CEV derived vehicles

[tomnackid]

Preface:<br />Since the CEV is what NASA is building I don't want this thread to turn into a childish rant about what would be "cooler" or "Why doesn't NASA listen to my ideas--just 'cause I'm an eight grader with a D in math doesn't mean I can't design spaceships better than some dumb professional engineer!" or some such nonsense. <br /><br />So here goes:<br /><br />There was quite a bit of discussion on another board about whether or not the CEV will/should have an airlock for missions that require extensive EVAs. The conclusion was that unless the airlock was an inflatable (a la Voshkod) or a separate mission module (launched by a separate booster? Expensive and complicated.) the CEV will have to decompress for EVAs like Apollo and Gemini did. After looking at the illustrations of the CEV and service module it seems like there could be plenty of room in the SM for an airlock, especially in a CEV optimized for LEO missions where the SM will need far less in the way of tankage. This will mean putting an access hatch in the heat shield. I know a lot of people freak out when this is proposed, but the concept was tested successfully as far back as the Gemini B of the 1960s. Also, the Shuttle has three rather large hatches in it's heat shield for landing gear plus smaller ones for fuel feeds and they have never caused a problem. <br /><br />This got me thinking that this concept could lead to the CEV becoming the basis for a fleet of spacecraft customized for specific missions--space station resupply, space station construction, on orbit servicing, deep space exploration, etc. The Baseline CEV could morph into a comprehensive system that resembles the old "Big Gemini" concept. (See the diagram below.) Andrews Aerospace has already published conceptual designs for a 10 seat variant of the CEV.<br /><br />Any other ideas about how the basic CEV could be adapted as a multi-role spacecraft?<br />

 

[Robert_D]

Good to be thinking about future offshoots.<br />I think for an airlock they would probably use an LSAV ascent stage without an engine and avionics. It could sit behind the SM as in Apollo and a translation made in orbit to dock. The LSAV is expected to have an airlock to allow egress on the moon for 2 crew while the other 2 stay aboard. Don't know if a 5 segment stick could loft both. But if we assume that EVA's are likely only when major new components of ISS or some other structure would fly, The airlock could go up with the cargo and the LSAV/Airlock would bcome the docking point. <br />

 

[josh_simonson]

After launch the CEV could undock from the SM, rotate 180' and re-dock with it - allowing them to use the front airlock only instead of having one on both end (and one through the TPS).<br />

 

[tomnackid]

I thought of that. I don't know which poses the greater risk--A hatch in the heat shield or an on orbit docking maneuver.

 

[mikejz]

How about an exterior inflatable tunnel that would go between the CEV and the SM?

 

[mlorrey]

thru-tps hatches are proven functional (google Gemini B or Gemini 2).

 

[tap_sa]

<font color="yellow">" I don't know which poses the greater risk--A hatch in the heat shield or an on orbit docking maneuver."</font><br /><br />If the maneuver exposes heatshield that wouldn't be nice for a long mission. An additional module behind SM sounds good. Sort of like Soyuz but OM in the back instead of front.

 

[gaetanomarano]

<br />the drawing is the "old big Gemini" or the Andrews' Aerospace design?<br /><br />about airlock/EVA... CEV can't do any shuttle-like assembly/repair...<br /><br />CEV is planned to dock/undock the LSAM and (a few times) the ISS... clearly that missions don't need any EVA and an airlock/orbital-module may be only an extra weight/cost to launch in space<br /><br />I don't think it may be made in next 20 years since NASA want to use the CEV also for Mars (a mission very away from now!)<br /><br />also, a big-CEV (or big-Gemini) need a big-CLV ...extra-time, extra-(high)-costs, extra-problems, extra-procedures... can NASA do all this with planned VSE funds?

 

[mikejz]

You should be able to get a few extra tons of weight if you moved from a 4 segment + SSME to a 5 segment + SSME.

 

[gaetanomarano]

<br />the evolution you quote may give 6 extra-tons... sufficient for an orbital module<br /><br />but the problem is... is it really necessary? ...for which missions? ...and when? ...in next 20 years (while using CEV for moon and ISS) or after?<br /><br />also... LSAM (for moon) and ISS (for orbital) already are some (bigger) extra module... the "CEV-extra-module" appear a duplication without a precise mission

 

[john_316]

I predict the CEV they envision for mars will be twice the size of the current CEV and if it isnt the SM will become a CM+SM+??? Perhaps the CEV will then be the MEV+MSM and MTV<br /><br />Whatever else they need there.<br /><br />My question is this. Are they going to land the CEV on Mars then Lift it off again with a smaller rocket the size of perhaps a 2 Segmented SRB? I know they want to use Methane so why not just build the DC-Y varaint fo that mission as the lander.<br /><br />That has to be considered too...<br /><br />Besides they could always take along a ISS module to add room and comfort on the long trip if its a Chemical one.<br /><br /><img src="/images/icons/smile.gif" /><br />

 

[nacnud]

<font color="yellow">Are they going to land the CEV on Mars then Lift it off again with a smaller rocket the size of perhaps a 2 Segmented SRB? <br /><br /><font color="white">No it apears the CEV stays in orbit.</font></font>

 

[gunsandrockets]

"I predict the CEV they envision for mars will be twice the size of the current CEV and if it isnt the SM will become a CM+SM+??? Perhaps the CEV will then be the MEV+MSM and MTV"<br /><br />The biggest challenge for the block 3 Mars CEV is Earth-direct-return reentry speed of 14 km/s. The standard semi-ballistic capsule Crew Module with a lift to drag of 0.3 could hit 16 gs under that condition.<br /><br />I expect the CM of the block 3 CEV will be modified to improve it's reentry capability. Maybe an oversize inflatable ballute would supplement the standard heatshield. Perhaps a non-symmetric heat shield, or the addition of body flaps could improve the standard capsule lift to drag enough without radically altering the capsule design. It won't surprise me though when the time comes if the block 3 CEV replaces the original semi-ballistic capsule with a simple symmetric bi-conic lifting body capsule with l/d ratio of 0.6. <br />

 

[gunsandrockets]

"I think for an airlock they would probably use an LSAV ascent stage without an engine and avionics. It could sit behind the SM as in Apollo and a translation made in orbit to dock. The LSAV is expected to have an airlock to allow egress on the moon for 2 crew while the other 2 stay aboard. Don't know if a 5 segment stick could loft both. But if we assume that EVA's are likely only when major new components of ISS or some other structure would fly, The airlock could go up with the cargo and the LSAV/Airlock would bcome the docking point."<br /><br />Interesting idea about modifying the LSAM Ascent Module. A modified Ascent Module would be a bit of overkill just to provide an airlock for the CEV though, and the CEV Crew Module is already pretty spacious for LEO jobs. On the bright side a CLV could probably loft both the CEV and the AM if the Service Module of the CEV was fueled only halfway.<br /><br />NASA specifically designed the CEV oversize in order to avoid ever having to use an orbital module though. That still leaves the question of an airlock. I'd go with the inflatable airlock option. It's seems the simplest method that would require the fewest modifications to the CEV.<br /><br />

 

[mattblack]

**Forgive me, but graphics aren't my strong point: If anybody wants to create some for my mission architecture proposal, feel free!<br /><br />I used to mess around with the idea of a CTV to-and-from Mars, but I wondered if such a vehicle might be quite massive and have to protect a large Earth Return propellant payload from the fires of aerobraking into Martian orbit? Not to mention having to be fully reliable and man-rated for the 2.5+plus years of the mission.<br /><br />In an earlier post(s) I laid out an architecture like this:<br /><br /> />>>3x launches: 2x HLV, 1x "Single Stick" SRB. <br /><br />LAUNCH #1): HLV with 1x Mission Module (crew habitat for outbound flight), 1x 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 50 tons of propellant leftover from placing MarsHab-Lander & MM in LEO. <br /><br />LAUNCH #2): HLV with fully-fuelled EDS (about 120 tons prop.) EDS docks with first EDS, MM & MarsHab-Lander. This is the "Mission Stack". <br /><br />LAUNCH #3): CEV with crew of 6 on a "Single-Stick" launcher. CEV docks with Mission Stack and the Stack burns the approx. 170 tons of EDS 1 & 2 propellants (more than twice Apollo quantities) for Trans-Mars Injection . <br /><br />The CEV functions as the Command & Control center for the outbound journey, as has a six-month or more 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 3x Shuttle Mid-Decks, or about 4500 cubic ft in volume. Cramped, sure, but do-able. Electrical power for the Mission Stack <div class="Discussion_UserSignature"> <p> </p><p>One Percent of Federal Funding For Space: America <strong><em><u>CAN</u></em></strong> Afford it!!  LEO is a <strong><em>Prison</em></strong> -- It's time for a <em><strong>JAILBREAK</strong></em>!!</p> </div>

 

[frodo1008]

The problem with all of these current plans for human Mars exploration is that they don't take most of the problems of such a trip into account. And, yes, I have read all of Zubrin's excellent books, and agree totally with him on using the resources of the planet itself to reduce the mission costs! It is truly a great idea!<br /><br />Beyond this however, Zubrin is an incredibly optimistic mission planner!<br /><br />The reason for first going to the moon is that it is quite possible in the reasonably near future, with the current NASA funding! <br /><br />Going on to Mars (unlike some that seem to say that it will actually be easier that going to the moon, such people are living in denial as far as I am concerned) is going to be FAR harder!<br /><br />Here are just some of the KNOWN problems!<br /><br />The main one is simply the enormous difference in the distance to Mars as compared to the distance to the moon!! Any craft that runs into trouble while millions and millions of miles from the Earth is certainly not going to have the option of an Apollo 13 style rescue, now is it!!! I would FAR rather see the mission costs go up to $200 billion or more, than have a $50 billion dollar mission, and have the dubious pleasure of watching some of the worlds finest slowly die!! The reason for such an increase in cost to ensure mission success is quite simple. Redundancy, redundancy, redundancy!!! <br /><br />In no way should we send just one manned craft to Mars! That is a definite plan for disastrous failure!! Enough people should be sent in enough vehicles that if one vehicle is actually totally lost there is still enough room in the remaining vehicles to successfully complete the mission!! <br /><br />Then there are other problems that while less important should still be taken into consideration!<br /><br />First, there is the problem of weightless travel for greatly extended times. Even in his books Zubrin realizes this problem. The only answer is to generate a partial gra

 

[nacnud]

<font color="yellow">First, there is the problem of weightless travel for greatly extended times. <br /><br /><font color="white">IIRC I thought the ESAS report called for fast 180 day transfers between Earth and Mars. Given the experience with the ISS I think it likely that astronauts would be able to cope with 0.38g after this time, the real concern is on return to Earth.</font></font>

 

[frodo1008]

As no person has spent 180 days and then tried to do anything in 0.38 gravities, this still remains a problem. <br /><br />Of course, long before we go to Mars we will hopefuly at least be staying for at least this long in an 0.16 reduced gravity on the moon! So we should have some experience with at least a similer condition, the only way to truly discover what problems might be would be to have an astronaut, or astronayts stay for these 180 days on the ISS and then immediately go on to the moon without landing on the Earth in the meantime, but I think this is highly unlikly or even impossible in the time frame needed!<br /><br />Perhaps a small, spin stabilized space station with facilities for staying at both zero gravity and 0,38 gravity would be possible. Expensive, but possible! We have a LONG way to go before going on to Mars!!<br /><br />I am NOT against going to Mars, but I do think a dose of reality for some of the more enthusiastic Mars explorers on these boards is appropriate at this time!

 

[rsp1202]

This one is still a favorite. Wish I could find larger image.

 

[simcosmos]

Hehe, yep I also could not find a larger image. To compensate that, from some time now that I used one of those cool programs that allow us to artificially increase an image resolution without introducing too much distortion (by using fractal interpolation). For this case, I used Image Analyzer ( http://meesoft.logicnet.dk ) <br /><br />Still not perfect (it can be improved) but a little better than the smaller pic, I guess <img src="/images/icons/wink.gif" /><br /><br />António

 

[rsp1202]

Better. Thanks.

 

[gunsandrockets]

Hmmm...sounds like Mars semi-direct plan from NASA, but with chemical EDS.

 

[gunsandrockets]

Here is a link to some large detailed images of the older NASA CEV concept, which was a biconic-lifting-body capsule.<br /><br />http://images.spaceref.com/news/2005/biconic.cev.l.jpg

 

[JonClarke]

Frodo<br /><br />I know, who am I to argue with the ring bearer, but I will have to take some issues with what you said:<br /><br />"In no way should we send just one manned craft to Mars! That is a definite plan for disastrous failure!! Enough people should be sent in enough vehicles that if one vehicle is actually totally lost there is still enough room in the remaining vehicles to successfully complete the mission!"<br /><br />It depends what you mean by this. I can think of three different ways spacecraft level redundancy could be supplied.<br /><br />1) Complete doubling of crewed spacecraft. Two transit spacecraft, two landers. There are two things wrong with this. <br /><br />First is the cost. Not only are you sending tow of everything, but each spacraft has to be twice as capable. This triples the mission cost. It's all very well to say that you are prepared to accept a quadrupling of cost for increased safety, but realistically there have to be limits.<br /><br />The second is that is tripling the costs actually gets you very little improvement in safety, and in someways the mission is actually more dangerous. <br /><br />Let's divide the mission into phases. There are two launches and two entries, one of each at mars and earth, separated by two cruise phases and the time on the surface. Launch and entry are the most dangerous, let's assign a 1% risk of total crew loss. The cruise and Mars surface phase are much safer, let's assign a 0.1% risk of total crew loss. <br /><br />Without doubling up the probability of completing the entire mission safely is 96% if you double it up you actually double the number of high risk events, landing and launch, the probably of a entire mission being completed safely actually falls to 92%. Because you do get some redundancy you do increase the probability of completing the mission with at least some of the crew to 97%. <br /><br />2) You could send a accompanying spacecraft unmanned. Because they don't have to be twice the <div class="Discussion_UserSignature"> <p><em>Whether we become a multi-planet species with unlimited horizons, or are forever confined to Earth will be decided in the twenty-first century amid the vast plains, rugged canyons and lofty mountains of Mars</em>  Arthur Clarke</p> </div>