Lockheed Martin's CEV has two rocket engines

[space_dreamer]

Lockheed Martin Crew Exploration Vehicle seems to have two engines! <br /><br />Why two rocket engines? NASA CEV design had one, as did apollo.

 

[DuhFly]

can you please post the link to the picture.

 

[propforce]

Well, that's directly contradict with NASA's movie on CEV, which only show one engine. <br /><br />You think the Lockheed boys are trying to tell NASA something? <img src="/images/icons/tongue.gif" /> <div class="Discussion_UserSignature"> </div>

 

[mikejz]

Thought:<br /><br />What if the proposal uses the upper stage of the CEV launcher, HLV, or the desent stage of the LM for LOI? <br /><br />

 

[propforce]

<font color="yellow">It still looks small to this untrained eye though. </font><br /><br />Maybe they save space with the astronauts in a "spooning" position instead.... <div class="Discussion_UserSignature"> </div>

 

[tohaki]

<blockquote><font class="small">In reply to:</font><hr /><p>Wait to you guys see the NG/Boeing design !!<p><hr /></p></p></blockquote>When will that be?

 

[propforce]

<font color="yellow">Yes, I would say at least 60% too small. </font><br /><br />... and that's assuming what type of propellant? <div class="Discussion_UserSignature"> </div>

 

[propforce]

<font color="yellow">When will that be? </font><br /><br />Hopefully after the proposal is submitted, at the end of March.... <div class="Discussion_UserSignature"> </div>

 

[mikejz]

There is something about that SM that looks like it was derived from a upper stage design, can't put my finger on it.<br /><br />On a side note: highly, highly, highly unlikely...but maybe the design uses drop tanks....

 

[moonmadness]

seems most people believed the video releases were exactly what the CEV et al was going to look like. And lambasted by some as such.<br /><br />I believe it was just a cut and paste of shuttle parts and Apollo-Gemini (for show only).<br /><br />I for one held out that after concepts and proposals were finalized the end product could very well end up 'looking more advanced" as well as being technologically more advanced than Apollo-Gemini. <div class="Discussion_UserSignature"> <p>I'm not a rocket scientist, but I do play one on the TV in my mind.</p> </div>

 

[spacester]

Nice call. AFAIK all of the material released to date has been repeatedly referred to as 'notional' only.<br /><br />It's one of the burdens of doing the design process correctly: you don't have reliable artwork for the guys upstairs until late in the game. <img src="/images/icons/wink.gif" /> <div class="Discussion_UserSignature"> </div>

 

[gunsandrockets]

"I do not understand the small szie of the service module. There does not seem to be enough room for the job it has to do. The main jon being the approximately 5,500 ft per sec delta V. There is not enough space for the Propellant. "<br /><br />Maybe the SM is smaller because it uses ethanol instead of methane. In addition the SM may seem deceptively small because the conical extension on the rear of the SM does not stand out very much in the illustration.

 

[rybanis]

Still, that thing needs 5.5k ft/sec delta v...<br /><br />The thing is still too small, even if you were using LOX/Hydrogen. <div class="Discussion_UserSignature"> </div>

 

[nacnud]

Well LOX LH2 would take up more room than LOX Hydrocarbon. LH2 isn't very dense, however LH2 would mass less than the equivelent amount of hydrocarbon.

 

[gunsandrockets]

"Still, that thing needs 5.5k ft/sec delta v... The thing is still too small, even if you were using LOX/Hydrogen."<br /><br />You don't seem to understand my point. Let me try to spell it out for you.<br /><br />Liquid methane has a density of 0.433 kg per liter. Ethanol is much denser at 0.789 kg per liter. Therefore ethanol only occupies 55% of the volume that an equal mass of liquid methane occupies. Ethanol only takes up half the space of methane.<br /><br />Thererfore a CEV Service-Module using ethanol instead of methane is considerably smaller even though the total mass is the same.<br /><br />Now ethanol/LOX burning rocket engines have slightly less ISP than methane/LOX rocket engines, so a CEV that uses ethanol would have to be slightly more massive to achieve the same delta V as a CEV that uses methane. Despite this an ethanol Service-Module is still much smaller than one that uses methane.<br /><br />Now if the CEV uses liquid hydrogen instead of methane, the Service-Module would be much much larger since liquid hydrogen is very much less dense than methane. And this is true in spite of the fact than hydrogen is a much better fuel, as far as ISP, than methane.<br /><br />That the new Lockheed-Martin CEV might use ethanol/LOX rocket engines should come as no surprise considering the original lifting-body proposal that Lockheed revealed in May 2005 also used ethanol/LOX. <br /><br />

 

[mikejz]

ethanol?<br /><br />Geez, ADM is pushing for gov't subsidies where ever it can! <img src="/images/icons/smile.gif" />

 

[ragnorak]

<br />Interestingly LM chose LOX/ethanol for its LSAM propulsion for its Concept Exploration & Refinement report.

 

[spacefire]

<font color="yellow">Wait to you guys see the NG/Boeing design </font><br /><br />I'm sure it will be groundbreaking! <div class="Discussion_UserSignature"> <p>http://asteroid-invasion.blogspot.com</p><p>http://www.solvengineer.com/asteroid-invasion.html </p><p> </p> </div>

 

[tap_sa]

<font color="yellow">"Liquid methane has a density of 0.433 kg per liter. Ethanol is much denser at 0.789 kg per liter. Therefore ethanol only occupies 55% of the volume that an equal mass of liquid methane occupies. Ethanol only takes up half the space of methane. "</font><br /><br />Add in the oxidizer with proper mixture ratio and the result is that methane/LOX overall <i>propellant</i> density is about 830kg/m³ while alcohol/LOX is around 1100kg/m³. So ethanol is denser but not that much denser, the depicted SM for lunar trips is way too small.<br /><br />General note; why the conical aft? It means the interstage between SM and stage behind it has to be much longer ie. more massive.<br /><br />And the two engines really boggles the mind. If the plan is to go with pressurefed hypergolics one would think that Apollo-program etc. proved them to be idiot proof without double engine redundancy. If the plan is to try pressurefed methane/LOX then IMO the only real worry is idiot proof igniters, but why not just add redundant igniters instead of duplicate whole engine?

 

[ace5]

are these two rocket nozzles to be protected by any kind of shields against micrometeoroid impacts?

 

[tap_sa]

<font color="yellow">"I think the reason for 2 engines is the use of existing engines not redundancy."</font><br /><br />Any guesses what existing engine that might be, Shuttle OMS?

 

[propforce]

<font color="yellow">Any guesses what existing engine that might be, Shuttle OMS? </font><br /><br />It all depends on what propellant type <img src="/images/icons/wink.gif" /> <div class="Discussion_UserSignature"> </div>

 

[tap_sa]

D'oh you ruined my cunning plan to find out the propellant choice without directly asking it! <img src="/images/icons/laugh.gif" />

 

[n_kitson]

There's a lumpy block thingy that straddles the base of the cone, below the US flag on the cone. What is this protrusion? Won't it be a hinderance during re-entry?

 

[nacnud]

I think it's an umbilical cover between the CM and SM