CLV to change

[ragnorak]

<br />It looks like NASA is re-designing ATK's SRB for the first stage of the CEV launch vehicle.<br /><br />This article suggests they are already working on the casing. Any ideas why that would be?<br /><br />http://www.flightinternational.com/Articles/2006/01/17/Navigation/200/204129/Space+Exploration+The+next+big+leap.html<br />

 

[trailrider]

Not sure what he means. According to 'Doc' Horowitz, when he gave his talk at the Mars Society Conference last summer (and I had a chance to ask the specific questions), there is no need to beef up the SRB for the "Stick" configuration as there is less bending moment than is applied during ignition of the SSME's before liftoff. That could, of course, be subject to change, based on a number of things that hadn't been defined yet at that time.<br /><br />At the time I talked with him, I asked about the possibility of thrust-terminating to back the SRM away from the rest of the vehicle. Doc said that would open up a whole can of worms (or words to that effect), since you add the potential for the TT port Safe-And Arms to malfunction, either premature firing or failure to fire. Although using TT on ballistic missile top stages works, don't have the statistical data to prove exactly how reliable it is, and we don't need any more problems. So I'd bet THAT technique is out, as is "fire-in-the-hole" ignition of the 2nd stage engine to push the 1st stage away. (Too much chance of overpressures in the interstage messing up something. I seem to recall that Titan II/Gemini did use FITH, igniting the 2nd stage at the same time that 1st Sep was initiated. NOT sure, as I didn't get involved with Titan on that level.)<br /><br />Besides, the SRM's will still be producing some thrust at tailoff and separation. So the best technique would seem to be using retro-thrust motors.<br /><br />Things that will have to be changed will be the attach points for the interstage on the front end of the SRM (which is the new designation for the SRB); figuring out some means of roll control, probably on the interstage; re-orienting the separation motors pointing forward and outboard (to prevent exhaust impingement on the 2nd stage)...or possibly designing new ones; and determining if fins are needed on the bottom of the SRM to increase attitude command authority. I would also suspect there might b

 

[mikejz]

To do think they will change the 2nd stage to a 2 J-2s or keep the SSME? It seems like keeping the SSME will allow cost saving with economies of scale.

 

[no_way]

whatever happened to safe, simple and soon ?

 

[mikejz]

I mean with not having to have two production lines (J2 and SSME) for HLV. Also having the SSME for the CLV seems to make the HLV an easy political sell.

 

[mikejz]

I mean this.<br /><br />The HLV requrests the SSME<br /><br />If the CLV goes to the J-2 Then there are two production lines instead of one. <br /><br />The point being that if the SSME line is started NOW as opposed to when the HLV is developed (IF it is) It makes the HLV an easier sell. If we already make the SSMEs for the CLV, it makes the threat of cancalling the HLV less.

 

[josh_simonson]

The HLVs earth departure stage uses the J2-s+ as well, so they'll be building the J2s anyway. 2 J2s may give the CLV upper stage engine out capability, if they go that route.

 

[trailrider]

"They have found problems in building in the SSME air start capability."<br /><br />Kind of figured that might be the case. Is that official? I mean is that included in the revised RFP?<br /><br />So does that mean they will go to the J-2 for the CLV 2nd Stage? And what is the difference in development time for the revised J-2's? Is the tooling or at least the drawings still in existance? Or will they have to start from scratch?<br /><br />Ad Luna! Ad Aries! Ad Astra!

 

[josh_simonson]

From http://www.astronautix.com/engines/j2s.htm<br /><br />It was estimated by ATK Thiokol in 2005 that restarting the J-2S program, including engine fabrication, design and reliability verification, certification, and production, would require four years. Although no J-2S tooling was known to exist, modern soft tooling could be developed quickly and less expensively than the original hard tooling. There was an existing manufacturing and supplier network in place to support a J-2S restart. <br /> <br /><br />So presumably they can start flight testing the J-2s around 2009-2010.

 

[propforce]

<font color="yellow"> Delta V for the SM is required to be 1740 m/sec </font><br /><br />Sounds like a LOI number, or a combination of LOI and lunar orbit capture? <div class="Discussion_UserSignature"> </div>

 

[propforce]

<font color="yellow">They have found problems in building in the SSME air start capability. </font><br /><br />Yes... BIG problem ... could be a "show-stopper".<br /><br />Personally I agree with the change. The SSME was never designed to be a 2nd stage engine and the CLV would have to be built and flown around the limitation of engine. Bring back the J-2S is a much better solution, IMO. <div class="Discussion_UserSignature"> </div>

 

[propforce]

<font color="yellow">Is the tooling or at least the drawings still in existance? Or will they have to start from scratch? </font><br /><br />IIRC, Rocketdyne had built 6 J-2S at the end of Apollo program and delivered to MSFC all wrapped and sealed. They took one out and use the turbomachinery part for the X-33 aerospike engine program. So if my math is correct, there should still have 5 brand new engines sitting in MSFC somewhere.<br /><br />The good news is that much of SSME and RS-68 manufacturing process can be applied to J-2S relatively easily. I don't anticipate the tooling would be a schedule driver. <br /><br />The biggest decision would be to decide if they still want the J-2S carry the separate hydrogen & helium tank as the old J-2 did. <div class="Discussion_UserSignature"> </div>

 

[SpaceKiwi]

I know everything is inter-related at the end of the day, but it's still kind of a nice thought to think that hardware born out of the Saturn/Apollo Program is potentially going to roar back into life in the true successor to Saturn/Apollo. <div class="Discussion_UserSignature"> <p><em><font size="2" color="#ff0000">Who is this superhero?  Henry, the mild-mannered janitor ... could be!</font></em></p><p><em><font size="2">-------------------------------------------------------------------------------------------</font></em></p><p><font size="5">Bring Back The Black!</font></p> </div>

 

[holmec]

>That is what I said 4 months ago and several posters here gave me heck about it. <<br /><br />Shuttle_guy gets no respect! lol <div class="Discussion_UserSignature"> <p> </p><p><font color="#0000ff"><em>"SCE to AUX" - John Aaron, curiosity pays off</em></font></p> </div>

 

[tomnackid]

I don't think NASA has made any decision NOT to use the SME yet. It looks more like they are officially getting around to dealing with the problems of designing an air startable SME and developing a contingency plan if its too difficult. An issue that was known ever since the SME was first proposed as a second stage engine. Personally I would like to see the SME developed into a high performance second stage engine, but I'm not religiously devoted to the idea--whatever works works!

 

[ragnorak]

I thought it was clear from NASA documentation the CEV would use the SSME, RS-25E, and the EDS would use the J-2.

 

[cuddlyrocket]

Spaceref is reporting that the J-2S may be underpowered for the task.<br /><br />Perhaps they're thinking of a bigger SRB to compensate?

 

[propforce]

<font color="yellow">"Sounds like a LOI number, or a combination of LOI and lunar orbit capture?" <br /><br />No the LSAM is to be used for LO!. </font><br /><br />Ooops, you're right. Wrong prop !! <img src="/images/icons/smile.gif" /> <div class="Discussion_UserSignature"> </div>

 

[propforce]

<font color="yellow">"The biggest decision would be to decide if they still want the J-2S carry the separate hydrogen & helium tank as the old J-2 did. " <br /><br />You are referring to the start bottle? </font><br /><br />Yes the start bottle. Technically it also can be used for re-start though I've heard from Saturn guys that, on the J-2, they were not used on 2nd start. <div class="Discussion_UserSignature"> </div>

 

[propforce]

<font color="yellow">I read up on the J2S and it looks like they use solid propellant gas generators for starts. </font><br /><br />SG you're right. They eliminated the GH2 start tank when going from J-2 to J-2S and switched to SPTS instead. They can mount upto 3 SPTS for a 3-start capability on the J-2S. <br /><br />They'll still need a gaseous helium tank, however; ranging from a 700 cu. in. tank for single start to a 4,000 cu. in. tank for a multiple start, which I would imagine could be replaced by the vehicle helium pneumatic system. <div class="Discussion_UserSignature"> </div>