Aren't SSME's too expensive to be disposable?

[vogon13]

What were we talking about?<br /><br /> <div class="Discussion_UserSignature"> <p><font color="#ff0000"><strong>TPTB went to Dallas and all I got was Plucked !!</strong></font></p><p><font color="#339966"><strong>So many people, so few recipes !!</strong></font></p><p><font color="#0000ff"><strong>Let's clean up this stinkhole !!</strong></font> </p> </div>

 

[drwayne]

For some reason I'm reminded of a late uncle, who told me late in his life, "Wayne, at my age, the highlight of my day is a really good bowel movement".<br /><br />I have read a fair amount about stuff they have tried running through an RL-10 - it is a very useful testbed.<br /><br />Wayne <div class="Discussion_UserSignature"> <p>"1) Give no quarter; 2) Take no prisoners; 3) Sink everything."  Admiral Jackie Fisher</p> </div>

 

[vogon13]

My granny had a key chain that said:<br /><br />Doxidan in the AM<br /><br />For a BM in the PM<br /><br /><br />LOL!<br /><br /><br /> <div class="Discussion_UserSignature"> <p><font color="#ff0000"><strong>TPTB went to Dallas and all I got was Plucked !!</strong></font></p><p><font color="#339966"><strong>So many people, so few recipes !!</strong></font></p><p><font color="#0000ff"><strong>Let's clean up this stinkhole !!</strong></font> </p> </div>

 

[vogon13]

You know, if this triggers a tasteful (yet at the same time disturbing) thread over in Human Biology, Admin will be mortified with us.<br /><br /><br /><img src="/images/icons/wink.gif" /><br /><br /><br /> <div class="Discussion_UserSignature"> <p><font color="#ff0000"><strong>TPTB went to Dallas and all I got was Plucked !!</strong></font></p><p><font color="#339966"><strong>So many people, so few recipes !!</strong></font></p><p><font color="#0000ff"><strong>Let's clean up this stinkhole !!</strong></font> </p> </div>

 

[drwayne]

Doxidan - hmmm, I forgot that - they had some funy commercials some years ago - quite a few now actually.<br /><br />Wayne <div class="Discussion_UserSignature"> <p>"1) Give no quarter; 2) Take no prisoners; 3) Sink everything."  Admiral Jackie Fisher</p> </div>

 

[vogon13]

Sigh, I can't believe I said 'tasteful' in that regard......<br /><br /><br /><img src="/images/icons/tongue.gif" /><br /><br /><br /> <div class="Discussion_UserSignature"> <p><font color="#ff0000"><strong>TPTB went to Dallas and all I got was Plucked !!</strong></font></p><p><font color="#339966"><strong>So many people, so few recipes !!</strong></font></p><p><font color="#0000ff"><strong>Let's clean up this stinkhole !!</strong></font> </p> </div>

 

[propforce]

<i>"... It wasn't a RS-68 but an RL-10-B2 ignition test with densified LH2. ..."</i><br /><br />OK that makes more sense. Yes I am aware of such test. I talked to Mark Haberbusch about this test in 1998. <br /><br />Unfortunately IMO, RL10 engine cycle makes it a poor choice to demonstrate densified propellant performance gain. A GG or a SC cycle engine, such as the RS-68 or the SSME, could benefit more from densified propellant. Also, to truly realize this gain, an engine's turbopumps as well as engine flow balance needed to be modified in order to realize the benefit of densified propellant. <br /><br />But the biggest benefit is to minimize boil-off propellant, particular the hydrogen, from a vehicle perspective. So this could potentially save hundreds of pounds of unusable hydrogen -- all which can be translated into payload performance gain.<br /><br />I think it's a topic that worth a further investigation, particularly with the long duration mission such as lunar/ mars exploration where propellant boil-off is a major concern. <div class="Discussion_UserSignature"> </div>

 

[rybanis]

Now, I've read over this thread, and I find it very interesting, but I have one question:<br /><br />How do you make a SSME disposable? I mean, what is in the SSME design that can be taken out/modified to make the engine cheaper, but not crazy unreliable?<br /><br /><br />I'm also wondering how they will pull off an air-start SSME for the upper stage. <div class="Discussion_UserSignature"> </div>

 

[propforce]

<i>".... How do you make a SSME disposable?..."</i><br /><br />By making the Indian Ocean one giant trash can? <img src="/images/icons/smile.gif" /><br /><br />The details is entirely upto NASA and Rocketdyne (now part of Pratt & Whitney) of course. For starter, I would venture to <i>guess </i> that means to take the design life out of the engine, that maybe replacing costly parts with a cheaper manufactured parts. For example, replacing the tube-wall nozzle with channel-wall nozzle manufacturing technique, and replacing the existing main combustion chamber (MCC) manufacturing process with the RS-68 process, simplified cast parts turbopumps, etc. Sacrifice engine weight and performance for cost.<br /><br /><br /><i>"......I'm also wondering how they will pull off an air-start SSME for the upper stage. ..."</i><br /><br />Oh you mean that is a requirement??? That will cost an extra $20M per engine <img src="/images/icons/wink.gif" /><br /><br />That's why companies get paid big bucks in this business (notice I did not say engineers get paid big bucks - just give us an interesting project and we'll work for peanut butter sandwiches). <br /><br />Either thick-wall ET and lots of helium, or start the engine before separating from the SRB, are two immediate but unlikely potential solutions come to mind. <br /><br /><br /> <div class="Discussion_UserSignature"> </div>

 

[rybanis]

I dunno, I kind of always imagined air-start rocket engines as being fast to get up to full thrust. The SSME...its just hard to imagine! Heh. <div class="Discussion_UserSignature"> </div>

 

[drwayne]

"I kind of always imagined air-start rocket engines as being fast to get up to full thrust."<br /><br />I am curious, why would you say that - what mechansm are you thinking about that would make it faster to come to full thrust?<br /><br />Wayne <div class="Discussion_UserSignature"> <p>"1) Give no quarter; 2) Take no prisoners; 3) Sink everything."  Admiral Jackie Fisher</p> </div>

 

[propforce]

<i>"..... I dunno, I kind of always imagined air-start rocket engines as being fast to get up to full thrust. The SSME...its just hard to imagine! Heh. ..."</i><br /><br />Rocketdyne will have its hands full on this one for sure. Personally I question the SRB choice as 1st stage as well as SSME as 2nd stage engine, but not many U.S. engine options available. I can only assume that NASA does not want to get into another engine development program on this one.<br /><br />For one thing, you can't have an engine abort command for a 2nd stage engine !! <br /><br /> <div class="Discussion_UserSignature"> </div>

 

[barrykirk]

How do you densify LH2 and LOX?

 

[propforce]

<i>"... How do you densify LH2 and LOX? ..."</i><br /><br />By cooling them to below their normal boiling point, e.g., sub-cooled liquid. <div class="Discussion_UserSignature"> </div>

 

[vogon13]

LH2 can be chilled to form 'slush', phase change let's you get more molecules in the tank.<br /><br />(not all materials expand when frozen like water)<br /><br /><br />IIRC, if it could be somehow stabilized, LH1 would be even better, but much more dangerous, as it would tend to form LH2 dramatically.<br /><br /><br /><br /> <div class="Discussion_UserSignature"> <p><font color="#ff0000"><strong>TPTB went to Dallas and all I got was Plucked !!</strong></font></p><p><font color="#339966"><strong>So many people, so few recipes !!</strong></font></p><p><font color="#0000ff"><strong>Let's clean up this stinkhole !!</strong></font> </p> </div>

 

[barrykirk]

Well, I read the above article and now I know.<br /><br />That is important, because one of the biggest advantages of RP-1 and other hydrocarbon based fuels over LH2 is density.

 

[barrykirk]

Not to mention it would liberate a great deal of heat getting rid of the L portion of LH

 

[barrykirk]

Actually, LH1 would be going the wrong way. It would be even less dense than LH2. And the final exhaust product would still be steam. Unless you were going to have an exhaust of LH2. That could get really complicated.

 

[propforce]

<i>"....Unless you were going to have an exhaust of LH2. That could get really complicated. ..."</i><br /><br />Actually that would be really easy, I think it's called "leak'.<br /><br />There would be no combustion in that case, can't get much thrust out of that one. <div class="Discussion_UserSignature"> </div>

 

[vogon13]

<br />The exhaust would be hotter steam.<br /><br />The chemical binding energy of the H2 would be available in the combustion chamber in the case of H1. More zap, more go. Spontaneous release in the fuel tank as H1 forms H2 would ruin your day, though.<br /><br />Best oxidizer would similarly be F1 over F2, and yes, the danger would be even worse in this scenario.<br /><br /> <div class="Discussion_UserSignature"> <p><font color="#ff0000"><strong>TPTB went to Dallas and all I got was Plucked !!</strong></font></p><p><font color="#339966"><strong>So many people, so few recipes !!</strong></font></p><p><font color="#0000ff"><strong>Let's clean up this stinkhole !!</strong></font> </p> </div>

 

[barrykirk]

Not to mention the environmental people would have their panty's in a wad over HF exhaust.<br /><br />But seriously, the SSME is already running so hot that you are at the very limits of material tech to keep the engine from melting while in use.<br /><br />Higher temperatures would be a real engineering difficulty. Not to mention the other problem you talked about earlier. I would not want to ride on that rocket.

 

[vogon13]

HF exhaust would be a little rough on the launch facilities too. You think salt spray is corrosive on exposed steel gantries.....<br /><br /><img src="/images/icons/tongue.gif" /><br /><br /><br /><br /> <div class="Discussion_UserSignature"> <p><font color="#ff0000"><strong>TPTB went to Dallas and all I got was Plucked !!</strong></font></p><p><font color="#339966"><strong>So many people, so few recipes !!</strong></font></p><p><font color="#0000ff"><strong>Let's clean up this stinkhole !!</strong></font> </p> </div>

 

[propforce]

<i>"... HF exhaust would be a little rough on the launch facilities too. You think salt spray is corrosive on exposed steel gantries..... "</i><br /><br />Not if the entire launch pad is made of PTFE !! <img src="/images/icons/laugh.gif" /> <div class="Discussion_UserSignature"> </div>

 

[vogon13]

300 foot tall plastic tower gantry would not respond well to the hot rocket exhaust.<br /><br />Big puddle of melted sticky goo. Giant glue trap for Florida gators till it solidified.<br /><br /><br />{now PETA is PO'd}<br /><br /><br /><img src="/images/icons/wink.gif" /><br /><br /><br /><br /><br /><br /> <div class="Discussion_UserSignature"> <p><font color="#ff0000"><strong>TPTB went to Dallas and all I got was Plucked !!</strong></font></p><p><font color="#339966"><strong>So many people, so few recipes !!</strong></font></p><p><font color="#0000ff"><strong>Let's clean up this stinkhole !!</strong></font> </p> </div>

 

[tap_sa]

Every fluorine rocket launch should be immediately followed by Orion launch. Nice warm nuclear breeze would wipe the gantry clean.