A new thread for discussing Mars EDL technologies and especially how they might impact the choice of architecture, launchers and in-space transportation.
Quote from: mmeijeri on 08/16/2009 10:27 pmA new thread for discussing Mars EDL technologies and especially how they might impact the choice of architecture, launchers and in-space transportation.Since we can do 2.5 tonne chunks already with viking technology then lets just land stuff on mars in 2.5 tonne chunks. Lots of launches but mass produced entry shells help lower costs.Transit habitat can be bigger since it doesn't land. Crew lands in rover to take them to inflatable habitat, spare rover, greenhouse, etc all landed in 2.5 tonnes chunks. (actually 2.5 tonnes at entry interface so ~1.5 tonnes payload.)
There are strong arguments either way, but IMHO we have the opportunity to develop an SDLV today that could easily give us 12m+ PLFs, and that seems to be just about on the cusp of allowing us to land big enough payloads to support a manned mission- especially if a lifting entry is used, increasing the above numbers.
Quote from: Nathan on 08/22/2009 12:33 pmQuote from: mmeijeri on 08/16/2009 10:27 pmA new thread for discussing Mars EDL technologies and especially how they might impact the choice of architecture, launchers and in-space transportation.Since we can do 2.5 tonne chunks already with viking technology then lets just land stuff on mars in 2.5 tonne chunks. Lots of launches but mass produced entry shells help lower costs.Transit habitat can be bigger since it doesn't land. Crew lands in rover to take them to inflatable habitat, spare rover, greenhouse, etc all landed in 2.5 tonnes chunks. (actually 2.5 tonnes at entry interface so ~1.5 tonnes payload.)2.5mt is not enough as the smallest chunk. But still, if you really want to go with the smallest possible piece to land on Mars, use the current upper boundary with (enhanced) Viking technology heatshields. That's about 3-4mt at 5.5m (Ariane 5) and maybe about 5mt with a potential Delta IV Heavy hammerhead 6-7m fairing.
Quote from: Nathan on 08/22/2009 12:33 pmQuote from: mmeijeri on 08/16/2009 10:27 pmA new thread for discussing Mars EDL technologies and especially how they might impact the choice of architecture, launchers and in-space transportation.Since we can do 2.5 tonne chunks already with viking technology then lets just land stuff on mars in 2.5 tonne chunks. Lots of launches but mass produced entry shells help lower costs.Transit habitat can be bigger since it doesn't land. Crew lands in rover to take them to inflatable habitat, spare rover, greenhouse, etc all landed in 2.5 tonnes chunks. (actually 2.5 tonnes at entry interface so ~1.5 tonnes payload.)2.5mt is not enough as the smallest chunk.
Quote from: simon-th on 08/22/2009 12:45 pmQuote from: Nathan on 08/22/2009 12:33 pmQuote from: mmeijeri on 08/16/2009 10:27 pmA new thread for discussing Mars EDL technologies and especially how they might impact the choice of architecture, launchers and in-space transportation.Since we can do 2.5 tonne chunks already with viking technology then lets just land stuff on mars in 2.5 tonne chunks. Lots of launches but mass produced entry shells help lower costs.Transit habitat can be bigger since it doesn't land. Crew lands in rover to take them to inflatable habitat, spare rover, greenhouse, etc all landed in 2.5 tonnes chunks. (actually 2.5 tonnes at entry interface so ~1.5 tonnes payload.)2.5mt is not enough as the smallest chunk. .. because ?
I get why he says that. It's tight. 2.5tonnes leads to ~1tonne on the surface. People weigh 100kgs each, space suit and food for say 30 days ~150kgs.Leaves 750kgs for pressurised rover.
Quote from: Nathan on 08/25/2009 09:11 amI get why he says that. It's tight. 2.5tonnes leads to ~1tonne on the surface. People weigh 100kgs each, space suit and food for say 30 days ~150kgs.Leaves 750kgs for pressurised rover. So, your proposal is to encapsule each Mars surface mission crew member separately in a rover and without a spacesuit (estimate about 250kg for crew person + spacesuit and other individual life support equipment), 15kg per day per person in provisions. That says you can't do it in 2.5mt chunks - even if those chunks were the net payload to the Martian surface because A. you will get all your crew members to the Martian surface in one piece and B. your pressurized rover is going to weight a lot more than 750kg (the power source alone, e.g. RTGs for the rover will weight more than that).
Crew member including spacesuit & food. =250kg. It takes far less than 15kg per day per person. 2.5kg max. So that's 20 days of food.
Rover would use solar power not rtg.
Apollo LRV had a mass of 210kg. Add thin pressurised enclosure and solar panels (batteries already included but become rechargeable). As mentioned one may be able to use the entry mass of the upper aeroshell as part of the rover hull? Alternatively just use steel or kevlar.No airlock. Whole rover depressurises.
Quote from: Nathan on 08/25/2009 10:35 amCrew member including spacesuit & food. =250kg. It takes far less than 15kg per day per person. 2.5kg max. So that's 20 days of food.No. We know from the ISS that you have to calculate about 15kg per day per person - with water recycling that goes down, but obviously your simple Mars rover won't have that.250kg is for the crew member + spacesuit + individual life support equipment.QuoteRover would use solar power not rtg.That doesn't work. The solar cell area you require for a pressurized rover (about 5-10kWe constant) is much too high to attach to a rover. All studies have RTGs for rovers as front runners with rechargeable/re-fuelable pressurized rovers as a second alternative (rover gets fueled/charged at base, goes for a ride, comes back and gets fueled/charged again - from an immobile station).P.S. RTGs are actually the most mass efficient way to power a rover - batteries or fuel cells or the in-workable (from an area perspective) solar cells are more massive. Quote Apollo LRV had a mass of 210kg. Add thin pressurised enclosure and solar panels (batteries already included but become rechargeable). As mentioned one may be able to use the entry mass of the upper aeroshell as part of the rover hull? Alternatively just use steel or kevlar.No airlock. Whole rover depressurises.Those are all non-workable ideas. All pressurized rover designs mass way above the Apollo LRV. We are talking several mt here, even without an airlock.For a simple overview of a 20-day autonomous 2-crew Mars rover design proposal from 1997 look here: http://www.astronautix.com/craft/drmrized.htm. It clocks in at 16.5mt. The best suitable power source with 1.1mt are RTGs, the photo-voltaic alternative would mass 2.8mt and require an area of 1300m² at 66m³ packaging.
Ok so need a bigger chunk? Life support may be big issue then- depends on how easy water recycling can be. Urine processing and air dehumidification is thus a must. I guess with the rover I am think of something along the lines of the 1.4tonne rover from Zubrin's Case for Mars book only lighter, slower, less capable. Something between Apollo LRV and the Zubrin rover. The rover you are referencing is for long duration missions of 500km range. I'm only needing for running about the landing site area ~ten k on so.
Again one needs to consider how basic the rover can be. It's a tent with wheels. Hell, Spacesuit technology could provide life support.
QuoteRover would use solar power not rtg.That doesn't work. The solar cell area you require for a pressurized rover (about 5-10kWe constant) is much too high to attach to a rover.