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Michael Bloxham
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« Reply #270 on: 12/19/2010 10:05 AM » |
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Final IMLEO required for each "piece" should be ~60 tonnes. So potentially could be flown as a "dual-manifest" on Falcon X Heavy or SLS (both are 120 tonnes plus). Which is an interesting way to overcome the restrictive PLF diameter in and of itself. Otherwise, six launchers with a more moderate ~60 tonne capacity could be used - potentially cheaper but more difficult to assure all the pieces make it to orbit before the launch window closes.
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Michael Bloxham
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« Reply #271 on: 12/19/2010 12:05 PM » |
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If assuming 3 nominal surface missions with return, remaining assets which might be re-used towards the construction of the first base include:
6x MABs ("MobileHabs")
3x ASHs ("MobileLabs")
3x ISRU "Trucks" (sans Ascent Vehicle)
If assuming all of these assets are able to be remotely driven to the base site (which should be likely given their multiple- redundant motive components; wheels, motors, solar arrays, etc. and general robustness shared with the mobile habs), then this should result in:
- 9x 50m^3 = 450m^3 of useable living volume.
- 12x 188m^2 solar array area = 2256m^2 = 45kW of *average* power (~135kW peak!).
- (9x ~6m^3) + (3x ~14m^3) = ~96m^3 of insulated tank volume.
Plus at least 2 MABs - which can be used as long-range exploration vehicles - and one ISRU/MAV from the incoming crew rotation.
A bulk-cargo variant of the MAB design (with pressure vessel) could also provide about 3.5 tonnes of various materials to be used for various purposes. Other variations are also possible - such as excavation equipment. Once a perfect spot is picked, perhaps some of the vehicles can have their chassis removed - perhaps just to provide spare parts or perhaps even re-purposed for some other work (such as remotely-driven long-range scouts, etc.).
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MickQ
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« Reply #272 on: 12/20/2010 02:39 AM » |
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If assuming 3 nominal surface missions with return, remaining assets which might be re-used towards the construction of the first base include:
6x MABs ("MobileHabs")
3x ASHs ("MobileLabs")
3x ISRU "Trucks" (sans Ascent Vehicle)
If assuming all of these assets are able to be remotely driven to the base site (which should be likely given their multiple- redundant motive components; wheels, motors, solar arrays, etc. and general robustness shared with the mobile habs), then this should result in:
- 9x 50m^3 = 450m^3 of useable living volume.
- 12x 188m^2 solar array area = 2256m^2 = 45kW of *average* power (~135kW peak!).
- (9x ~6m^3) + (3x ~14m^3) = ~96m^3 of insulated tank volume.
Plus at least 2 MABs - which can be used as long-range exploration vehicles - and one ISRU/MAV from the incoming crew rotation.
A bulk-cargo variant of the MAB design (with pressure vessel) could also provide about 3.5 tonnes of various materials to be used for various purposes. Other variations are also possible - such as excavation equipment. Once a perfect spot is picked, perhaps some of the vehicles can have their chassis removed - perhaps just to provide spare parts or perhaps even re-purposed for some other work (such as remotely-driven long-range scouts, etc.).
Mike. Once the perfect spot is picked and the base starts taking shape, would it be usefull to have a Hab Hub to connect the pieces together ? As an example, 6mt diameter with six or eight locks around the perimeter at which any mobile vehicle can dock or any with the chassis removed can be permanently situated. One or two could be for ISRU units which could be easily un-docked and replaced as new and improved vehicles arrive on subsequent missions. The locks should all be identical so any vehicle could use any port. I know it's a bit further off than your current plans but it is another idea to put in the box. Mick.
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Michael Bloxham
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« Reply #273 on: 12/20/2010 02:52 AM » |
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Yeah I was just thinking about this. Perhaps such dedicated 'hubs' would work best - *without* solar arrays - so that they maintained spacing between Mabs (which would constitute the end modules) and the ASH's (which would constitute the "halls") so that the solar arrays do not overlap? (Otherwise, perhaps the solar arrays could be detached from each vehicle and laid out on the nearby ground?) Such 'hubs' could be packed with consumables and other supplies - thereby effectively functioning as the 'bulk cargo' vehicle. So every time a new supply drop was made another hub would be left behind to facilitate base expansion.
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A_M_Swallow
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« Reply #274 on: 12/20/2010 05:09 AM » |
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It may be possible to move a hub without solar arrays by towing it. A single towing or tractor mobile could be shared between several habs if the habs are only moved occasionally.
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Robotbeat
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« Reply #275 on: 12/20/2010 06:23 AM » |
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Sorry, I mis-read your original post. That's an interesting idea, Mick. I'll have to have a think about potential applications.
Changing subject, here is a post I made at the yahoo groups forum that I thought I'd share here also - as I know a lot of you guys here at NSF are quite creative when it comes to this sort of stuff:
*******
Hey guys.
I'm running into some interesting design decisions for MP4 - and I need your input:
1: As mentioned in reply to Harolds queries: the volume required for seed hydrogen storage is very large; too large to be accomodated on the ASH if a decent amount of interior room is to be left over. So I've reverted back to the previous baseline of having all ISRU needs provided by the ISRU/MAV lander. This would require an additional critical surface-rendezvous of the ASH lander with the ISRU/MAV lander, or alternatively the ISRU/MAV could land with an additional large array (to bump its total array area from ~190m^2 to ~380m^2, which is what is required to consume the seed hydrogen within 60 days or so). Such an additional array would mass at least 500kg. Which is the better solution?
...
In my opinion, the better solution is to go with carbon monoxide instead (can be used for fuel cells as well as for fuel for a rocket), except for possibly some seed hydrogen for water production for crew use, unless that is just going to be brought along with.
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MickQ
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« Reply #276 on: 12/21/2010 04:14 AM » |
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More on the Hub idea.
Even if not being used as a base, as such, it would still be a place for MABs to meet for exchange of supplies, samples, equipment etc without having to suit up and do multiple airlock cycles. With one or more ISRU units attached it would be essentially a supply depot and somewhere to sit back and ride out a major dust storm or deal with a medical situation or just somewhere to enjoy a bit of time outside the restrictions of suits and rovers.
One problem I see is that the ISRU/MAV would un-dock and move away when the crew leaves. Launch would essentially destroy the ISRU plant, right ? Mike, could the ISRU unit be left attached to the hub and detached from the chassis thus leaving the MAV to move to a safe distance before the crew lifts off ?
Mick.
Mick.
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Michael Bloxham
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« Reply #277 on: 12/21/2010 06:06 AM » |
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That is a good question that I haven't been able to put a lot of thought into. I see that you envision the "hub" having quite a large internal volume - perhaps larger than the other vehicles? I was envisioning a "hub" consisting of the same-sized pressure vessel used for the MABs, ASHs, and ERVs (50m^3, 3.4m diameter tube) - to keep commonality and minimize development expense. If the large fold-out solar array is left out (necessitating that the vehicle is 'towed' as A_M_Swallow suggests) then the resulting spacing could ensure that the solar arrays on the other vehicles do not intefere with each other. I do not envision such "hubs" being used to support initial exploration missions - as this is what the ASH or "mobile lab" vehicles are for. The idea of bringing the ISRU unit along with you is an interesting one, however.
The issue of launch method for the MAV is an interesting one also. As I see it, there are two potential options:
1: To have the ascent vehicle launch straight from the ISRU vehicle (as in the current baseline); through an opening in the 'canopy' created by the removal (or simply retraction) of the center solar array 'petal'.
2: Allow the ability for the ISRU vehicle to detach itself from the ascent vehicle, probably through the use of deployable legs on the ascent vehicle, once deployed from which the ISRU vehicle can drive out from underneath - giving a fair amount of distance from the launch location.
No1 is mechanically tricky but it would allow for the lightest-possible ascent vehicle. Leveling is provided by the ISRU vehicles active suspension system (which I assume would be a characteristic of all the mobile vehicles in the architecture). The mass of the fully-fueled ascent vehicle is only ~13 tonnes so should not require much thrust to attain lift-off in Mars' low gravity. The real damage potential probably comes from the debris cloud that is kicked up and thrown around the vehicle - potentially sand-blasting components and damaging the solar arrays from underneath moreso than on top.
No2 would appear to be the more sensible choice - but the launch 'legs' required would result in a slightly heavier and more complex ascent vehicle - especially if these 'legs' are to be left behind on the surface. This option also eliminates the possibility of a strategic "hold-down" period to test the engines before lift-off. (Although this makes me wonder whether or how this function may be achieved in the first place?)
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MickQ
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« Reply #278 on: 12/21/2010 07:32 AM » |
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Yeah Mike.
I think we have crossed wires. I was thinking a 'Tuna Can' style round pressurised space of 5 - 6 mt diameter with a number of locks around the perimeter. Not, as you say, for initial exploration but further down the track when a site has been chosen for some sort of fixed installation.
Re the ISRU/MAV. If the solar panels are the only items likely to be damaged at launch then maybe they could be removed and the vehicle driven on battery power to the launch site and after launch at some future stage the panels re-attached. I just have a thing about wasting a viable on-site asset if it can be used in the future.
Mick.
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Michael Bloxham
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« Reply #279 on: 12/21/2010 08:39 AM » |
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I think we have crossed wires. I was thinking a 'Tuna Can' style round pressurised space of 5 - 6 mt diameter with a number of locks around the perimeter. Not, as you say, for initial exploration but further down the track when a site has been chosen for some sort of fixed installation.
Right. I guess such a cylindrical hub makes sense. However, at 6m diameter (about the limit of what can be accomodated inside the standard 9m diameter base aeroshell if you consider that the descent stage must be fitted underneath instead of at the sides) the habitable area is no more than that of a MAB or ASH. Also, there would be no room for wheels, etc. so that it could be towed. I think it would make more sense to just add some additional docking ports to an ASH and call it a hub. ;-) Re the ISRU/MAV. If the solar panels are the only items likely to be damaged at launch then maybe they could be removed and the vehicle driven on battery power to the launch site and after launch at some future stage the panels re-attached. I just have a thing about wasting a viable on-site asset if it can be used in the future.
Mick.
Yes, I like this idea. Designing the solar arrays so that they are removable - for all the vehicles in the architecture - would allow more versatility of base configurations (when it comes to that stage) also. However, what would be the best method to allow this? Perhaps the arrays could be re-furled before being de-mated from the vehicle and finally removed via some sort of cable system?
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Kaputnik
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« Reply #280 on: 12/21/2010 09:05 AM » |
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What sort of voltage would the PVA system operate at? Lower voltages mean more losses if you are talking about operating via a cable system.
I suppose you could ramp up the voltage with a transformer but it's all extra mass.
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Michael Bloxham
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« Reply #281 on: 12/21/2010 09:30 AM » |
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Sorry, I meant "cable system" as a means to remove the arrays from the roofs of the vehicles. I was thinking they could be slid off and rotated down to the ground using nothing more than a few cables. The alternative would be a ~1 tonne crane.
Re: PVA voltage: I imagine it would be sensible to have integral transformers to boost power to at least 36 or more volts for internal power use inside each of the vehicles in the first place. What is the general standard for spacecraft? In any case additional transformers would probably be required to allow transmission to high-power processes that would inevitably be used in such an initial base (e.g. baking bricks, metallurgy, etc.).
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Michael Bloxham
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« Reply #282 on: 12/21/2010 06:32 PM » |
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With all the excitement around SpaceX lately, I thought it would be interesting to contemplate the capabilities of their Falcon 9 Heavy with respect to mars missions.
Apparently, if assuming a PLF diameter of just under double the core diameter (which seems to be about the maximum that has been achieved for other launch vehicles in the past), and also assuming that the payload *is* the fairing (i.e. the backshell doubles as the LVs aerodynamic nosecone) then a conventional mars-entry vehicle with a heatshield diameter of about 7.2m could be achieved. That would allow about 5 tonnes surface payload - perfectly suited to the Falcon 9 Heavy's ~30 tonne IMLEO capability.
Which got me thinking: Could a viable humans-to-mars architecture be built around such a small surface payload capacity?
Perhaps it could be possible if the mission mode is reverted back to a more conventional fixed-hab + rovers architecture - whereby the base assets are assembled before the crew arrive.
The ISRU/MAV vehicle could be split into two half-sized ISRU (and still mobile) vehicles: One to produce propellant for the ascent, and one to produce all of the water and oxygen needed for the surface stay.
The basic shell of a "Sundancer"-sized inflatable living module could possibly fit into a single 5-tonne lander - though without the mobility system the base would have to be constructed around wherever this component happens to land.
The mobile habs could possibly be squeezed down further - if initial consumables loading is kept to an absolute minimum (only a week or two of supplies upon landing, for example, before requiring resupply from the surface assets). And if capabilities (speed, range, duration, etc.) are also reduced - finally turning what started out as a mobile hab into a small medium-duration rover.
And the ERVs could be whittled down to the size necessary to fit within a single F9H launch if their TEI stage is launched and aerocaptured separately into Mars' orbit.
Interior volume for both the outbound and inbound legs would be very restrictive, however, at only ~30m^3 per vehicle, or ~15m^3 per crew member.
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Michael Bloxham
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« Reply #283 on: 12/21/2010 06:45 PM » |
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So perhaps the launch manifest for such an architecture might look something like this:
ISRU1/MAV (produces fuel for integral ascent vehicle)
ISRU2 (produces water and oxygen for entire surface stay)
FAB (Sundancer-sized ~180m^3 inflatable living volume)
LAB (mobile laboratory which follows Mabs around and used as a "dusty workshop")
MAB1 (downsized mobile hab which resembles a medium-sized pressurized rover)
MAB2 (as above; 2-crew each)
ERV1 (down-sized ERV with integral Dragon re-entry capsule; shown in sketch above)
ERV2 (down-sized ERV with majority of consumables loading)
TEI1 (TEI stage for ERV1)
TEI2 (TEI stage for ERV2)
Total launches of the Falcon 9 Heavy required for each recurring mission = at least 10.
Perhaps the 4800kg or so of food and non-metabolized consumables required for the ~600 day surface stay (for the full crew of 4) could be scattered amongst some of the surface vehicles (as in the current MP4 baseline), or perhaps delivered separately on a dedicated cargo lander (or two?).
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Robotbeat
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« Reply #284 on: 12/21/2010 06:58 PM » |
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Yes, I really like the idea of AtlasVHeavy/Falcon9Heavy for a Mars architecture. You could land all the parts needed... A dry Mars Ascent Vehicle, a pressurized lander or two, inflatable hab modules, power/ISRU module, bulk supplies, etc. (Some things will need to be landed more gently than others.)
It could be done. Not easy, but nothing is easy in space (except docking... we seem to do that all the time on ISS... just saying that for mission planners out there).
By the way, I think there's a good argument to be made to put a small GPS constellation around Mars, as well as precision mapping of the surface, to allow precision landing without all the uncertainty we have now. And for a base, a prepared surface would help. I wonder if there's anything on Mars like the dry lakebeds or Kazakh steppes on Earth which are really flat and nice for landing on?
Also, some more research on supersonic parachute deployment (i.e. getting the parachute or a drogue to deploy at, say, Mach 2.5 or 3 instead of the current 1.8) and stability (currently, MSL will do active stability control with RCS jets to cancel any wild oscillations that might occur while supersonic under the parachute) would allow more mass to be landed for a given heat shield size. The more robotic missions we do to Mars, the more we learn about Martian EDL, so the less uncertainty and the more payload we can land for a given IMLEO.
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