Lockheed Martin's CEV has two rocket engines

[tap_sa]

I concur. Apollos had similar bulge. It turns aside and stays with the SM when CM is released for reentry.

 

[rybanis]

<blockquote><font class="small">In reply to:</font><hr /><p><br />"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? "<br /><br />That is the CM/SM umbilical which remains with the SM. <p><hr /></p></p></blockquote><br /><br />Was that umblilical the only interface between the CM/SM on Apollo? <div class="Discussion_UserSignature"> </div>

 

[rybanis]

That must have been a very packed umbilical. <div class="Discussion_UserSignature"> </div>

 

[mlorrey]

I will place a bet here and now that those engines are running on helium chilled monatomic hydrogen (1000s Isp) or else some high density fuels like quadricyclane, etc.<br /><br />Using LOX/LH2, the SM is too small. With denser hydrocarbons, it isn't.

 

[propforce]

<font color="yellow">"I will place a bet here and now that those engines are running on helium chilled monatomic hydrogen (1000s Isp) or else some high density fuels like quadricyclane, etc." <br /><br />I will take that bet !! </font><br /><br />ME TOO! I need beer money !! <img src="/images/icons/smile.gif" /><br /><br />Besides, metallic hydrogen would be much denser thus more compact.<br /><br />BTW, quadricyclane development has run into a snag, the development work has stopped. It's Isp is less than that of methane. The PI has left the AFRL. <div class="Discussion_UserSignature"> </div>

 

[mlorrey]

Well, I didn't say just quadricyclane, it was an example. Seeing the commentary about ethanol, it appears I was right. Cubane is another high energy high density possibility.<br /><br />Then of course, there is also always boron.... <img src="/images/icons/wink.gif" />

 

[propforce]

<font color="yellow">Then of course, there is also always boron.... </font><br /><br />SIGH... you remind me of the unobtanium days... <img src="/images/icons/laugh.gif" /> <div class="Discussion_UserSignature"> </div>

 

[mlorrey]

Actually, I've confirmed all of my earlier assertions about boron additives. The NASA HEDM program have tested RP-1/boron slurries with LOX and confirmed pretty much what I had expected, with high concentrations getting Isp as high as 650 sec.

 

[propforce]

Please provide link to the NASA HEDM test program. <div class="Discussion_UserSignature"> </div>

 

[mlorrey]

http://sbir.grc.nasa.gov/launch/foctopsb.htm<br /><br />There is a lot of reading here.

 

[j05h]

aren't those mixtures explosive and toxic? (sorry, haven't read link) We discussed boron, flourine something-or-other and several other exotic fuels on sci.space.policy over the years, if you want further info. Lots of exotic-fuel tests in the 50's and 60's, with a steady march toward safer fuels in the world's rockets. <br /><br />The Isp is impressive, and fits the square-jawed fighter pilot image, but isn't going to prove practical for a space transport system, IMHO. Exotic fuels are dangerous, and handling becomes a serious issue. It doesn't seem like the right path to a "CATS" system. For CEV I think they need to at least make a nod toward in-situ fueling, as well. <br /><br />Oh, and that dual-chamber motor on the CEV graphic is an RD-180 or derivative:<br /><br />http://www.spaceandtech.com/spacedata/engines/rd180_sum.shtml<br /><br />Josh <div class="Discussion_UserSignature"> <div align="center"><em>We need a first generation of pioneers.</em><br /></div> </div>

 

[gunsandrockets]

"I believe [the SM is too short], however the cone shape coming out of the bottom center of the SM could make up for the short SM."<br /><br />You say this CEV's SM looks too small. But does it really? Even though it looks stubby, when carefully analyzed this SM actually has all the volume it needs. I just think we are all too used to seeing the old Apollo CSM and that accounts for the illusion.<br /><br />By my crude reckoning the dimensions of the Apollo SM (minus the engine bell) are of 3.9 meters in diameter and 4.6 meters in length. Within this volume is contained roughly 24 tonnes of structure, equipment, consumables and propellent.<br /><br />The CEV SM, according to the latest info from NASA, will have a maximum diameter of 5 meters and mass roughly 13 tonnes. So just how long a cylindrical body would that SM need to contain that much mass? And how stubby is that length compared to the 5 meter diameter of the SM?<br /><br />According to my calculations the CEV SM could be as stubby as only 1.5 meters long. That length is less than 1/3 of the diameter. Talk about stubby! So the artistic illustration of the Lockheed-Martin CEV is entirely consistent with a SM which contains enough propellent for 1.7 km/s delta V.<br /><br />Now of course there are other factors which alter the appearance. Such as the SM needs more space for consumables to support the CEV's larger 4 man lunar crew. But the SM would also be smaller because of the lack of any fuel cells. Methane/LOX is a bulkier propellent than storables, but then the Lockheed-Martin CEV may use ethane/LOX or even storables. So unless this SM uses LH2/LOX, all these various factors would not that greatly change the basic stubby look of the CEV's SM. <br />

 

[gunsandrockets]

"Oh, and that dual-chamber motor on the CEV graphic is an RD-180 or derivative:"<br /><br />You can't be serious.<br /><br />The Apollo SM used a 20,000 pounds of thrust engine to maneuver a mass of 45 tonnes (during LOC). <br /><br />Why would the 23 tonne CEV need a rocket engine with 860,000 pounds of thrust! <br />

 

[gunsandrockets]

"I will place a bet here and now that those engines are running on helium chilled monatomic hydrogen (1000s Isp) or else some high density fuels like quadricyclane, etc."<br /><br />Oh, yeah. I'll take that bet! If NASA was concerned about program delay by using methane, why would NASA switch to some even more exotic propellent? That doesn't make any sense. <br /><br /><br />

 

[rybanis]

He was joking. <div class="Discussion_UserSignature"> </div>

 

[tap_sa]

<font color="yellow">"There is a lot of reading here."</font><br /><br />Indeed, thanks for the great link!<br /><br />But could you provide link to the paper about 650s RP-1/boron slurry test? I rushed through the site at didn't find such, closest was about estimations how atomic boron suspended in liquid helium might work.

 

[j05h]

"or derivative" gives me a little wiggle room! 8) My guess is that the graphic artist, knowing he was working for Lockmart, put their Atlas engine on the CEV model and it passed inspection. It's a completely reasonable mistake from an arts/marketting standpoint. I didn't say anything about it being flightworthy, just what the model was obviously taken from. <br /><br />Josh <div class="Discussion_UserSignature"> <div align="center"><em>We need a first generation of pioneers.</em><br /></div> </div>

 

[nacnud]

Or perhaps the artist scaled the SM from the lifting body CEV SM

 

[gunsandrockets]

"However the CEV SM must carry a lot more propellant than the Apollo did. "<br /><br />Uh, no. Not according to anything NASA has said so far about the CEV.<br /><br />The Apolllo SM massed 24 tonnes. The CEV SM masses about 13 tonnes. And for good reason. The CEV only has to push it's own mass of 23 tonnes for TEI. The Apollo SM had to conduct LOC for the entire 45 tonne CSM and LM stack plus push the remaining CSM mass for TEI. There is just no comparison between the two.<br /><br />In fact according to an interview of Faget, the CSM is actually sized for enough propellent for direct launch to Earth from the surface of the moon! (assuming of course it begins fully fueled)

 

[josh_simonson]

Atomic Boron<br />Boron performance is high, over 600 seconds for many cases. Figure 3 shows the map of Isp values. A peak<br />monopropellant performance of 689 seconds is delivered at a 60-wt% of B atoms. At a 50-wt% atom loading, the<br />Isp value was 651 s. Adding O2 as an oxidizer did not increase the 50- and 60-wt% atomic B Isp over the monopropellant<br />cases.<br />At 22-wt%, the Isp does increase with the addition of O2. In Figure 4, the addition of He to the propellant (at an<br />atom loading of 22-wt%) showed that a peak Isp value occurs at an O/F of 0.5. The monopropellant Isp, sans He,<br />was 436 s, whereas with an O/F at 0.5, the Isp ranged from 530 s (10-wt% He) to 473 s (40-wt% He). Figure 5<br />shows the effect of He with a 50-wt% B cases. At this high atom loading, the He has only a small effect on the<br />rocket Isp.<br /><br /><br /><br />Something like this is far from applicability, and may never be safe enough to use around people. Atomic boron has nothing to do with the borane fuel that was developed for valkyrie.<br /><br />Boron isn't especially toxic (it's a required trace nutrient for humans and plants), but it can poison plants in large quantities. Probably a boron rocket traveling over the ocean would be acceptable because the boron would be diluted.<br />

 

[gunsandrockets]

"My guess is that the graphic artist, knowing he was working for Lockmart, put their Atlas engine on the CEV model and it passed inspection. It's a completely reasonable mistake from an arts/marketting standpoint. I didn't say anything about it being flightworthy, just what the model was obviously taken from. "<br /><br />I don't think you are being fair to the artist. If you take a close look at that drawing you can see the expansion nozzles are huge compared to the thrust chambers. That is characteristic of low-thrust high-ISP engines designed for the vacuum-condition high-altitude operations of upper stage rockets. Not characteristic of the RD-180.

 

[gunsandrockets]

"Atomic boron has nothing to do with the borane fuel that was developed for valkyrie. "<br /><br />Aside from present-day experiments on metastable propellents (some of which use liquid helium for storage. yikes! talk about cryogenic difficulties), the earlier boron fuels developed in the 1950's seem to have proved impractical for rocket engine applications. I've found some information on the web talking about this...<br /><br />http://www.chem.ucla.edu/dept/Faculty/hawthorne/lecture/lecture2.htm<br /><br />"The rocket fuel program floundered. The problem was that the solid boron oxides present in the combustion products of the rocket motor, interfered with the expected thermodynamics. So boranes were not super fuels for rockets and that program was dropped."<br /><br />If boron oxide solids were condensing out of the hot gas flow of the rocket, how much of that problem would it take to ruin the potential ISP of boron fuels? Not much I think.

 

[j05h]

>Or perhaps the artist scaled the SM from the lifting body CEV SM<br /><br />nac, others - I stand by my earlier asssertion. It's an artist's mistake, he used "our engine" instead of the competitors for the CEV viewgraphs. Not sure what Lockmart will actually use for CEV, but it won't be a competitor's product. eh, I was hoping Pratt&Whitney's webpage would have a "look-alike" option that I hadn't seen previously, but I can't find any candidate engines quickly. <br /><br />Josh <div class="Discussion_UserSignature"> <div align="center"><em>We need a first generation of pioneers.</em><br /></div> </div>

 

[j05h]

SG- i was following my "looks like RD180" hunch to see if it was P&W. Any hints on the engine provider? 8)<br /><br />Josh <div class="Discussion_UserSignature"> <div align="center"><em>We need a first generation of pioneers.</em><br /></div> </div>

 

[gunsandrockets]

"It's hypergolic, but the Apollo Lunar Descent Engine would be about right if paired...?"<br /><br />Hmmm...LM mass 15 tonnes, CEV mass 23 tonnes, so your theory sounds plausible.<br /><br />During the Apollo 13 emergency, how many times and over what time separation was the LM descent engine fired? I'm wondering because of something I read in the book, "Chariots for Apollo."<br /><br />As I recall, the book described the LM descent engine having limited resistance to the corrosive propellent. Supposedly the thinking was the descent engine would only be used during a single event, the landing on the moon, so it didn't need longer term durability.<br /><br />If that's true such an engine would not be suited for the CEV since the CEV needs an engine able to fire multiple times, separated by periods as great as sixth months.<br /><br />