Author Topic: Manned Mars Lander  (Read 63527 times)

Offline Lobo

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Re: Manned Mars Lander
« Reply #20 on: 11/10/2013 06:14 am »

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. 


Hmmm?
This whole concept I'm kicking around is a direct ascent lander.  And a Direct landing landing lander. 
Mars Direct, but with both of Zubrin's landers combined into a single bigger lander.  A double sized version of Zubrin's ERV basically.  Zubrin was working with a SDHLV with a much smaller capacity than FXH might have.  So putting everyone in the ERV and sending them to Mars in a single vehicle would make things pretty cramped for the trip out and the surface stay.  Zubrin only had them in it for the trip home.  Plus it would land with very little equipment and provisions.  But...with the potential of a an LV in the 200-300mt range (our speculation) Than that ERV and be scaled up.  A Larger hab capable of adequately sustaining the crew for the trip out and the surface stay as well as the trip home.  Enough cargo room for at least some modest equipment for the surface mission.  Some small rovers, solar arrays, and inflatable surface habs, etc. 


http://www.angelfire.com/md/dmdventures/orbitalmech/DeltaV.htm

From   To   Delta-V (km/s)
LEO   Mars Surface   4.8
LEO   Lunar surface   6.2
Mars   LMO   4.4
LMO   Mars    0.05
LMO   Earth return   3.4
Lunar surface LEO 3.2


Total 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.

You could have a variant of this lander that was a cargo hauler.  Remove the hab area to lighten it up for more cargo mass.  And remove the mass of the LH2 and it's tank as this lander won't be lifting off again, so no need to generate more fuel on the surface.  Everything about EDL would be the same, and the same launch mass and landed mass.  But you are trading extra vehicle mass for cargo mass.

At the end of the day, you are probably right...  The penalties are probably too big to be able to have a single common vehicle that can land on mars, take off again, come back to Earth and then land on earth. 
Be pretty cool if could though.

You might still be able to have something like this with MOR.  Like in the paper Oli posted, the DAV.  The Descent Ascent Vehicle.  If it's not coming back to Earth it can have a jettionsable heat shield so it doesn't have to bring it back up.  The engines could be fixed behind it, pointing straight down.
And do a more Mars Semi-Direct type of architecture.

Offline Hyperion5

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Re: Manned Mars Lander
« Reply #21 on: 11/10/2013 07:59 am »

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. 


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 a
supersonic parachute diameter on the order of 90 m. While
clustered supersonic chutes are an option, the size of such
systems would still result in large timeline penalties for
opening. As such, an all parachute approach for Mars
human exploration vehicles, similar to the concepts now
used 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. 

Offline Lobo

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Re: Manned Mars Lander
« Reply #22 on: 11/11/2013 05:31 pm »

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.

Perhaps a better way to approach it is more like the biconic shapes that have been the favorite for NASA DRM's, as well as Zubrin's Mars Direct for the ERV.

Something like the DC-X/Y.  Then your engines are fixed downward without the need to deploy anything, other than landing legs.  Might be better to have tall, more slender propellant tanks running through the center of the vehicle though, rather than just two tank on top of each other. IN this way, your center of gravity is all at the bottom when doing terminal descent, rather than having the mass of the LOX or CH4 up the bottom of a higher tank.  Kind of like how Boeing's Lunar and Mars methalox lander had slender vertical tanks.  Then you could have your cargo deck down low around the tank cluster in the center, so that they are near the surface for ease of deployment. 

It does present some challenges of reorientation in a supersonic slipstream to get the engines down and then get them lit.  I think the blunt body like the SuperRedDragon is a safer design in certain respects. (No supersonic orientation, no firing of rockets into a supersonic slip stream, not as tall) But it might just not be feasible to make that shape do everything.  (it might not be feasible to make -any- shape do everything actually).

Edit:  I Borrowed the picture that Lars Posted here for this.  Different tread but it made me look at it for a Mars lander.

http://forum.nasaspaceflight.com/index.php?topic=32180.msg1118725#msg1118725
« Last Edit: 11/11/2013 10:03 pm by Lobo »

Online MickQ

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Re: Manned Mars Lander
« Reply #23 on: 11/12/2013 08:59 am »
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.

Offline Hyperion5

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Re: Manned Mars Lander
« Reply #24 on: 11/15/2013 02:14 am »
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.

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. 

Offline Elmar Moelzer

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Re: Manned Mars Lander
« Reply #25 on: 11/15/2013 04:56 pm »
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.
Maybe an aerospike/plug like arrangement as they had envisioned for the ATV VTOL?

Offline docmordrid

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Re: Manned Mars Lander
« Reply #26 on: 11/18/2013 01:43 am »
Jeff Foust tweeting from the "The Path toward Humans to Mars" presser.

Quote
Jeff Foust ‏@jeff_foust
Mike Gazarik: interested in supersonic retropropulsion for Mars EDL; talking with SpaceX about what they did on F9 1st stage recovery.
DM

Online MickQ

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Re: Manned Mars Lander
« Reply #27 on: 11/18/2013 07:23 am »
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.

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.

My thinking is that you have the engines mounted on the MAV which sits atop what is effectively just a cargo container with a heat shield.  The MAV has all the propulsion, descent/ascent engines and OMS in modules mounted on pylons above the majority of the mass of the descending craft so gravity helps with stability.  Gimbal and/or throttle the engines for orientation and steering. Maybe flaps on the pylons could help here as we'll.

Having the engines 5, 6 or more meters above the ground would, as H5 says, reduce or eliminate blown debris damage to the cargo section.  When ready to leave, the MAV lifts off the top leaving the lower cargo unit un-damaged by rocket plumes.  This way the MAV section could be refuelled in orbit and re-used.

I'm just not sure if the MAV should house all the tankage or if descent prop should be carried in the lower section.

Thoughts ?

Mick.

Online MickQ

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Re: Manned Mars Lander
« Reply #28 on: 11/20/2013 07:49 am »
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.

Offline MikeAtkinson

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Re: Manned Mars Lander
« Reply #29 on: 11/20/2013 08:09 am »
LMO   Earth return   3.4

Should be:

LMO   Earth return   2.3

assuming aero-braking into LEO (or direct landing), see http://en.wikipedia.org/wiki/Delta-v_budget.

Offline adrianwyard

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Re: Manned Mars Lander
« Reply #30 on: 11/27/2013 10:17 pm »
Why is Heavy EDL on Mars so hard?

The following is an attempt to wrap my head around why high-mass EDL is so difficult on Mars - it leads me to some out-of-the-box ideas, There’s a good chance I’m making some false assumptions, and would appreciate any corrections and/or feedback!

The Main Challenges:

1] At high speed (orbital/interplanetary), the Martian atmosphere is thick enough to cause significant heating.
2] At low speed, it’s not thick enough to provide significant drag or lift. (~1% of Earth sea level)
3] Gravity is 1/3 of Earth, so free-fall acceleration is quite high.
4] Parachutes are problematic for several reasons:
4a] Unlike Earth-based chutes they need to be deployed supersonically because the craft is still going that fast when close to the ground.
4b] Large diameter supersonic parachutes are untested beyond Viking-scale. Deployment times and inflation dynamics of large chutes in a supersonic airstream are big risk factors.

So it seems from an EDL point of view Mars is the worst of all worlds.

While parachutes are problematic deployable rigid aerosurfaces might be of use at high-speeds - when large supersonic parachutes are risky. It seems there should be a period where the dynamic-pressure and heating have lessened to the point that rigid surfaces can be deployed, and yet the pressure is high enough that they'd provide significant lift and/or cross-range. Like a parachute, ballute, or hypercone, they lessen the ballistic coefficient of the system, and the additional lift/drag can be used to burn off groundspeed.

See below for a depiction of one application of this idea (Fig 1: Biconic-Fins). I’ve taken the 10m x 30m biconic aeroshell from DRA 5.0, flattened the bottom windward surface, and added two small long fins. I’m assuming that the initial entry heating will be too high for the fins and so they are initially stowed, hidden in the shock wake. (Fig 2: Fins-Stowed ).

At high speed, once the fins are deployed, this may well ‘fly’ as a lifting body (Fig 3: Fins-Horizontal). Control surfaces on the trailing edges of the fins could be used for directional control (a la ESA’s IXV), but as speed drops, it would need to flare to an ever more extreme pitch angle. This is fine as the goal is to lose ground speed. Also, the momentum of the vehicle in relation to the thin air should allow for control to be maintained.

At lower speeds, I wonder if it would be beneficial to angle the fins down to trap the thinning air, acting a little like a rigid parachute (remember the nose is pointing upwards, but the heat shield on the bottom of the vehicle is facing 'down' with respect to the airstream). (Fig 4: Rigid-Chute)

At some point the vehicle stalls when near vertical (hopefully with a lowish ground speed and near the surface) and it’s time to eject the upper fairing, and release the lander, which nulls the remaining sideways velocity and performs a propulsive landing.

Of course, the fins and changes to the aeroshell add mass, but depicted on the pad it looks relatively slight (Fig 5: On-Pad). The question is if they offer any net benefit in terms of final descent rate and groundspeed when the lander deploys.

If there is any net benefit to adding the mass of these aerosurfaces, then we can play with a couple of variables: the fins can be made larger, and more radically, the aeroshell can be extended down the length of the exterior of the Earth Departure Stage, forming what is essentially a sail. (Fig 6: Larger-Fins, Fig 7: Stretched-Over-EDS.)

Issues and Questions:
1] Do the fins need to be deployed at all? Can they be fixed, and survive the max heating?
2] If not, how are the fins deployed? If skip entry is used, it could be done during the skip, or the vehicle oriented nose-forward temporarily to lessen the forces.
3] RCS: It’s a good guess the DRA 5.0 aeroshell had a beefy RCS. That will be needed here too.
4] Q: How was the biconic aeroshell in DRA 5.0 supposed to be steered? Just RCS?
5] Center of mass will need to be controlled, and strong roll authority required to prevent it rolling onto its side or back - as was the case with DRA 5.0 design. The fins will automatically correct the orientation when in a skyward pointing dihedral configuration, but not when at the anhedral 'parachute' angle. The elevons on the fin trailing edges would be needed in this case.

My goal is to determine if there is any 'low hanging fruit' to be had in terms of tacking on small aerosurfaces to existing designs, with minimal additional mass and complexity. If there is some benefit to be had, then it may be better to design low density lifting bodies from scratch.

To be clear, there’s no mathematical modeling behind any of this, just basic physics knowledge and intuition. I welcome any comments.
« Last Edit: 04/10/2014 12:18 am by adrianwyard »

Offline adrianwyard

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Re: Manned Mars Lander
« Reply #31 on: 11/28/2013 01:18 am »
I just found the following very interesting paper from 2009. In short, it looks like a 10m diameter blunt body design can land more mass than the 10m x 30m shape used in DRA 5. Unexpected!

Even though a DRA 5 style biconic presents an area to the airstream that's >3 times larger than a 10m blunt body, it's apparently much less draggy. Adding fins and flattening the base would definitely help that, but only if the nose was pitched up wrt the airstream... 

http://www.ssdl.gatech.edu/papers/conferencePapers/AIAA-2009-6684.pdf
« Last Edit: 11/28/2013 05:03 pm by adrianwyard »

Offline adrianwyard

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Re: Manned Mars Lander
« Reply #32 on: 11/28/2013 05:28 am »
Continuing on from my previous post on deployable rigid heat shields/aerosurfaces:

Most depictions of Mars landers show comparatively large heat shield diameters - as expected for the thin atmosphere. But only a few have shown deployable structures. I wonder why. Perhaps the complexity of the deploy mechanism adds more mass than you gain back?

Some versions of Zubrin's Mars Direct lander have used an umbrella-like 23m fabric shield, or unfolding, overlapping petals as shown at 0:58 in the following video. It appears to deploy to around 14m.


For fun, I’ve mocked up what a 5m heat shield would look like on a SpaceX Dragon (Red Dragon with Super Dracos). It would need a fairing with the same geometry as that used on the 5m Falcon 9. See Fig 1: "5m-fairing", below.

But rather than just ejecting that upper fairing, it could be kept as heat shield extension panels. See Fig 2: “extensions”. The blue panels are raised slightly to preserve the slight pitch angle (and therefore lift and steering) along the same axis as the regular Dragon.

The total heat shield area is now approx. three times that of the stock 3.7m Dragon (34.6 sq.m vs 11 sq.m). The difference can be seen in Fig 3. The view from below is depicted in Fig 4.

The resulting star shapes are unusual, but the edges are curved away from the airstream, and need not be sharp, so I’m guessing they could withstand the heating…

It is hoped that a Falcon Heavy will throw ~10 mt to Mars, which would allow a Red Dragon to bring ~1 t to the surface. The question is: will carrying the extra weight of a 5m extensible heat shield ultimately allow more than 1 t to be delivered to the surface? Note that in this “Red Dragon 2” version the heat shield is released when retropropulsion starts (~10sec before touchdown), so the actual vehicle mass to be decelerated is less than with the standard Red Dragon concept. Also, the payload can be slung underneath rather than inside the Dragon - good for rovers.

If it turns out that increasing the area provides a net gain, then a larger fairing/panels can be used. Fig 5: big-fairing.

Comments and corrections welcome...

Note: the idea of using a detachable larger heat shield was first discussed in the Red Dragon thread last year:
http://forum.nasaspaceflight.com/index.php?topic=26269.msg931942#msg931942
« Last Edit: 11/28/2013 04:22 pm by adrianwyard »

Offline cordwainer

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Re: Manned Mars Lander
« Reply #33 on: 11/29/2013 01:08 am »
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!

Offline adrianwyard

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Re: Manned Mars Lander
« Reply #34 on: 11/29/2013 07:29 pm »
More numbers on the Dragon mockup: A 5m heat shield with the upper fairing retained as extensions gives the equivalent area of a 6.6m diameter circular shield. The area opened up between the Dragon and the heat shield is 1.2m high, so tall enough to fit something Curiosity-sized but not with any ground clearance.

Offline Hanelyp

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Offline adrianwyard

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Re: Manned Mars Lander
« Reply #36 on: 11/30/2013 06:03 pm »
Absolutely, hypercones et al do look very promising. Here's a variant that extends a rigid aeroshell, and might be more appropriate for a minimal enhancement to Red Dragon:

http://www.nasa.gov/mission_pages/tdm/ldsd/index.html#.UpoxjZE6G2k

You could use it to extend SpaceX's current 3.7m shield, or to replace the fairing/shield panels that extend beyond the 5m one depicted above. Although, since the extensions in my mockup are also the fairing, they come for almost no mass penalty.

I wonder if inflatable technology could be applied to the huge (10m x 30m) biconic in DRA 5.

I think there are two classes of problem here: 1] how to get more than 1 mt to Mars (current limit) at all, even if it's just 3-5 mt. 2] how to land really huge, really heavy things that would be needed for a human mission - the sort of lander depicted in the video at the beginning of this thread.


Offline RonM

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Re: Manned Mars Lander
« Reply #37 on: 11/30/2013 06:29 pm »
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.htm

Basically, to prevent damage during the landing of a large craft, robotic rovers would be sent in advance to prep a landing pad.

Offline A_M_Swallow

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Re: Manned Mars Lander
« Reply #38 on: 12/01/2013 03:53 am »
{snip}
Basically, to prevent damage during the landing of a large craft, robotic rovers would be sent in advance to prep a landing pad.


If the same rover can prepare the land for the habitat and ISRU equipment then the robotic rover may be worthwhile.

Offline Lobo

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Re: Manned Mars Lander
« Reply #39 on: 12/03/2013 04:49 pm »
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!

There's a concept I saw on an old Direct paper about Jupiter going to Mars.  They had a concept of a biconic aeroshell that opened up into a rigid parachute like decelerator which had retro rockets like the MSL.  The lander itself then lowered down on a tether, and the was softly dropped on the ground, then the aeroshell/rigid parachute flew off for safe ground impact.

The aeroshell basiclly had four petals on the front that opened up at supersonic terminal velocity to help slow the lander down more.  Obviously it would need a certain amount of dV from retro propulsion.  More than if some big soft parachutes were used, but less than if landing a biconic or blunt body shape propusively.

It was a very interesting concept.  However, I'm still of a bit of a mind that just a big blunt body with sufficient retro propulsion is probably the way to go for large payloads.   Like a big scaled up Dragon capsule with the minimum sidewall angle possible for maximum internal volume.  And you compensate for the less mass efficient design by building bigger dumb, cheap rockets to throw the extra mass, and the simplicity of landing something like a big Dragon capsule, and not messing around with giant supersonic parachutes that must be deployed quickly, or biconic designs which could have issues of control coming into the Martian atmosphere (at least I don't think such a design has ever been used for EDL in that way, so there's be a certain development curve.)
Blunt bodies are well understood and tested and can land without needing to jettison the entire biconic.  They can just jettion the heat shield, or not jettison it and just land it like RedDragon.

Now, for a cargo lander, an interesting concept would be to just have a big Dragon like capsule (say 12m diameter at the bottom or so) and then once on the ground, have it open up with petals similar to what Adrianwyard showed above for a large Dragon heat shield.  Except, have that arrangement with the capsule's sidewalls, leaving the payload full open and just sitting on a short platform.  that might be difficult with the rockets in the sidewalls.  If so, then just have one big door in the side that opens into a ramb that the cargo can be offloaded.  For a cargo lander, you don't need the actual pressure vessel inside like the Dragon pressure vessel.  You can just have the unpressurized "shell" with cargo hanger inside.
A hab lander could be the same thing, just with a pressurized hab module inside that shell.   

Have a single large rocket (like MCT) that can launch this Super RedDragon type capsule directly to MArs and through direct EDL.  Common platform, but you can put whatever you want inside.  Land more cargo and hab configurations as necessary.
The only different element needed is a Mars Ascent vehicle. If you were to use inflatable Bigelow modules in cycler oribts, then you MAV can basically just be a standard size Dragon capsule with a propulsion module under it that would launch the crew to a rendezvous trajectory with the cycler for the trip home, and the crew would do Earth EDL in that Dragon capsule once the propulsion module is jettisoned. 
Do the same thing for the trip to Mars.  Launch the crew in a (Red) Dragon Capsule into a rendezvous trajectory with the outbound cycler, and the crew lands in that. 
That can all be done with a man-rated FH, so that the bigger MCT/FX never needs to be man-rated.  It's just a big, dumb, [probably partially reusable] cargo launcher. 
« Last Edit: 12/03/2013 04:50 pm by Lobo »

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