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SLS / Orion / Beyond-LEO HSF - Constellation => Orion and Exploration Vehicles => Topic started by: Zoomer30 on 07/27/2006 04:52 am

Title: The "Mars" part of the CEV mission confuses me....
Post by: Zoomer30 on 07/27/2006 04:52 am

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).

Title: RE: The "Mars" part of the CEV mission confuses me....
Post by: punkboi on 07/27/2006 06:36 am

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...

Title: Re: The \
Post by: mong' on 07/27/2006 11:36 am

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

Title: RE: The "Mars" part of the CEV mission confuses me....
Post by: Jim on 07/27/2006 12:00 pm

Quote

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

Title: Re: The "Mars" part of the CEV mission confuses me....
Post by: PurduesUSAFguy on 07/29/2006 01:30 pm

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)

Title: Re: The "Mars" part of the CEV mission confuses me....
Post by: hyper_snyper on 07/29/2006 01:48 pm

Quote

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.

Title: RE: The "Mars" part of the CEV mission confuses me....
Post by: MATTBLAK on 07/29/2006 02:14 pm

Quote

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....

Title: Re: The "Mars" part of the CEV mission confuses me....
Post by: astrobrian on 07/29/2006 02:27 pm

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.

Title: Re: The "Mars" part of the CEV mission confuses me....
Post by: MATTBLAK on 07/29/2006 02:50 pm

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.

Title: RE: The "Mars" part of the CEV mission confuses me....
Post by: mong' on 07/29/2006 03:05 pm

Quote

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.

Title: RE: The "Mars" part of the CEV mission confuses me....
Post by: rumble on 07/29/2006 03:41 pm

Quote

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!"

Title: The "Mars" part of the CEV mission confuses me....
Post by: mong' on 07/29/2006 03:55 pm

yes, in that case I guess you're pretty scr*wed ! :)

Title: Re: The "Mars" part of the CEV mission confuses me....
Post by: zinfab on 07/29/2006 09:30 pm

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.

Title: Re: The "Mars" part of the CEV mission confuses me....
Post by: astrobrian on 07/29/2006 10:01 pm

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

Title: Re: The "Mars" part of the CEV mission confuses me....
Post by: mong' on 07/29/2006 11:51 pm

I think there is talk of extending the "rest" period of the CEV to 7 months

Title: RE: The "Mars" part of the CEV mission confuses me....
Post by: MATTBLAK on 07/30/2006 12:31 am

Quote

mong' - 30/7/2006  1:52 AM

Quote

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.jpg

Presumably, 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.

Title: RE: The "Mars" part of the CEV mission confuses me....
Post by: MATTBLAK on 07/30/2006 12:50 am

In fact, here's the thread that had my architecture and it's abort options discussed in greater detail:

http://forum.nasaspaceflight.com/forums/thread-view.asp?tid=3078&posts=20&mid=44286&highlight=mission+module+mars+flyby&highlightmode=1&action=search#M44286

Title: RE: The "Mars" part of the CEV mission confuses me....
Post by: TyMoore on 07/30/2006 03:18 am

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.)

Title: RE: The "Mars" part of the CEV mission confuses me....
Post by: lmike on 07/30/2006 03:43 am

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.

Title: RE: The \
Post by: mong' on 07/30/2006 10:45 am

Quote

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.

Quote

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

Title: RE: The "Mars" part of the CEV mission confuses me....
Post by: mong' on 07/30/2006 10:58 am

Quote

lmike - 30/7/2006  5:30 AM

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.

I disagree. every spaceflight has a great deal of risk, people have died doint it and people WILL die doing it, that's a given. the most detaield mars mission sudies (i.e:NASA DRM's) may sound a little tricky with a small hab, 2.5 years missions and ISRU, but you can build in a great deal of safety options. the most challenging system will probably be a life support system capable of running for years without a glitch, it's a challenge but merely an engineering challenge, I'm confident it will be overcome by the engineers of 2020.
as for public opinion, I, for one believe the prospect of a mission to mars will generate more wonder than criticism, call me naive but I feel any danger of such a mission will only strengthen the public's respect for astronauts and the space program in general

Title: RE: The "Mars" part of the CEV mission confuses me....
Post by: MATTBLAK on 07/30/2006 11:31 am

Thank you, Mong for your compliments.

Actually the original and 'traditional' Mars Direct architecture is still my favourite. Perhaps a larger, combined Mission Module/Lander would probably be ideal: maybe the MM could be reduced to a simple food & water pantry/storm shelter, with the crew living in the Habitat Lander both outbound and on the Martian surface. Using the MM consumables would save the Hab/Landers supplies for Mars and less mass would be jettisoned before arrival at Mars.

And your statements about risks and challenges of spaceflight are bang on. ;)

Title: Re: The "Mars" part of the CEV mission confuses me....
Post by: mong' on 07/30/2006 11:56 am

I agree about Mars Direct, it is also my favorite for its simplicity, but I am afraid such a mission will be very tight wrt to supplies and living space, if it worked with the numbers given (and that is a "if") there would not be much room left for scientific instruments and redundant systems. I think something along the lines of the DRM III, even if it means more launches (and thus more complexity) would have a higher scientific payoff, 6 people with the adequate scienntific payload could get the most out of the 1.5 year stay.

Title: Re: The "Mars" part of the CEV mission confuses me....
Post by: MATTBLAK on 07/31/2006 06:57 am

Agreed. I've always thought the DRM-3 gives extra safety by having extra vehicles that also provide more living volume. Also, I think a crew of 5 would be the best number for a Mars mission. Why? Extra redundancy over 4 persons and about 16% percent less comsumables needed than for 6 persons.

Title: Re: The "Mars" part of the CEV mission confuses me....
Post by: mong' on 08/03/2006 09:56 pm

recent comment by Griffin:
"Next year, I hope to make plans as to how to carry out manned missions to Mars, building on the heavy-lift launch vehicles, landers, and other capabilities from the lunar exploration architecture."

Full transcript here: http://www.spaceref.com/news/viewsr.html?pid=21597

Title: RE: The "Mars" part of the CEV mission confuses me....
Post by: lmike on 08/04/2006 05:04 am

Quote

mong' - 30/7/2006  3:45 AM

Quote

lmike - 30/7/2006  5:30 AM

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.

I disagree. every spaceflight has a great deal of risk, people have died doint it and people WILL die doing it, that's a given. the most detaield mars mission sudies (i.e:NASA DRM's) may sound a little tricky with a small hab, 2.5 years missions and ISRU, but you can build in a great deal of safety options. the most challenging system will probably be a life support system capable of running for years without a glitch, it's a challenge but merely an engineering challenge, I'm confident it will be overcome by the engineers of 2020.
as for public opinion, I, for one believe the prospect of a mission to mars will generate more wonder than criticism, call me naive but I feel any danger of such a mission will only strengthen the public's respect for astronauts and the space program in general

It's great wishful thinking (in the good sense), and I wish you were right, but as it currently stands every human lost even in LEO resounds as "NASA's kaput" on the ground.  And results in a 3 year delay in manned space operations.  So a single Mars expedition with no chance for the crew to survive (as ephemeral as it would be) would be a big no-no in the current environment.

Title: Re: The "Mars" part of the CEV mission confuses me....
Post by: publiusr on 08/18/2006 07:45 pm

Quote

mong' - 3/8/2006  4:43 PM

recent comment by Griffin:
"Next year, I hope to make plans as to how to carry out manned missions to Mars, building on the heavy-lift launch vehicles, landers, and other capabilities from the lunar exploration architecture."

Full transcript here: http://www.spaceref.com/news/viewsr.html?pid=21597

I look forward to more. Mike Griffin is the best NASA Chief we've had in a generation.

Title: Re: The "Mars" part of the CEV mission confuses me....
Post by: Jim on 08/18/2006 07:48 pm

That is debatable.  Just because he advocates a big booster doesn't qualify him as the 'Best".  He may end up damaging the agency more by cutting the R&D

Title: Re: The "Mars" part of the CEV mission confuses me....
Post by: publiusr on 08/18/2006 08:39 pm

J-2 is R&D too. He is helping replace the damage done to propulsion under that fool Goldin.

Title: RE: The "Mars" part of the CEV mission confuses me....
Post by: Zoomer30 on 08/18/2006 10:31 pm

Persoanlly I would like the "faster" idea myself.  the shorter the trip to Mars the less time you spend outside the Earth mag field and the less chance you have of getting nailed by a CME.  Does not matter what kind of solar storm protection you have then, a good sized CME can ruin your whole weekend.  

Its like that show they had on Discovery a few months back.  It was a BBC program about a "grand tour" of the solar system.  One of the crew developed cancer and died during the trip, presumbly due to cosmic rays.  Once issue discussed was the TREATMENT he had to undergo to try and save him.  The chemo drugs contaminated the water so the crew had to take medications to counter-act that.  Pretty good show, cant remember the name of it.

Title: Re: The "Mars" part of the CEV mission confuses me....
Post by: Spacely on 08/19/2006 12:42 am

Quote

publiusr - 18/8/2006  1:26 PM

J-2 is R&D too. He is helping replace the damage done to propulsion under that fool Goldin.

Isn't the RS-68 for CaLV use going to be an upgraded/uprated version of the current model? Yeah, it's not as flashy as some cleansheet heavy lift engine, but it's still going to be innovative and advanced as far as chemical engines go.

Title: Re: The "Mars" part of the CEV mission confuses me....
Post by: publiusr on 08/22/2006 10:43 pm

I would like to See Ares V with a wide-body core--but I'll take DSD to nothing.

Title: Re: The "Mars" part of the CEV mission confuses me....
Post by: tom nackid on 08/24/2006 09:38 pm

Quote

PurduesUSAFguy - 29/7/2006  8:17 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)

Have you calculated the mass of the fuel needed for a returning Mars ship to rendezvous with a ferry in LEO? I haven't, but I would bet that it is a lot more than the mass of a CEV capable of reentering Earth's atmosphere from a Mars return trajectory. Rendezvousing with ferries or space stations in LEO sounds great but in space it takes as much fuel to slow down as it did to accelerate in the first place.

Title: Re: The "Mars" part of the CEV mission confuses me....
Post by: Avron on 08/25/2006 05:02 am

Quote

tom nackid - 24/8/2006  5:25 PM

Quote

PurduesUSAFguy - 29/7/2006  8:17 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)

Have you calculated the mass of the fuel needed for a returning Mars ship to rendezvous with a ferry in LEO? I haven't, but I would bet that it is a lot more than the mass of a CEV capable of reentering Earth's atmosphere from a Mars return trajectory. Rendezvousing with ferries or space stations in LEO sounds great but in space it takes as much fuel to slow down as it did to accelerate in the first place.

Not quite true... there is always aerobraking and trust levels in or out of the soup (i.e. vacuum rating vs sea level)... and good old gravity.. but yes, a lot fuel is required for chemical engines.. these is always the Nuclear   option...

Title: Re: The "Mars" part of the CEV mission confuses me....
Post by: punkboi on 08/25/2006 05:20 am

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Avron - 24/8/2006 9:49 PM

Quote

tom nackid - 24/8/2006 5:25 PM

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PurduesUSAFguy - 29/7/2006 8:17 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)

Have you calculated the mass of the fuel needed for a returning Mars ship to rendezvous with a ferry in LEO? I haven't, but I would bet that it is a lot more than the mass of a CEV capable of reentering Earth's atmosphere from a Mars return trajectory. Rendezvousing with ferries or space stations in LEO sounds great but in space it takes as much fuel to slow down as it did to accelerate in the first place.

Not quite true... there is always aerobraking and trust levels in or out of the soup (i.e. vacuum rating vs sea level)... and good old gravity.. but yes, a lot fuel is required for chemical engines.. these is always the Nuclear option...

And then the Global Network Against Weapons & Nuclear Power will come in to rain on the parade... :)

Title: Re: The "Mars" part of the CEV mission confuses me....
Post by: kevin-rf on 08/25/2006 01:09 pm

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tom nackid - 24/8/2006  4:25 PM

Have you calculated the mass of the fuel needed for a returning Mars ship to rendezvous with a ferry in LEO? I haven't, but I would bet that it is a lot more than the mass of a CEV capable of reentering Earth's atmosphere from a Mars return trajectory. Rendezvousing with ferries or space stations in LEO sounds great but in space it takes as much fuel to slow down as it did to accelerate in the first place.

Actually, it would take less fuel to deccelerate since you have to also accelerate your decceleration fuel. Anyway, it is still a fair amount of fuel that you don't need if you go straight for reentry or aero breaking.

Title: Re: The "Mars" part of the CEV mission confuses me....
Post by: tom nackid on 08/25/2006 01:30 pm

And for aerobraking you still need to bring along a heat shield anyway, why not just make it reentry capsule and save fuel and avoid the dangers of a rendezvous in LEO?

Title: Re: The "Mars" part of the CEV mission confuses me....
Post by: Avron on 08/25/2006 04:21 pm

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tom nackid - 25/8/2006  9:17 AM

And for aerobraking you still need to bring along a heat shield anyway, why not just make it reentry capsule and save fuel and avoid the dangers of a rendezvous in LEO?

EH.... reentry capsule without a heat shield is deadly....

Title: Re: The "Mars" part of the CEV mission confuses me....
Post by: imfan on 08/25/2006 05:53 pm

:-) he was talking about heatshield for the whole battlestar galactica needed for mars trip. not to mention structural limits that would probably prevent such a violent treating to big structure like that. heatshield for capsule is nothing compared to previous

Title: Re: The "Mars" part of the CEV mission confuses me....
Post by: tom nackid on 08/25/2006 06:46 pm

Yes. A sturdy little capsule capable of reentering the Earth's atmosphere from a Mars return trajectory would seem (to me anyway) as being a lot lighter, cheaper, and safer than trying to slow down the whole "Battlestar Galactica" to rendezvous with a ferry or station in LEO.

Of course things like nuclear propulsion and reusable "cycler" spacecraft change everything. But I don't see these happening until AFTER we start our exploration of Mars. Lewis and Clark didn't wait for highways and railroads after all.

Title: RE: The "Mars" part of the CEV mission confuses me....
Post by: oriolesfan61 on 09/05/2006 01:55 am

This wasn't a "stupid" question---I had wondered the same myself! Five astronauts in the CEV CM for 180 days to Mars?! One more person packed in there than for a three-day trip to the Moon?!

Then I read about the "Mars Transfer Vehicle", but searching for that gave me hits for previous human-spaceflight-to-Mars concepts and designs. And some mention of another "_____ [?] Transfer Vehicle" which was still difficult to pin down. I will look further using this more complete information.

Thank you all! :)

Title: Re: The "Mars" part of the CEV mission confuses me....
Post by: Jim on 09/05/2006 02:10 am

The CEV is not the living quarters for the Mars mission, the MTV is.  The CEV goes along as a safe haven, and command center and earth entry vehicle

Title: RE: The "Mars" part of the CEV mission confuses me....
Post by: RedSky on 09/05/2006 04:15 am

This was posted a while ago on another thread... for a European Mars plan... but it shows how going to Mars is soooo much more than a CEV and lander. It's a lot more like one (or more) ISS modules, with probably many levels of propulsion stages and tanks (each of which can be jettisoned when their task is completed), the CEV for earth entry, and of course, some form of lander(s). If you look on page 11 of this document... you'll see how the earth entry vehicle (i.e., CEV type capsule) is dwarfed by everything else.

ftp://ftp.estec.esa.nl/pub/aurora/Human_Missions_to_Mars/HMM_Executive_Summary_Final_Version.pdf


And for those who may not have seen this article at astronautix...  here's a summary of many different Mars plans through the ages:

http://www.astronautix.com/craftfam/martions.htm

Title: Re: The "Mars" part of the CEV mission confuses me....
Post by: kraisee on 09/05/2006 06:57 am

Pub,
DSD does not preclude the 150mT capacity of the Ares-V later.   "Direct" costs less to develop than Ares-I does, so *if* the next three Presidents agree to provide the money for the bigger vehicle, it costs nothing extra compared to Ares.

But if they don't you don't lose the moon and Mars.    The first vehicle is the critical one, not the second vehicle.   If the second vehicle were to be cancelled, NASA isn't blocked from still going to the moon and Mars, they can still go with "Direct", but they couldn't with just Ares-I.   CaLV is removed from the critical path.

Also evolving Direct into the ESAS CaLV is pretty easy compared to evolving the Stick into the 150mT-to-LEO ESAS CaLV design.

With the higher Isp of the SSME, the core does not have to be widened, and that massively reduces the costs of alterations to all the Pads, MLP's, VAB highbays, transport barges and tooling at MAF.   All of that can largely remain as it is and work perfectly.

And there's no reason why you can't put a wider shroud on top of "Direct" either - this 10m diameter paylod shroud looks pretty good on top of DSD IMHO...

Ross.

Title: Re: The "Mars" part of the CEV mission confuses me....
Post by: MATTBLAK on 09/05/2006 08:36 am

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Jim - 5/9/2006  12:57 PM

The CEV is not the living quarters for the Mars mission, the MTV is.  The CEV goes along as a safe haven, and command center and earth entry vehicle

Right on!! If you look at page one of this thread, I recommended for my architecture a Mission Module used for the outbound leg. It could be a Double-SpaceHab, an inflatable or an armoured & upgraded 'double MPLM' ISS module. The habitable volume of such a Mission Module would be in excess of 2500 cubic feet, factoring in the stacks of consumables in the MM, which would enhance the radiation shielding abilities of the module anyway. You could count on there being polyethelene layers more than twice that needed for ISS or the walls of the CEV cabin. Or maybe the 'Block III' Orion would have thicker polyethelene anyway; more than 5-gram per cubic cm.

Title: Re: The "Mars" part of the CEV mission confuses me....
Post by: Jim on 09/05/2006 10:33 am

Just a note, the Spacehab doublemodule can't survive outside the shuttle and it is not very adaptable to other missions.  The flat top reduces the volume and attachment areas

Title: Re: The "Mars" part of the CEV mission confuses me....
Post by: MATTBLAK on 09/05/2006 10:50 am

I meant the outer moldline 'chassis' of the Double-SpaceHab. If you check out the SpaceHab Final presentation, you'll see many concepts for adapting the SpaceHab modules:

http://exploration.nasa.gov/documents/cer_reports.html

Title: Re: The "Mars" part of the CEV mission confuses me....
Post by: Jim on 09/05/2006 11:11 am

Those are all new builds and have nothing in common with the "classic" spacehab modules.

Title: Re: The "Mars" part of the CEV mission confuses me....
Post by: MATTBLAK on 09/05/2006 12:21 pm

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Jim - 5/9/2006  9:58 PM

Those are all new builds and have nothing in common with the "classic" spacehab modules.

Yesss... I KNOW that??!! I meant SpaceHab as a conceptual shorthand. I never meant to refurbish and use the old ones and --

Aww; you know what I meant  :o

Title: Re: The "Mars" part of the CEV mission confuses me....
Post by: Jim on 09/05/2006 01:51 pm

Sorry

Title: Re: The "Mars" part of the CEV mission confuses me....
Post by: MATTBLAK on 09/06/2006 08:55 am

No worries!