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The "Mars" part of the CEV mission confuses me....
by
Zoomer30
on 27 Jul, 2006 04:52
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I assume they dont expect people to fly all the way to Mars in a CEV, they would need a shrink once they got there. Are they planning some sort of "Mission to Mars" type ship where the CEV is simple used to get to the ship and then land on Earth? I figure a Mini ISS style ship would do the trick. A module for each need (sleeping, eating, exercise, power etc).
I guess the amount of risk involved has me wondering if people going to Mars is worth it. The moon I can see. That is our own backyard. Someday they could be half as many people on the moon as on the Earth (ok perhaps not THAT many).
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#1
by
punkboi
on 27 Jul, 2006 06:36
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Do you read Popular Mechanics? In the December 2005 issue, Buzz Aldrin wrote an interesting article about CEVs being used to transport astronauts to "Cycler" ships that travel to Mars and back. In fact, look up Cycler spacecraft on Google and there are many articles on the vehicles. Didn't really check to see if the CEV is referenced to in those articles as well, though...
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#2
by
mong'
on 27 Jul, 2006 11:36
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given all the design reference missions published by NASA, I also wonder about the necessity of the CEV for a Mars mission, maybe it can act as the entry capsule on the ERV.
anyway the current approach for a mars mission was published in the ESAS report, page 68. it seems they want to use it on a "mars transfer vehicle" that goes to mars and all the way back to earth on its own
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#3
by
Jim
on 27 Jul, 2006 12:00
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Zoomer30 - 27/7/2006 12:39 AM
Are they planning some sort of "Mission to Mars" type ship where the CEV is simple used to get to the ship and then land on Earth?
Yes, it is in the ESAS
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#4
by
PurduesUSAFguy
on 29 Jul, 2006 13:30
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The CEV really wouldn't be any use on a manned mission to Mars other then providing Earth to LEO transport to get to the assembled Mars craft and for rentry. I can't imagine taking the CEV all the way to Mars and back as it would represent ~25tons of dead weight to push into TMI. It would just make more sense to launch the crew and then have the CEV return to earth unmanned and then launch another to pick the crew up upon their return.
(Since all it is providing is Earth to LEO transportation it would make as much sense to use a COTS provider if and when they materialize)
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#5
by
hyper_snyper
on 29 Jul, 2006 13:48
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PurduesUSAFguy - 29/7/2006 9:17 AM
The CEV really wouldn't be any use on a manned mission to Mars other then providing Earth to LEO transport to get to the assembled Mars craft and for rentry. I can't imagine taking the CEV all the way to Mars and back as it would represent ~25tons of dead weight to push into TMI. It would just make more sense to launch the crew and then have the CEV return to earth unmanned and then launch another to pick the crew up upon their return.
(Since all it is providing is Earth to LEO transportation it would make as much sense to use a COTS provider if and when they materialize)
Return from Mars is direct entry. CEV does entry and the MTV goes onto a heliocentric disposal orbit. In order to do what you're saying MTV would have to do EOI, and that takes a lot fuel.
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#6
by
MATTBLAK
on 29 Jul, 2006 14:14
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Zoomer30 - 27/7/2006 3:39 PM
I assume they dont expect people to fly all the way to Mars in a CEV, they would need a shrink once they got there. Are they planning some sort of "Mission to Mars" type ship where the CEV is simple used to get to the ship and then land on Earth? I figure a Mini ISS style ship would do the trick. A module for each need (sleeping, eating, exercise, power etc).
I guess the amount of risk involved has me wondering if people going to Mars is worth it. The moon I can see. That is our own backyard. Someday they could be half as many people on the moon as on the Earth (ok perhaps not THAT many).
Hi, zoomer!! A few months back I published on one of the pages here my idea for a bare-basic Mars mission architecture, including the CEV and derivatives of the LSAM as building blocks. The only (
completely) new elements to be built over the Lunar mission-derived hardware would be the reactor, aero-entry heatshields and ISRU propellant generating package. Basing the architecture on multiple, 'disposable' mission modules, as shown in Apollo and proposed in other mission concepts -- including Russian ones -- would make for a simple(ish) staged approach to manned Mars flights. One of the advantages to this would be minimising the amount of hardware you would have to haul all the way to Mars and back. Also, by using certain modules in a staged fashion for only a few months at a time, you'd minimise the need to build a huge "mothership" that would have to work with PERFECT reliability for the whole 2.5 year or more mission duration.
**************************************************
Also, someone asked earlier; is the CEV going to go to Mars? For a Mars mission architecture, I've looked hard at this question and one of the options, incorporating classical Mars Semi-Direct features, might seem to be thus:
3x launches: 2x Ares V, 1x CEV launcher (EELV or CLV).
LAUNCH #1): HLV with 1x 20-ton Mission Module (crew habitat for outbound flight), 1x 45-ton Mars Habitat-Lander (nearly identical to MM, but attached to upgraded LSAM-derived descent stage. This is for landing and surface Hab only). 1x Earth Departure Stage, which has about 60 tons of propellant leftover from placing MarsHab-Lander & MM in LEO.
LAUNCH #2): Ares V with fully-fuelled EDS (about 120 tons prop.) EDS docks with first EDS, MM & MarsHab-Lander. This is the "Mission Stack".
LAUNCH #3): CEV with crew of 5 or 6 on CEV launcher. CEV docks with Mission Stack and the Stack burns the approx. 180 tons of EDS 1 & 2 propellants (more than twice Apollo quantities) for Trans-Mars Injection .
The CEV functions as the Command & Control center for the outbound journey, as it has a 6-7 month endurance. The MM, packed with consumables and water, acts as the crew's living quarters and "Storm Shelter". The crew sleeps in the CEV for a couple weeks, until the supplies stacked in their MM's sleep cubicles are used up. During the outbound flight, the rear of the CEV gets stacked with the trash and non-recyclables. I estimate that the amount of pressurised living volume available to the crew would be about the same as 4x Shuttle Mid-Decks. Cramped, sure, but do-able. The Mars Habitat/Lander could also be used for habitable volume, if need be (as long as it's Mars surface consumables were left basically untouched). Electrical power for the Mission Stack would come from the CEV & Mission Module's solar arrays (MM uses same array design as CEV).
When the Mission Stack approaches Mars, the crew transfers to the MarsHab-Lander and conducts a direct aero-entry and landing on Mars, next to a pre-landed Mars Cargo-Ascent Vehicle (MCAV). The CEV & MM, their supplies and design life expired, are discarded into solar orbit.
The MCAV has a small 80-to-100kw nuclear reactor that will power its ISRU Ascent Fuel package, and of course the crew's needs for their 18-month stay on Mars. The fuel generation package needs to create more than 30 tons of Lox/Methane for the ascent to orbit. The MCAV also carried to Mars a small Pressurised Rover Vehicle (PRV) for 2-person long distance exploration.
When it's time for the crew to leave Mars, they climb aboard the MCAV. It's Ascent Stage, based on a combined CEV (Crew Module only) and LSAM upper stage, blasts off and rendezvous & docks with a pre-deployed Earth Return Vehicle (ERV). The ERV consists of an (legless) LSAM-based “stretched” descent stage and a standard MM. As on the outbound flight, the MCAV Command Module acts as Command & Control center for the Earth Return flight. After jettisoning the empty MCAV ascent stage, the ERV burns out of Martian orbit for the return home.
**NOTE: For safety and redundancy, each expedition will pre-deploy a backup MCAV & ERV. If these backup craft are not needed, they will become the prime equipment for the next expedition.**
Upon nearing Earth, the crew enters the Command Module and undocks from the ERV for Earth entry and landing. The ERV is discarded into Solar Orbit....
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#7
by
astrobrian
on 29 Jul, 2006 14:27
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Why not have the assembled MTV riding near the ISS? Send the CEV to dock with the ISS then ferrying crew back and forth to the MTV. The ISS can then after that keep the CEV around as a lifeboat if needed for them. Not sure if orbital dynamics would allow the MTV to get to Mars from that inclination or not but just a thought.
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#8
by
MATTBLAK
on 29 Jul, 2006 14:50
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You're right; the ISS inclination would make the propellant situation for Trans-Mars Injection punishingly difficult.
Also; except for elaborate concept art and unavoidable, high-mass designs, nobody seems to have a clear idea what a Mars Transfer Vehicle (with BIG aerocapture shield) would look like. With a combined *disposable* CEV and Mission Module for the outbound leg only: you could base the MM on say, a double-SpaceHab module 'chassis' (with attached solar arrays and life-support module), a Mir/Zvezda class vehicle or even an evolved Bigelow inflatable. To coin both a phrase and a trend, this would be using "off-the-shelf" hardware. Although any Mission Module would need a lot more radiation shielding for interplanetary flight than for Earth orbit. More than twice the rated thickness of the CEV's polyethylene shielding, I should think.
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#9
by
mong'
on 29 Jul, 2006 15:05
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MATTBLAK - 29/7/2006 4:01 PM
Also, someone asked earlier; is the CEV going to go to Mars? For a Mars mission architecture, I've looked hard at this question and one of the options, incorporating classical Mars Semi-Direct features, might seem to be thus:
hmm, don't forget the old saying "travel light..."
in your plan, the CEV and MM are not really useful, they've got to weigh at least 40 tons, that is A LOT of deadweight and they aren't really needed. If you want to provide more space to the crew, then increase the size of the HAB, it might be useful to have more living space for a 1.5 years stay on mars.
The ONLY use I can find for the CEV (i.e: where it is really useful and not just deadweight to carry) is as the earth return capsule, and this will probably be sent two years before the crew along with the earth return vehicle.
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#10
by
rumble
on 29 Jul, 2006 15:41
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mong' - 29/7/2006 9:52 AM
The ONLY use I can find for the CEV (i.e: where it is really useful and not just deadweight to carry) is as the earth return capsule, and this will probably be sent two years before the crew along with the earth return vehicle.
spooky...Upon arrival at Mars, and after docking with the Earth Return Capsule for initial check-out, the report comes back, "It's DEAD, Jim!"
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#11
by
mong'
on 29 Jul, 2006 15:55
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yes, in that case I guess you're pretty scr*wed !
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#12
by
zinfab
on 29 Jul, 2006 21:30
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Couldn't the CEV provide some redundacy features for most of the space profiles of a Mars mission? RCS, computers, lifeboat scenarios, etc?
Of course, as currently designed, a CEV is only a 6 month vehicle. It would need modifications to be useful for a whole Mars mission.
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#13
by
astrobrian
on 29 Jul, 2006 22:01
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Or be designed with the ability to be shut down for periods of time ala Apollo 13 style but done intentionally. Then on the way back during TEI it can be fired up again to bring them home
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#14
by
mong'
on 29 Jul, 2006 23:51
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I think there is talk of extending the "rest" period of the CEV to 7 months
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#15
by
MATTBLAK
on 30 Jul, 2006 00:31
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mong' - 30/7/2006 1:52 AM
MATTBLAK - 29/7/2006 4:01 PM
Also, someone asked earlier; is the CEV going to go to Mars? For a Mars mission architecture, I've looked hard at this question and one of the options, incorporating classical Mars Semi-Direct features, might seem to be thus:
hmm, don't forget the old saying "travel light..."
in your plan, the CEV and MM are not really useful, they've got to weigh at least 40 tons, that is A LOT of deadweight and they aren't really needed. If you want to provide more space to the crew, then increase the size of the HAB, it might be useful to have more living space for a 1.5 years stay on mars.
The ONLY use I can find for the CEV (i.e: where it is really useful and not just deadweight to carry) is as the earth return capsule, and this will probably be sent two years before the crew along with the earth return vehicle.
Er... Did you actually read my post? Obviously not. Try and be open to new ideas: Even I have changed my opinion from the SRB-based Ares 1 CLV to an EELV based launcher. That wasn't easy for me
The module purposes and masses were mentioned there. With the proposed architecture, the CEV is the cockpit, the Mission Module is the living quarters for six months (or so) on the outbound voyage; HARDLY "dead weight" (roll eyes). And the attached Habitat/Lander is the direct descent to the Martian surface vehicle, which they live in for the 18 months on Mars (like this Mars Society project on Devon Island --
http://www.marssociety.org/arctic/images/fmars01.jpgPresumably, they may also have an inflatable Habitat to expand their living volume, a scenario now more likely that the Bigelow prototype has worked so well. The heavy CEV & MM combination DON'T go into orbit or land on Mars; that would take a big aeroshell and/or a LOT of propellant. The Cargo/Ascent Vehicle would be very similar to the Nasa Design Reference Mission 3 concept of mounting the CEV capsule on top of the Ascent Stage. THIS would be the Earth Return Capsule and is an idea more than a decade old, not my idea: I've merely looked at 'off-the-shelf' options that don't require ALL the vehicles and modules to last the whole 2.5 year mission with flawless reliability. Also, there are some robust abort options in my architecture, which I should dig up and perhaps re-post. My original posts on this subject are a few months old now.
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#16
by
MATTBLAK
on 30 Jul, 2006 00:50
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#17
by
TyMoore
on 30 Jul, 2006 03:18
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For long duration "Sleep Mode" you'd have to definately put the module in a "keep alive mode:" batteries would have to be charged; heaters would have to keep various components at the proper temperatures to ensure proper operation; pressure and integrity checks. I would imagine that every couple of weeks, a maintenance 'reboot' of the CEV's basic systems would probably need to be performed to check the various electronic control, instramentation, and computer systems from degradation from radiation exposure and thermal cycling fatigue.
Also, I'm not sure what kinds of things would need to be done to ensure the health of an inertial navigation system: I recall that Apollo's INS gyroscopes were sometimes a bit 'twitchy,' and were never intended to be shut down. I suppose that rebooting the CEV's system would also mean fetching the current state vectors from the main mission vehicle so that the CEV would 'know' where it was. A check against certain stars should verify the functionality of the CEV's navigation equipment. I'm not sure how big or small such equipment would be for the CEV--surely it would be smaller than Apollo's. If the equipment is small enough, perhaps certain spares could be carried on board for mission critical components.
As far as the 'keep alive' power; I would imagine that something on the order of a few hundred watts to something less than a kilowatt would be needed. I know that some heaters can use several hundred watts of power, but most would be pretty small. The aggregate 'sleep mode' usage would average around 500W or less, I would imagine (this is a total WAG on my part.)
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#18
by
lmike
on 30 Jul, 2006 03:43
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I can't think of a "one off" Mars expedition. It'd have to be a system. Relying on an infrustructure, well tested systems. Redundancy. Retranslation.
I think whatever the mission profile, given the current attitudes towards loss of life in space it would launch in at least a double redundancy mode. 2*n MTVs/etc... so that the folks can "jump off" (what delta-V?!) onto an Earth escape craft. Perhaps would require a "prepped" Mars landing site. Pre launched supplies, generators, oxygen, etc...
My take is we can't possibly mount a Mars expedition until we can *massively* send humans into space. "Space" as LEO or the Moon. Otherwise it's dice roll. What government organizations would stand for such a dice roll? We'd need a Mars bent strong willed dictator.
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#19
by
mong'
on 30 Jul, 2006 10:45
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MATTBLAK - 30/7/2006 2:18 AM
When the Mission Stack approaches Mars, the crew transfers to the MarsHab-Lander and conducts a direct aero-entry and landing on Mars, next to a pre-landed Mars Cargo-Ascent Vehicle (MCAV). The CEV & MM, their supplies and design life expired, are discarded into solar orbit.
that was the part I was referring to, the injection stage goes to all this trouble to haul a CEV and a MM to mars only to discard them 6 months later. that is a waste of precious mass. if, on the contrary, you discard the MM and add the saved mass to the MarsHab-lander, it will mean more capability and safety on the martian surface (and thus for the biggest part of the mission), astronauts confined for 1 and a half year on an alien world will be dying for one more pound of supplies or scientific instruments.
MATTBLAK
Er... Did you actually read my post? Obviously not. Try and be open to new ideas: Even I have changed my opinion from the SRB-based Ares 1 CLV to an EELV based launcher. That wasn't easy for me
I am sorry if i gave you that impression, I really didn't mean to bash you, I was just pointing out what I think is a flaw in your reasoning.
I enjoy your contributions Matt as I'm sure a lot of folks here do, please keep it up
