SpaceX demonstrated supersonic retro-propulsion
One of the traditional bugaboos about designing a Mars lander has been the problem of supersonic retro-propulsion. This is a problem since any reasonable aeroshell has a terminal velocity of several Mach. So you need either supersonic retro-propulsion or heavy parachutes to brake to subsonic first (and then subsonic retro-propulsion). The original Mars Voyager proposals in the 1960s used supersonic retro-propulsion, but JPL couldn't get it to work. So, when a half-size Mars Voyager was resurrected as Viking, a supersonic parachute was added. All subsequent JPL landers/rovers have used this design. I recall Rob Manning giving a presentation to us JPL interns in 2006 saying that supersonic retro-propulsion would be the best thing for Mars EDL, but that noone knew how to get it working.That was until last month. On the first Falcon 9 v1.1 flight, SpaceX demonstrated supersonic retro-propulsion on the first stage (that was the part of the recovery that actually worked). If SpaceX really have cracked the code on this, then they will be able to land much easier on Mars than any proposals since the Mars Voyager days.
I'd heard that payloads about the size of the MSL are about as big as can be done with the existing types of EDL systems, as the parachute becomes too big to deploy reliably or something. (I remember something like that). So to go larger, new EDL Systems are needed. Mostly likely, replacing the parachutes with more retropropulsion for deceleration.
I think there's a couple ways possibly around the issue if firing an engine into the thin Martian supersonic slipstream if that's a problem.One is to have a big jettisonable aeroshield, with retro engines protected behind it. When the engines are lit, the shield kicks off and impacts the surface. That way the engines don't light into a supersonic slipstream. I would think once they are lit and pressurized, the thin Martian air wouldn't be able to to enger the nozzle and be a problem. The exhaust plume expelled out the bottom should overpower and basically split the slipstream.
Another is something like RedDragon where the nozzles are tucked back just out of the slipstream and the heatshield creates a bit of a splash efffect in the atmosphere (see picture below as well). As long as those nozzles are tucked in enough, they shouldn't have supersonic Martian air coming into them I don't think. I would guess this is the concept behind why RedDragon's superdraco's are expected to work for landing on Mars.If so, you can scale that up with larger engines. Perahps bigger methalox enignes in a scaled up geometry of Dragon. It's not as efficient to have engines positioned like that because of their outward angle. But it should hopefully be feasibel for landing purposes. A Mars ascent vehicle of some sort can have engines directly under it for better efficiency for ascent.
Horizontal lander. It's a much better configuration for use after landing and has many advantages during EDL as well.
The problem with capsules is that you'd need huge diameters. The MSL had already a 4.5m diameter heat shield.You could go full-propulsive but in that case the payload mass fraction is rather pathetic. In the paper above the baseline vehicle is 60t in low Mars orbit, of which 8.7t are payload delivered to the surface. Of course those 60t need to be transported from LEO to LMO, which brings total LEO departure mass to around 350t (ISP of 350s).
A few documents.The Challenge for Mars EDL (presentation):http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20100017668_2010017622.pdfMars Exploration Entry, Descent and Landing Challenges (paper):http://www.ssdl.gatech.edu/papers/conferencePapers/IEEE-2006-0076.pdfFully-Propulsive Mars Atmospheric Transit Strategies forHigh-Mass Payload Missions (paper):http://www.ssdl.gatech.edu/papers/conferencePapers/IEEE-2009-1219.pdf------------------------------------------------------------------------------------------The problem with capsules is that you'd need huge diameters. The MSL had already a 4.5m diameter heat shield.You could go full-propulsive but in that case the payload mass fraction is rather pathetic. In the paper above the baseline vehicle is 60t in low Mars orbit, of which 8.7t are payload delivered to the surface. Of course those 60t need to be transported from LEO to LMO, which brings total LEO departure mass to around 350t (ISP of 350s).
^I just wanted to delete my previous comment. Full-propulsive in this case means no significant heatshield requirement, but IMO its kind of pointless.For example the Austere Human Mission to Mars uses 13m diameter landers with ~53t payload:http://trs-new.jpl.nasa.gov/dspace/bitstream/2014/41431/1/09-3642.pdfA combination of heatshield and retropropulsion.
See the 2:40 mark of the video in the first post. The lander, which clearly masses considerably more than the Apollo Lunar Module, is deploying not one but 3 parachutes. These deploy after the back aeroshell is left behind, allowing the parachutes to unfurl. As the parachutes unfurl the descent engines kick in. I believe Steven Pietrobon mentioned that this approach chops the descent delta-v required from the engines to a mere 500 m/s. That's an impressively low figure for landing something 50 mt or more on Mars. I don't know what the figure would be doing an all-propulsive approach, but it'll be significantly more than that.
I'm curious, but are all the Mars landers you envision Mars Orbit Rendezvous types or would you ever consider a direct ascent lander? I ask because the rough estimates are that a 9-Raptor per core Falcon X Heavy would fling more than 110 mt through TMI. It's so much mass you could feasibly pull it off. Of course the problem I see is getting back off of Mars.
http://www.angelfire.com/md/dmdventures/orbitalmech/DeltaV.htmFrom To Delta-V (km/s) LEO Mars Surface 4.8LEO Lunar surface 6.2Mars LMO 4.4LMO Mars 0.05LMO Earth return 3.4Lunar surface LEO 3.2Total delta-v required To Mars surface and back to Earth: 22 km/s (12.6 km/s required for everything beyond LEO) To lunar surface and back to Earth 18.8 km/s (9.4 km/s required for everything beyond LEO) It seems pretty clear from the math that Spacex or anyone else for that matter would be hard-pressed to pull off a Mars direct ascent approach. It'd work superbly if all they cared about was getting payloads to the surface of Mars though. Matter of fact, it requires only 77.4% of the delta-v needed (beyond LEO) to land on the Moon for you to land on Mars. Now if only there wasn't that dire fact about half of all missions to Mars ending in failure adding a huge asterisk to that. My guess is if that if anyone wants to mount a round-trip mission, pretty much all the landers will have to be Mars orbit rendezvous types. Otherwise you're adding a lot of unnecessary propellant and structural mass to the mission that could otherwise be put into useful cargo and habitat mass.
Quote from: Hyperion5 on 11/09/2013 01:58 amSee the 2:40 mark of the video in the first post. The lander, which clearly masses considerably more than the Apollo Lunar Module, is deploying not one but 3 parachutes. These deploy after the back aeroshell is left behind, allowing the parachutes to unfurl. As the parachutes unfurl the descent engines kick in. I believe Steven Pietrobon mentioned that this approach chops the descent delta-v required from the engines to a mere 500 m/s. That's an impressively low figure for landing something 50 mt or more on Mars. I don't know what the figure would be doing an all-propulsive approach, but it'll be significantly more than that. PAge 19 of this document talks about this.Mars Exploration Entry, Descent and Landing Challenges (paper):http://www.ssdl.gatech.edu/papers/conferencePapers/IEEE-2006-0076.pdf Similarly, a 50 t vehicle requires asupersonic parachute diameter on the order of 90 m. Whileclustered supersonic chutes are an option, the size of suchsystems would still result in large timeline penalties foropening. As such, an all parachute approach for Marshuman exploration vehicles, similar to the concepts nowused for robotic landers, is likely impractical."
I believe the 4.8 km/s of delta-v that site factored in included some 400 m/s of retro-propulsion into it. If you look at the video of the Constellation lander, I think they're doing more than 50 m/s of retro-propulsion. If you upped that to say 400 m/s and let the parachute(s) and aeroshell/heat shield take care of the rest it should work. I don't believe even Curiosity got down to 50 m/s when it fired up its retro-rockets. It was going at least 80 m/s at just around 2 km up when those fired. So it'd be more of a challenge to fire those up earlier, but I think 300-400 m/s of delta-v from the retro-propulsion is very reasonable. Particularly when the alternative is a full 1000 m/s delta-v for a landing done only with retro-propulsion.
Do the engines have to be at or near the bottom of the lander ?What if they were on aerodynamic pylons at the top of the vehicle and therefore above most of the mass so the lander effectively hangs below instead of sitting on the landing engines ? A variant on the Skycrane idea .Mick.
Jeff Foust @jeff_foustMike Gazarik: interested in supersonic retropropulsion for Mars EDL; talking with SpaceX about what they did on F9 1st stage recovery.
Quote from: MickQ on 11/12/2013 08:59 amDo the engines have to be at or near the bottom of the lander ?What if they were on aerodynamic pylons at the top of the vehicle and therefore above most of the mass so the lander effectively hangs below instead of sitting on the landing engines ? A variant on the Skycrane idea .Mick.Well that's a possibility. Lobo and I have mentioned this possibility to Steven Pietrobon, who keeps pointing out these thrusters being angled out will cut their efficiency and thus the lander's payload mass. However, if we're dealing with expendable landers, the delta-v needed to land really isn't that high. Even an all-propulsive landing of a large 100 t lander requires only about a 1000 m/s. Add some parachutes and you can easily cut that to 400 m/s, and 200 m/s if you want to up landed mass even more. I'm not sure of the merits of top-mounted versus side-mounted thrusters, but they should be better at preventing debris damaging the landers during the last phase of the descent. For this reason I prefer descent engines be on the sides or up top and angled out. It might cost some efficiency but it does help with safety. Safety for me is the top priority in any Mars landing.
LMO Earth return 3.4
{snip}Basically, to prevent damage during the landing of a large craft, robotic rovers would be sent in advance to prep a landing pad.
Use a tethered powered landing like MSL did with a staged disposable lander would probably be the cheapest way to do it. Tethered rockets to slow descent and a two staged lander. First stage provides precise powered landing capability and is left behind while the 2nd stage is used for ascent. Also gives the science geeks lots of different systems they have to design so it keeps the NASA boys gainfully employed. Do it the good old fashioned overly complicated American Way!
Because of the amount of debris kicked up during landings, NASA did some research into preparing landing pads. http://www.sciencedaily.com/releases/2012/09/120920101035.htmBasically, to prevent damage during the landing of a large craft, robotic rovers would be sent in advance to prep a landing pad.
Quote from: RonM on 11/30/2013 06:29 pmBecause of the amount of debris kicked up during landings, NASA did some research into preparing landing pads. http://www.sciencedaily.com/releases/2012/09/120920101035.htmBasically, to prevent damage during the landing of a large craft, robotic rovers would be sent in advance to prep a landing pad.Isn't a landing area several km across? Is the entire area going to be stabilized/excavated? If the spacecraft is already moving slow enough to land with precision of a few meters, isn't it already moving slow enough to just land?
Landing anything big (Curiosity size and up) on Mars already requires using rocket engines and the idea is usually to simply use them all the way down to a soft landing at a specific point.
Quote from: eriblo on 12/04/2013 12:18 pmLanding anything big (Curiosity size and up) on Mars already requires using rocket engines and the idea is usually to simply use them all the way down to a soft landing at a specific point.What if you're landing "anything big" that doesn't require soft landing?Random example: food.
Quote from: QuantumG on 12/04/2013 09:21 pmQuote from: eriblo on 12/04/2013 12:18 pmLanding anything big (Curiosity size and up) on Mars already requires using rocket engines and the idea is usually to simply use them all the way down to a soft landing at a specific point.What if you're landing "anything big" that doesn't require soft landing?Random example: food.Speed of sound into a 10 feet of snow?Or speed of sound with some sort of impactor design to keep gees to about constant 100.So tube/pipe which pile drives into surface? absorbing shock both with penetrating groundand payload sliding down tube with ever steeper resistance. So tube being about 5' long.And/or 5 feet of crumple zone- made of stuff which could have value as scrap- metal, plastics, etc.
Quote from: gbaikie on 12/04/2013 11:08 pmQuote from: QuantumG on 12/04/2013 09:21 pmQuote from: eriblo on 12/04/2013 12:18 pmLanding anything big (Curiosity size and up) on Mars already requires using rocket engines and the idea is usually to simply use them all the way down to a soft landing at a specific point.What if you're landing "anything big" that doesn't require soft landing?Random example: food.Speed of sound into a 10 feet of snow?Or speed of sound with some sort of impactor design to keep gees to about constant 100.So tube/pipe which pile drives into surface? absorbing shock both with penetrating groundand payload sliding down tube with ever steeper resistance. So tube being about 5' long.And/or 5 feet of crumple zone- made of stuff which could have value as scrap- metal, plastics, etc.Parachute + airbags should be sufficient for food deliveries to Mars.I remember Jim posted some numbers when people were wondering why NASA didn't send more Spirit/Opportunity missions.
Liken the lander to a Skycrane helicopter, minus rotating parts. The helo can operate by itself or it can carry cargo containers, vehicles or equipment underslung.The lander would be the same. It would contain the crewed area, all propulsion, tankage, avionics and life support. It could be used solely as a crew transport or as a cargo lander. I cannot remember who suggested this idea on another thread but if ISRU is available then the lander can fill up on the surface and launch with all the ascent and descent prop required for the next cycle.Cargo can be hab, power station, ISRU plant, rovers, MPLM type containers, anything that could be made in, or fitted into the same shape and mass limits.Mick.
Parachute + airbags should be sufficient for food deliveries to Mars.
I concede that but it reminds people of the shuttle so we decide to leave it as is. After all, Mars landings will certainly be automated given the need for a 3-6G burn just before touchdown with tight margins. I'm also leaning towards an engines-first descent with the nozzles flush with the heat shield, given the loads the rollover maneuver before would put on structures, and the need to keep the docking port safe. Actually Stanley has just such a concept (which predates mine), "Hydra" Edit: Image uploaded - I was on a mobile device which didn't allow attaching.
Cross sections will be forthcoming, the project is actually more software than a specific vehicle design. You specify the vehicle exterior shape, calculate Newtonian aerodynamics, EDL trajectories, etc. It's meant to be easy for anyone to use. (E.g. A five year old mashing buttons will still result in a functioning spacecraft) You get to choose engine and landing gear configurations, place tanks and habitable volumes, reactors or solar panels, structures, heat shields, etc. All of which effect the center of gravity and trajectories. The core game mechanic is design and analysis rather than real time flying, with crowd sourced subsystems.
Here's my concept "Space Shuttle 2.0" - 10m x 30m - same basic EDL as DRM5, ~100 tons at Mars Entry. The idea is to get a Mars mission (or moon, or asteroid) out of a single SLS launch with in orbit rendezvous of commercially delivered fuel in drop tanks, which makes for a good low cost payload for RLVs, optimized and program survivability rather than IMLEO. The concept artist (Stanley Von Medvey) sketched it launching on FX Heavy though as he's a SpaceX fan. Also shown is an inflatable habitat that could be left in Mars orbit before EDL. At the core of the vehicle is an elevator that doubles as a drilling rig for water for methane ISRU. The legs double as control surfaces similar to hypersonic test vehicles.
And does the artist do commission work? Randy
Quote from: TaylorR137 on 12/17/2013 07:07 amCross sections will be forthcoming, the project is actually more software than a specific vehicle design. You specify the vehicle exterior shape, calculate Newtonian aerodynamics, EDL trajectories, etc. It's meant to be easy for anyone to use. (E.g. A five year old mashing buttons will still result in a functioning spacecraft) You get to choose engine and landing gear configurations, place tanks and habitable volumes, reactors or solar panels, structures, heat shields, etc. All of which effect the center of gravity and trajectories. The core game mechanic is design and analysis rather than real time flying, with crowd sourced subsystems.So, Where can I get a copy of this software?Jason
Here's another piece of concept art, something halfway between Space Shuttle 2.0 and Hydra
Quote from: TaylorR137 on 12/17/2013 09:23 pmHere's another piece of concept art, something halfway between Space Shuttle 2.0 and HydraThat is very cool... The smaller size of this concept looks similar to stretched a F9/FH payload fairing, with similar "legs" as the concept on the earlier stage.
Quote from: RanulfC on 12/17/2013 01:17 pmAnd does the artist do commission work? RandyHe does indeed. http://www.stanleyvonmedvey.comQuote from: JasonAW3 on 12/17/2013 08:22 pmQuote from: TaylorR137 on 12/17/2013 07:07 amCross sections will be forthcoming, the project is actually more software than a specific vehicle design. You specify the vehicle exterior shape, calculate Newtonian aerodynamics, EDL trajectories, etc. It's meant to be easy for anyone to use. (E.g. A five year old mashing buttons will still result in a functioning spacecraft) You get to choose engine and landing gear configurations, place tanks and habitable volumes, reactors or solar panels, structures, heat shields, etc. All of which effect the center of gravity and trajectories. The core game mechanic is design and analysis rather than real time flying, with crowd sourced subsystems.So, Where can I get a copy of this software?JasonIt's not out yet, I'm working on getting the demo functioning then launching a crowdfunding campaign. The software will be free. I'm funding the endeavor by selling custom 3d prints of designs. Hopefully a few of those will end up in wind tunnels!
I've got a few designs I want to test out, including a blended wing in body lifting body hybrid I want to test out.Does it handle wind tunnel testing?Jason
Aim your orbital mirrors at relatively unstable solid carbon dioxide in the area you intend to land; immediately before your land there. Transient localized increase in atmospheric pressure will increase drag and downmass. Feel free to take that one @boredelonmusk!