are you in? Just think, with this and a standardized Rover platform, we could be dropping Rovers all over the place. :)

There may be an argument for a multi-purpose payload delivery system, if there are enough payloads.
There is no argument in favour of soft landing it as the default.
Title: Re: Skycrane future developments discussion thread
Post by: Jim on 10/24/2022 07:07 pm
Hi Jim, the "Hurry" was more of a generic shout-out to the universe. But now that you made me think about it, I suppose it is mostly for this thread which is discussing "Skycrane future developments" and then for someone who will convince a company - JPL, SpaceX, Grumman - to design and build: the Mars Surface Cargo Delivery {Ship? Truck? Vehicle?} which is like a Skycrane, but with a few more sensors for NAV and landing, a couple more pounds of fuel to cover a non-RID soft-landing and added elements, and a brain to direct it all, resulting in a "single-use, general purpose Mars surface delivery system for ~1Ton cargo loads". Are you in? Just think, with this and a standardized Rover platform, we could be dropping Rovers all over the place. :)

Who is going to pay them?
Title: Re: Skycrane future developments discussion thread
Post by: deadman1204 on 10/24/2022 07:53 pm
Hi Jim, the "Hurry" was more of a generic shout-out to the universe. But now that you made me think about it, I suppose it is mostly for this thread which is discussing "Skycrane future developments" and then for someone who will convince a company - JPL, SpaceX, Grumman - to design and build: the Mars Surface Cargo Delivery {Ship? Truck? Vehicle?} which is like a Skycrane, but with a few more sensors for NAV and landing, a couple more pounds of fuel to cover a non-RID soft-landing and added elements, and a brain to direct it all, resulting in a "single-use, general purpose Mars surface delivery system for ~1Ton cargo loads". Are you in? Just think, with this and a standardized Rover platform, we could be dropping Rovers all over the place. :)

There may be an argument for a multi-purpose payload delivery system, if there are enough payloads.
There is no argument in favour of soft landing it as the default.
More than paying them to make so many sky cranes (or even a generic design), who is gonna pay for all the payloads? They cost more than the skycrane. 500-1000kg payloads to mars are not cheap. Perseverance and curiosity took years (and over a billion dollars and a decade each).
Something like a generic skycrane would come about due to need. If there are enough missions, its a worthwhile investment. NASA/ESA simply don't have the money to make a generic sky crane with no use planned, and then try to justify it afterwards.
Title: Re: Skycrane future developments discussion thread
Post by: Blackstar on 10/25/2022 02:07 pm
Perseverance and curiosity took years (and over a billion dollars and a decade each).

I think both missions were at least $2.5 billion apiece (I have vague memories that Perseverance came in at $2.8 billion, and you'd have to adjust the earlier mission for inflation). Somebody more industrious than me can look up the costs. The point is that they're expensive.
Title: Re: Skycrane future developments discussion thread
Post by: Explorer33 on 10/27/2022 07:37 pm
Hi Jim, Blackstar and Deadman1204, well you are bringing up some really annoying realities - and I mean that in a good way. In the end, it is about the money, and I never dreamt those Rover Programs cost so much. I was thinking commercial-esk, not remembering that there aren't any commercial programs for Mars. At least for LEO (LowEarthOrbit), NASA has established Commercial Cargo & Crew, which has enabled SpaceX and others to enter that market with re-useable launch, cargo and crew capsule tech. Hopefully Mars will see some commercialization to bring repeatability, design reuse, standards for delivery size/weight/EDL, and best of all - reduced cost. But, I'm guessing, that NASA is not about to request proposals for my dream "Standard Skycrane 1-Ton Mars Surface Cargo Delivery Vehicle". So, I will take back to the "Will a Starship head to Mars in the 2024 Launch Window" thread, the conclusion that the proposal to have Starship put something on the surface with Skycrane tech is not possible given the limited amount of time, unavailability of key experienced vendor resources, unique-ness of the design, and the high cost.