Lockheed Martin's CEV is winged!!

[henryhallam]

<font color="yellow"><br />The Apollo CM could probably have skipped -- they just had no need to.<br /></font><br /><br />Indeed it was designed with that capability, AGC programs P65 and P66 were available to handle a "skip-out" trajectory. This technique could be used to extend the range from initial entry to splashdown by as much as 2000km, at the expense of some landing accuracy. <br /><br />AFAIK they were never used on an actual mission.

 

[henryhallam]

<font color="yellow"><br />Wrong. There are a couple of means of getting 'more chances'. One is to skip off the atmosphere to bleed off speed. You can also use a propellant burn to circularize your orbit around Earth. Or a combination of the two.</font><br />Actually capture by rocket into LEO from a lunar return trajectory is prohibitively expensive in terms of dV. You could aerocapture into LEO but this would require a heatshield or TPS with nearly the same capability as that needed for a proper re-entry. If you were in that situation you would want a heatshield capable of full re-entry anyway in case guidance fails and you don't manage to skip back out again. After aerocapture when you are at apogee you would need to make a small burn to raise your perigee back out of the atmosphere.

 

[larper]

<blockquote><font class="small">In reply to:</font><hr /><p>I expect the heating loads on a direct re-entry from a Mars return would be high enough to make that 'a bad idea'<p><hr /></p></p></blockquote><br />Is the reentry velocity between the two that much different? I wouldn't think so. Coming in from Lunar orbit is pretty close to escape velocity. The step up from Lunar return velocity to Mars return velocity is much smaller than the step from LEO to lunar. <div class="Discussion_UserSignature"> <p><strong><font color="#ff0000">Vote </font><font color="#3366ff">Libertarian</font></strong></p> </div>

 

[mrmorris]

<font color="yellow">"Is the reentry velocity between the two that much different?"</font><br /><br />Dunno. That's is spacester's area of expertise -- not mine. I could make some *very* ugly approximation calculations (i.e. Earth to Moon took three days -- that was 'X' distance -- compare that to distance from Earth-to-Mars, etc.). However -- the margin of error would likely be so large as to generate useless data.

 

[henryhallam]

<font color="yellow">Is the reentry velocity between the two that much different?</font><br /><br />I will run a sim. with Orbiter, check back in an hour or two.

 

[spacester]

<font color="yellow">Actually capture by rocket into LEO from a lunar return trajectory is prohibitively expensive in terms of dV.</font><br /><br />It certainly is expensive, but I believe it is a premature conclusion to say that is it prohibitively expensive. Certainly a strong case can be made in the "old school" way of doing things.<br /><br />But if we have orbital re-prop available, it may very well turn out that it's entirely worth it to go from moon to LEO in order to take advantage of the infrastructure you've created to support that approach. <div class="Discussion_UserSignature"> </div>

 

[spacester]

Don't count on me for everything dV. I appreciate the nod, but I don't have all the answers by any means. Use that Orbiter program - I'd be using it myself but I'm kinda "between computers" these days. I'm just glad there is now a way for folks to run some scenarios like for the question at hand.<br /><br />Truth is, I've never gotten fully up to speed on CisLunar trajectories. Ironic, cuz my first love is a Lunar Dome and I need to figger out the dV side of things to build it. <div class="Discussion_UserSignature"> </div>

 

[mrmorris]

<font color="yellow">"Use that Orbiter program"</font><br /><br />Never used it -- orbital mechanics isn't really that exciting to me. <img src="/images/icons/smile.gif" /><br /><br /><font color="yellow">"Truth is, I've never gotten fully up to speed on CisLunar trajectories."</font><br /><br />I could look up the velocity the Apollos returned at. I figured you'd know a Mars return velocity off the top of your head. <img src="/images/icons/smile.gif" />

 

[mrmorris]

OK -- so I'll look it up... Via my friend Google, I found this regarding Apollo:<br /><br /><i>"On reaching Earth, the command module alone will reenter the atmosphere at a velocity of about 36000 feet per second, some 11000 fps faster than reentry from Earth orbit."</i><br /><br />That equates to ~24,545 mph for a lunar return and ~17,045 mph for a return from LEO. Pretty spot on for SG's WAG.<br /><br />I had less luck finding a value for a Mars return, which is what I expected. I found the perfect article for it, but unfortunately, it's not free, and I'm just not interested enough to pay $25 for it. It's available at the AIAA site: Survey of velocity requirements and reentry flight mechanics for manned mars missions. You can view the first page, and in it they talk about the propulsive requirements for various Mars missions, but don't specifically give the re-entry velocity. Looks like it'd be an interesting read, though.

 

[larper]

Reentry from Mars return would be so close to escape velocity that any difference would be meaningless. Escape velocity is about 25,000 mph. <br /><br />So, reentry from Lunar return is virtually the same as from Mars return. An Apollo heat shield should work just fine. No "skipping" required.<br /> <div class="Discussion_UserSignature"> <p><strong><font color="#ff0000">Vote </font><font color="#3366ff">Libertarian</font></strong></p> </div>

 

[mrmorris]

<font color="yellow">"So, reentry from Lunar return is virtually the same as from Mars return."</font><br /><br />I'm not disputing that may be the case. I'd just like to see a model, or documentation from NASA, the Ruskies, etc. that says re-entry velocity from a Manned Mars mission will be about... There's a whole lot of opinions tossed around on the board in the guise of facts. I'm just really fond of accountability.

 

[spacefire]

not exactly-Apollo Reentry-24545mi/hr<br />reentry from a Hohman flight from Mars-31988mi/hr<br /><br /><font color="purple">A more accurate calculation gives 459 days (ours contains approximations). When the return rocket arrives at Earth, it will be overtaking it, since its velocity V1 is exceeds the orbital velocity V0 of Earth by about 3 km/s. Before safely descending to the ground, the spacecraft also must get rid of the velocity v0 given to it by the pull of the Earth, about 11.3 km/s. However, if it reenters by skimming the atmosphere "just right," its extra kinetic energy will safely dissipate as heat, with no need for more rocket firings. <br /></font>/safety_wrapper> <div class="Discussion_UserSignature"> <p>http://asteroid-invasion.blogspot.com</p><p>http://www.solvengineer.com/asteroid-invasion.html </p><p> </p> </div>

 

[rybanis]

This thread is gigantic and cannot be stopped. I'm having a hard time keeping up! <div class="Discussion_UserSignature"> </div>

 

[spacefire]

made comet on this thread <img src="/images/icons/smile.gif" /> <br />these forums are cool. <div class="Discussion_UserSignature"> <p>http://asteroid-invasion.blogspot.com</p><p>http://www.solvengineer.com/asteroid-invasion.html </p><p> </p> </div>

 

[larper]

<blockquote><font class="small">In reply to:</font><hr /><p>reentry from a Hohman flight from Mars-31988mi/hr <p><hr /></p></p></blockquote><br />Hmm. Right. You aren't falling toward the earth, you are falling toward the sun, and the earth just gets in the way. My mistake. <div class="Discussion_UserSignature"> <p><strong><font color="#ff0000">Vote </font><font color="#3366ff">Libertarian</font></strong></p> </div>

 

[spacefire]

yeah, your orbit is an ellipse tangent to both Mars' and Earth' orbits<br /><br />here's the website I took the information from:<br /><br />http://www.phy6.org/stargaze/Smars3.htm <div class="Discussion_UserSignature"> <p>http://asteroid-invasion.blogspot.com</p><p>http://www.solvengineer.com/asteroid-invasion.html </p><p> </p> </div>

 

[starfhury]

I've been reading about the new t/Space proposal and it makes a lot of sense in this case to use a capsule. Their proposal has dispelled my objections over using the capsule design in the CEV by totally separating out functionality. The capsule will be used purely as a method for sending and returning 4 - 6 people from orbit perferably the ISS. Used strictly in this fashion, the lower development costs of the capsule offers certain advantages. Used as the basis of the entire CEV VSE program my original objects over using the capsule design still stands. <div class="Discussion_UserSignature"> </div>

 

[jurgens]

I think they should develop a non reusable capsule at first, but later on move to a completely resuable lifting body/Capsule design for Earth-LEO.

 

[gunsandrockets]

two other noteworthy things about the Lockheed CEV<br /><br />It's bi-prop engines burn alcohol. I wonder if XCOR Aerospace can put in a bid for that engine? XCOR is the only company I know of that has an alcohol burning engine in stock.<br /><br />Plus there is a couple of mysterious areas in the CEV, one is marked "Active Thermal Control" and the other is "multi-fluid evaporative system". I wonder if Lockheed is using active as well as passive thermal protection during re-entry?<br /><br />Shortly before Rotary Rocket went under, I listened to one of thier engineers talk about an active thermal protection system utilising water for their spacecraft. Maybe Lockheed is thinking the same way. How about using remaining fuel as a heat sink which is then dumped? I know that once upon a time the XB-70's fuel was used an an active cooling agent for the airframe.

 

[najab]

><i>This thread is gigantic and cannot be stopped. I'm having a hard time keeping up! </i><p>Yup, it is kinda big. Guess it's time to break it...</p>