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Author Topic: ERV CEV  (Read 12095 times)
Zachstar
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« on: November 21, 2005, 05:56:17 PM »

We can discuss here Ideas on the CEV that's going to get you home.

To begin

I beleve that the T-space CXV redesigned in the ideal solution to this problem. As it is light and can carry 6 people back. Im sure an additional layer of tiles can help get it through the reentry.

http://www.transformspace.com/index.cfm?fuseaction=projects.view&workid=CCD3097A-96B6-175C-97F15F270F2B83AA

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Iceversaka
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« Reply #1 on: November 22, 2005, 09:55:04 AM »

Excellent!

We're cookin now!!!

I can get in here and post, view, and debate.

Can't get into e-mail here at work, but the server doesn't block the forums.
 Very Happy

I think we've pretty much settled on the basic design.

Cyrus had mentioned considering the biconic, but we had to reconsider that after looking at the mass numbers, if I remember correctly.

It might be possible to go back and look at it again.

But there isn't much time to consider it properly, so we should get that debate/discussion over with ASAP, in order that it won't conflict with the rest of the ERV modeling.

Seth
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smoothvirus
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« Reply #2 on: November 22, 2005, 11:44:00 AM »

I think the T-Space CXV could be used as a baseline for the ERV Command Module, but there are a few factors to consider:

1. What's the mass of the CXV vs. the CEV? Which command module would weigh more? Note that there are some things on the CXV which the ERV command module won't need. It wont need the solar panels or the maneuvering engines.

2. We know the biconic design works for re-entry from LEO. But how well would the thermal protection work for a direct re-entry from Mars? I suspect the shielding would need to be beefed up, which would increase the mass. The G-loads are going to be higher too.

That said I think the CEV works as a baseline for the ERV Command Module too - it's just a matter of which solution weighs the least.
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Iceversaka
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« Reply #3 on: November 22, 2005, 04:10:09 PM »

I couldn't find any mass numbers for the CXV from the TSpace website:
http://www.transformspace.com/index.cfm?fuseaction=projects.library&workid=CCD3097A-96B6-175C-97F15F270F2B83AA

This was the most technical document I could find:
http://www.transformspace.com/document_library/media/tSpace_Summary.pdf

Looks like they are using two layers of "Silicone
Impregnated Refractory Ceramic Ablator". SIRCA

Not a bad way to go!

I found a rough figure for the CEV mass at 17,507 kg dry mass. I'm thinking that's including the Service Module. The CEV itself from Aeroshield to docking port I would estimate at about 7,000 kg...ball park figure, plus or minus a few thousand kg since I really am guessing here.

It is mostly empty space inside, while the SM is full of hardware and tanks.
 Happy

And it looks like I was close, the Mars Society lists the CEV upper limit at "CEV capsule would have to be limited to 7.4 tonnes."
http://www.marssociety.org/news/2005/0704.asp

If I needed to make a ball park guess for the CXV, I would guess around 9,000 kg. It's built for 6 people plus cargo. We are only sending 4 people to Mars, and hopefully 4 of them will come back. So 4 people plus a few tons of samples. The CEV is built for 4 people plus cargo.

That link above Dr. Zubrin himself makes a good case for a small CEV, so I guess I don't need to carry on trying to sell it myself. LOL

Putting the Delta Sprint atop the ERV might also work, but it looks like the Sprint is rated for a 3 person crew. Maybe it could be modified for 4 people, but then we have the concern about attaching it to the rest of the ERV via the Radiation access tunnel. Looks like the Sprint has a rocket engine right were the access tunnel would need to go. It probably also doesn't need the service module since the ERV has a good enough service module for the entire return voyage, and after it's dumped just prior to Earth entry interface will require only minimal onboard life support consumables.

Maybe Aftercolumbia can give us a report on how it would stand up to a direct Earth entry from a trans-mars insertion?

Definately looks like the CEV is the way to, unless something new comes up.

Some nice debates and referance material:
http://orbit.m6.net/v2/read.asp?id=17192&recordnum=0
http://aftercolumbia.tripod.com/deltasprint/

Just trying to heat this up, and get some conclusive results. I hate indecision esspeically in the face of a final design! So maybe I should post another poll on here?

EDIT: Remember, if we go with the CEV concept, we'll get a CEV Mark1 & Mark2, both of which will work quite nicely with the ERV.

EDIT: To me the best part about the CEV concept is it works well for ISS, Moon, Mars, and beyond!  Very Happy  With the appropriate support hardware for each mission of course. Much like the Ares upper stage from earlier which can throw mass all the way to Jupiter if need be.

Cheers
Seth
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Zachstar
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« Reply #4 on: November 22, 2005, 05:19:15 PM »

The only arguement left against use of the CEV and use of the CXV is the fact that CXV is designed where the docking port is behind you. Meaning no need to worry about cutting a hole and risking the heat sheild.
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Iceversaka
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« Reply #5 on: November 22, 2005, 06:42:47 PM »

I personally agree with you Zach!

But Cyrus and some of the other project members believe it is a non issue, as there are holes in the heat shield for the shuttle landing gear.

*granted* not leading into a crewed space.

That's why I suggested a Mark2 CEV which would also not have a hole in the heat shield, and it also would support abort options, which (by the looks of it) are limited on the CXV, but not the Delta Sprint. Trade-offs no matter which way you turn!  :lol:

*again*, the Mark1 CEV will satisfy the requirements of not needing abort options for the first set of missions when it would indeed be useless, as has already been discussed. And the Mark2 CEV can satisfy the mission growth flexability for tertiary missions.

Seth
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Zachstar
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« Reply #6 on: November 22, 2005, 07:03:59 PM »

And the shuttle isnt comin back at entry from mars speed.

CXV is light it has to be for it to be able to be lifted by the quickreach 2.

These tiles can be upgraded the solar panels replaced with batteries and reduction to 4 crew with mars cargo.

If there is still an issue you can remove a few of the life support tanks and remove the main engines. That will take a good chunk off the weight.

Seth get an avatar Tongue

BTW about this abort thing...

If the ERV is forced to abort due to a failure you know how many miles you can end up away from the hab? Theres no time to land a new ERV and make new propellant before the crew dies. Even if it lands and they can somehow get out of the CXV. They whould run out of food by the time it could reach earth after making new fuel.

And wait by that time the new ERV has landed and is making fuel for the next crew.

ERV fails at lift off your are dead
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Zachstar
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« Reply #7 on: November 23, 2005, 01:37:51 AM »


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robertsconley65
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« Reply #8 on: November 23, 2005, 11:55:50 PM »

The CRX isn't going to work for mars re-entries. You need the ability to lift the capsule in order to control re-entry loading and have some control over the landing zone. The shapes used by the corona and discoverer capsule don't give that ability. They come in on ballistic trajectories.
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smoothvirus
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« Reply #9 on: November 24, 2005, 11:28:27 PM »

Quote from: robertsconley
The CRX isn't going to work for mars re-entries. You need the ability to lift the capsule in order to control re-entry loading and have some control over the landing zone. The shapes used by the corona and discoverer capsule don't give that ability. They come in on ballistic trajectories.


Yeah, I think that kind of settles it there.

As for the hole in the heatshield being a problem - I think it's an imaginary dragon, to quote Dr. Zubrin.

I have asked numerous people who know way more about spacecraft than me - including real engineers about it, and the unanimous opinion was that it can be made to work. Heatshield hatches have been tested before on the Gemini MOR program.
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Iceversaka
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« Reply #10 on: December 06, 2005, 06:36:31 PM »

Well I don't have the Terry reply regarding CRV vs Sprint.

And I think that settles it....We go with Sprint.

Which frankly I'm quite happy to support.

The ERV already has plenty of habitation support and supplies that it will most definately last the entire return trip, so we don't really need much additional support from the CM, just enough to last after seperation and through re-entry. Hopefully we don't need to orbit loiter.

I assume the Sprint can be beefed up enough to support the full Trans Earth Mars aerobraking speed direct to landing? Is that going to be feasable? or will we need to have some orbit loiter time before landing? Earth Return Landing, that is.

Seth
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aftercolumbia
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« Reply #11 on: December 18, 2005, 04:51:13 PM »

Arrgghh!  I lost my entire post!  (One of the reasons I want to stay with Yahoo Groups)...now my entire hour-long rant is gone and I got just a couple minutes left online.

First off, it's pretty obvious that CXV and Sprint are closer than Sprint and CEV.  I judge CXV as a rather minimalist crew transfer vehicle, even compared to Sprint, and lacks the lifeboat functionality of Sprint.

For mass, the parachute recovery drop test article for the CXV was quoted as full scale and 8100lb (about 3700kg...in my head.)  I think that for a four person vehicle, this is unrealistically low, and I'm expecting full development would come out to about 5500kg at a minimum.  Sprint being in the 8000kg ballpark, will hopefully turn out to be unrealistically pessimistic, thus giving us lots of room to play around with options.  (Note: I'm expecting 5000kg in the Descent Module, with no 3000kg Service Module on the ERV, so don't get too scared.)

I can spot some more holes in CXV, I'm expecting a few changes as study and development progresses (assuming they are pragmatic, of course.)  CXV also has points that shine light on holes in its big sister, the Sprint.  I think the ideal might be to combine the best points of both spacecraft.

More later, I don't want to lose this post too.
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Zachstar
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« Reply #12 on: December 19, 2005, 02:41:48 AM »

I whould suggest getting a notepad that autosaves

http://www.freewarefiles.com/program_8_87_14254.html

This might be usefull
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aftercolumbia
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« Reply #13 on: December 22, 2005, 10:55:28 PM »

Quote from: smoothvirus
I think the T-Space CXV could be used as a baseline for the ERV Command Module, but there are a few factors to consider:

1. What's the mass of the CXV vs. the CEV? Which command module would weigh more? Note that there are some things on the CXV which the ERV command module won't need. It wont need the solar panels or the maneuvering engines.


The CEV is about twice as large as the Sprint, and the Sprint is about twice as large as the CXV.  The CEV is simply too big for our purposes...however, the CXV, as is, may be too small: we will want to bring back samples.

If we go with the CXV as the ERV descent module straight volume, we can trade out the docking port and solar panels for sample containers.  With CXV, we also have no problem launching with the crew in the module if its inverted or normal orientation.  The problem is, well, we only got the one docking port, but that's a problem with Sprint as well.

Either way the best way to launch the DM is with the docking port down (i.e. CXV normal and Sprint inverted.), so that we have the cruise module underneath the descent module.

CEV is big enough that:
a) we don't need a cruise module
b) we can't fit one in anyway

CEV might also be too heavy, at somewhere between 15,000 and 35,000kg.  Sprint is 5000kg, CXV is 3700kg (descent modules only.)

Quote from: smoothvirus

2. We know the biconic design works for re-entry from LEO. But how well would the thermal protection work for a direct re-entry from Mars? I suspect the shielding would need to be beefed up, which would increase the mass. The G-loads are going to be higher too.


Which one?  Base first or nose first?  I expect that any shape that works for LEO will work for high energy entries, if it produces enough lift to relieve decelleration forces while keeping us from skimming out.  8g can be expected to be the absolute maximum permissible non-emergency decelleration force.  Pulling us down further will be about 2 and a half years of living at 0.38g or less, leading to muscular atrophy and osteoatrophy.  I'd say 5g should be put on the page as our "maximum non-emergency entry decelleration load."  I don't know yet how much lift is needed to do this from a Mars-Earth entry.  The shape is most important...and if it gets too hot, we make it bigger at the same mass to reduce drag loading (and therefore entry temperature.)

Quote from: smoothvirus

That said I think the CEV works as a baseline for the ERV Command Module too - it's just a matter of which solution weighs the least.


I, frankly...and I'm sure you know this, don't think we can fly with the CEV (as even if it is realistic, it is no longer Mars Direct if we do.)  The CXV is the lightest solution, but I believe it to be a bit too optimistic for their mass numbers to be reliable (the thermal protection system is what tells me this.)
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aftercolumbia
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« Reply #14 on: December 22, 2005, 11:03:09 PM »

I'm going to go bug them...I know I haven't done much on my http://aftercolumbia.tripod.com website since May 2004, but Delta Sprint's report is still there, and most of it is still current.
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