RS-68 Engines Considered for the (not so SD)HLV

[spacefire]

http://www.space.com/spacenews/businessmonday_060320.html<br />I guess price is the only thing the RS-68s have going for them. But weren't the proposed throwaway SSMEs going to be cheaper than the ones currently used on the Shuttle?<br /> <div class="Discussion_UserSignature"> <p>http://asteroid-invasion.blogspot.com</p><p>http://www.solvengineer.com/asteroid-invasion.html </p><p> </p> </div>

 

[crix]

Did we already discuss the possible use of RD-180? What are thoughts on this rocket engine? <br /><br /><br />*edit*<br />yup,<br />http://uplink.space.com/showflat.php?Cat=&Board=missions&Number=315339&page=10&view=collapsed&sb=5&o=0&fpart=<br /><br />oops, that's the rd-120 (I'm not concentrating ... always minimizing firefox when i hear someone coming up behind me, hehe)

 

[crix]

What's your opinion on this shuttle_guy?<br /><br />I'd prefer that NASA sacrifice up to 10% peformance if it meant that each flight was ~100million cheaper.

 

[crix]

Rightfully so.<br /><br />Yeah I guess we'll have to wait for the results of the studies. If we go with the RS-68s and end up changing the diameter of the craft it seems like we're effectively making this a clean sheet core with SRBs attached to the side.

 

[mikejz]

I thought they stopped manufacturing them already?

 

[crix]

On the front page article they mention that because the RS-68 consumes more 'fuel' they would need to increase the height the of the core (stack? i'm not straight on my terminology..). If more height is needed than is available it was suggested that the diameter be increased.

 

[chriscdc]

The space.com article said that due to the lower ISP they would need more fuel which meant getting taller or wider. They seemed to think getting taller wasn't the way to go.<br />

 

[mikejz]

I wondering if there are any proposals to increase the ISP of the RS-68 or J-2?

 

[mikejz]

I know that the current proposal states that making a 4-SRB SDHLV was ruled out as too costly: What amount are they thinking about in terms of the cost for pad modifications and per-flight costs?

 

[propforce]

<i>".... I wondering if there are any proposals to increase the ISP of the RS-68 or J-2? ..."</i><br /><br />The simple answer is "yes" but I can't tell you the specifics. The ESAS study already hinted an 'upgraded' J-2, now called a J-2X, but that could just be a J-2S with a bigger nozzle. Manufacturing wise, this will essentially be a brand new engine using updated manufacturing processes including some of the RS-68 processes. <br /><br />The RS-68 is being studied for upgrades as well, such as a regen chamber and new injectors, etc. But there will certainly be other upgrade as well for the CaLV. <br /> <div class="Discussion_UserSignature"> </div>

 

[mikejz]

As an aside: Is there current ground support/storage tanks large enought to handle the amount of LOX/LH2 that are needed for HLV?

 

[mattblack]

I've done some rough back-of-the-envelope calculations(!!): If the RS-68s were upgraded in ISP by 5%percent, thrust by 7-9%percent, and the corestage stretched (not fattened) by 5%percent, the CaLV you'd end up with would be 372 feet high. Also, by reducing the parking/assembly orbit to 150 nautical miles (instead of 160) the end LEO payload result should be in the range of 116 tons. Not 124.6 as outlined in ESAS. And this would be using 3x RS-68s, not four as some people suggest. Four might stretch the corestage height to 380+plus feet. With the supporting umbilical tower; would this make it too tall for the VAB?<br /><br />Over at Nasaspaceflight.com, the cost figure bandied about there for RS-68 is $14 million per engine. Would the resultant savings of $100-to-$120 million per flight be worth losing 9 tons of payload, which is critical? <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>

 

[mattblack]

Now they're talking $20 million for disposable SSMEs. If that were true, IF, the RS-68 use would be illogical.<br /><br />http://forum.nasaspaceflight.com/forums/thread-view.asp?tid=581&start=16&posts=27<br /><br />And all this bloody speculation because of funding!! Sheesh, let's not nickel-and-dime a Return to the Moon for the sake of a 'few' million bucks!!<br /> <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>

 

[propforce]

<font color="yellow">Now they're talking $20 million for disposable SSMEs. If that were true, IF, the RS-68 use would be illogical. </font><br /><br />The key question to ask is what is the development cost for this<i> "... $20 million disposable SSMEs..."</i>, as well as what are the risk to schedule ???<br /><br />Also, can Rocketdyne afford to have 2 engine development efforts going on at the same time (SSME and J-2) ??? <div class="Discussion_UserSignature"> </div>

 

[edkyle98]

I very much doubt that an SSME could be built for <br />only $20 million. They cost $38 million just to build <br />in 1989. That's $60 million today.<br /><br /> - Ed Kyle

 

[josh_simonson]

>or was it about saving jobs? <br /><br />Most likely.

 

[propforce]

<font color="yellow">If the tank needs to be redesigned then we don't have a "shuttle derived" anything. Wasn't the whole point to use as much Shuttle infrastructure as possible?</font><br /><br />First of all, the CaLV will not start for another 10 years so nothing will be decided in a hurry. Second; you bet the tank will have to be redesigned as the CaLV core stage. The load on the tank would certainly be different than being an ET, with the EDS & payload sitting on top and with engine pushing from the bottom.<br /><br />But assuming it still keeps the same ET diameter, then the "shuttle derived" still hold with the use of same tooliings, people and facilities. <br /><br /><font color="yellow">Wasn't using all this Shuttle infrastructure about saving money, or was it about saving jobs? </font><br /><br />Wake up! This is NASA! It's not about saving money. Government projects are not about being profitable. If it is, why not use one of the EELV contractors for CLV and eliminate 90% of the current shuttle workforce? But if you do that, then most of people at NASA MSFC, GRC, and KSC will have very little to do. It's all about national pride, american technological leadership, and yes, jobs jobs jobs (... and congressional district jobs so to get the right supports). <div class="Discussion_UserSignature"> </div>

 

[mikejz]

By the time the SDHLV flies, its core shuttle components (ET Design, SRBs, SSME(Maybe) Will be pushing 50 year old designs. So much for technological leadership, eh?

 

[propforce]

<font color="yellow">By the time the SDHLV flies, its core shuttle components (ET Design, SRBs, SSME(Maybe) Will be pushing 50 year old designs. So much for technological leadership, eh? </font><br /><br />(....Waving my fist in the air....) Sacarsm will get you nowhere youngman !!! <img src="/images/icons/smile.gif" /><br /><br />Now just because it will look like an ET doesn't mean it will be the same ET. We may have develop nanotechnology enough to apply them to all these components, for example. <br /><br />Besides, unless the Chinese get to the Moon before we do, we are in no hurry to get there. (I said this as a sad sacarstic remark) <div class="Discussion_UserSignature"> </div>

 

[edkyle98]

"... can Rocketdyne afford to have 2 engine development efforts going on at the same time (SSME and J-2) ??? "<br /><br />No, because Rocketdyne no longer exists. <img src="/images/icons/wink.gif" /> <br /><br />Its remnants are part of Pratt & Whitney Rocketdyne <br />(PWR) now. PWR won't spend a dime to develop <br />these engines. Someone at NASA will to have to write <br />a big check first. <br /><br />No bucks, no thrust.<br /><br /> - Ed Kyle

 

[mikejz]

The entire concept of the SDHLV is to reduce the need for said technological innovation. Hence the whole 'Shuttle Derived' business. <br /><br />There are already plenty of innovations in engine design and materials that the SDHLV is not incorporating. If it does not incorporate advancements that have already been made, why do you think they would incorporate innovations in the future?

 

[rybanis]

Heres a quick question:<br /><br />Why do restartable engines have to wait a certain amount of time before restarting? Do they have to cool down for a bit? <div class="Discussion_UserSignature"> </div>

 

[rybanis]

Can the ET handle the stress of being the core of the booster? I didn't know it was that strong. <div class="Discussion_UserSignature"> </div>

 

[rybanis]

Oh, well that makes sense. <div class="Discussion_UserSignature"> </div>

 

[propforce]

<i><font color="yellow">"Why do restartable engines have to wait a certain amount of time before restarting? " </font>/i><br /><br />On some engines, such as the SSME, it's almost impossible to re-start on the same flight. That's because it uses "pre-burners" which is basically low temperature combustors to create hot gases to drive the turbopumps. These hot gases contain water (steam) which would need to be expelled (dried) before engine chilldown could begin so no ice can block injector passages. Some crevices are so small that increase purge flow rate does not help speeding up the drying time.</i> <div class="Discussion_UserSignature"> </div>