CEV, going backwards one step at a time...

[spacefire]

http://www.space.com/news/060120_cev_overhaul.html<br /><br />what about the touted parts commonality with the current STS, by using SSMEs for the 2nd stage?<br /><br /><br />what about the argument...well it's a capsule but it's gonna be a BIG capsule? <br /><br /><br />personally, I couldn't care less about whether it uses a more powerful SSME 2nd stage or a hundred segment booster, but obviously this program is going to be different in a bad way from what NASA lovers joyously swallowed last year.<br /> <div class="Discussion_UserSignature"> <p>http://asteroid-invasion.blogspot.com</p><p>http://www.solvengineer.com/asteroid-invasion.html </p><p> </p> </div>

 

[trailrider]

The problem is you just can't plug an SSME, ground ignited into a 2nd stage configuration as-is! While everyone touted that in the original concept, it was always with the idea of, "Well, we'll make a simpler version that will cost less to build." <br /><br />"All" they had to do was change the turbopump design, enlarge the bell for more efficient use at higher altitude, add an igniter, use a different style construction, etc. But that amounts to changing out every part except the manufacturer's name plate. And then you have to change the plate! And then you have to do a LOT of testing to man-rate the "old, but improved SSME"! Apparently there are J-2 drawings and even tooling left over from Saturn V. Still have to re-certify the new units, but you are starting from a design that was INTENDED to be at-altitude ignited in the first place. Lower thrust, and larger propellant tanks (I think), so the weight goes up and you need a higher-thrust 1st stage. That's where the 5-segment SRM comes in. I'm NOT enthusiastic about ANY SRB/SRM/firecracker, but ATK-Thiokol has already static tested one, and apart from a decision on whether to recover the 1st stage (would require a larger parachute subsystem), and installing the retros on the aft skirt, plus some sort of roll control, it should be ready to go.<br /><br />No, I don't like the idea of the smaller diameter command module. But I like the idea of NO manned vehicle after the orbiters are grounded A LOT LESS! In other words, I'll take what I can get, and hope for more later!<br /><br />What's REALLY a pain is that I now have to modify my 1/144 scale model of the "Stick" that I use in my talks to "future" engineers, scientists, astronauts (K-12th grade kids)! <img src="/images/icons/frown.gif" /><br /><br />Ad Luna! Ad Aries! Ad Astra!

 

[spacefire]

I thought there was NO tooling and drawings left from the old Saturn rockets. If you are right about that, I guess it would make sense to use them, but it's still a step backwards!!! <div class="Discussion_UserSignature"> <p>http://asteroid-invasion.blogspot.com</p><p>http://www.solvengineer.com/asteroid-invasion.html </p><p> </p> </div>

 

[tomnackid]

If they stuck with the SME you would complain that it would be too expensive and would take to long to develop when there is a perfectly good J-2 second stage engine just waiting to be used. Just admit it, you will criticize anything to do with CEV no matter what.

 

[tap_sa]

<font color="yellow">""All" they had to do was change the turbopump design, enlarge the bell for more efficient use at higher altitude, add an igniter"</font><br /><br />I get the bell redesign but why need to change turbopumps? And doesn't the SSME already have built-in spark igniters?

 

[henryhallam]

This is about a 33% reduction in volume.. a pity. But as long as it flies, I will be happy.

 

[spacefire]

I wonder how the reduction in volume is going to affect the number of seats.<br />Maybe...only 3 astronauts will be able to use the CEV to go to the Moon. <div class="Discussion_UserSignature"> <p>http://asteroid-invasion.blogspot.com</p><p>http://www.solvengineer.com/asteroid-invasion.html </p><p> </p> </div>

 

[spacefire]

I was against the CEV , which I consider a retrograde step in manned space exploraqtion from the very beginning. I was sure it will not leave up to the promise of delivering a moon base and a manned mission to Mars.<br />the recent developments reinforce my point. <div class="Discussion_UserSignature"> <p>http://asteroid-invasion.blogspot.com</p><p>http://www.solvengineer.com/asteroid-invasion.html </p><p> </p> </div>

 

[josh_simonson]

The CEV is just a taxi from the ground to LEO and back again. In the grand scheme of things for lunar and especially mars exploration it's role is relatively limited. <br /><br />The size and weight of the CEV will have a far more significant impact on it's utility in regards to the ISS. Since the old design could carry 8 in a pinch, the new design should still be able to carry 6 if needed.

 

[tomnackid]

"I wonder how the reduction in volume is going to affect the number of seats. <br />Maybe...only 3 astronauts will be able to use the CEV to go to the Moon."<br />-------------------------------------------------------------------------------------<br />That still beats the 0 astronauts going to the moon in the shuttle!<br /><br />Besides, 5 meters is still much bigger than Apollo (3.9 meters).

 

[tplank]

A dumb question of the non-rocket scientists here: why the need for the weight savings? Is that strictly a result of the engine changes or are there other factors. <div class="Discussion_UserSignature"> <p>The Disenfranchised Curmudgeon</p><p>http://tonyplank.blogspot.com/ </p> </div>

 

[darkenfast]

Other than fact that it seems to cheer you no end to gleefully point out problems with the development of the CEV (of which there will be many, as there would be with any complex new system), I see no real facts to back up your assertion regarding the contribution that this vehicle will make towards new expeditions to the moon and eventually, to Mars. <br /> <br />1. The J-2S will be required for the upper stage of the CaLV, now it's going to be common to both vehicles. <br />2. The SSME is going to be used anyway on the core stage of the CaLV, this eliminates the requirement for re-engineering the vehicle for an air start. Only one version will now be needed.<br />3. The Five-Segment SRB has already been tested, and it will now be common to both launchers (with slight differences in the control systems).<br />4. If you read the ESAS study, much of the work was done assuming a five meter diameter CEV. The 5.5 seems to have been a fairly late change. They just went back to the other version.<br />5. I believe the tankage for the five-meter CEV will now be about the same diameter as the Delta IV. Does anyone here know if this is true and how it might effect the cost?<br />6. If it is established that Methane is needed, it can be added later. This takes some pressure off the early years. <br /><br />These things add up to a rationalization of the system that will make not only the CEV fly sooner, but the CaLV as well. The whole point is to get us back into deep space with the money that is realistically available, not to propose pie-in-the-sky dreams that don't have a chance of getting funding in the near future.<br />Show me any other manned spacflight system that hasn't had changes made as it progressed from concept to hard drawings. This is the most coherant system to come along in decades. If it isn't "sexy" enough for the space cadet-crowd, tough. Unless the enemies of the space program are succesful, it will work.

 

[darkenfast]

Further to the above: Dr. Doug Stanley of Georgia Tech, who headed the team that published the ESAS report, has been on nasaspaceflight.com again today, discussing this story and some of the background for the 5 vs. 5.5m and the choice of options for the CLV. Although he is not involved right now, this is pretty close to the horses mouth when it comes to understanding how the ESAS team came to the conclusions that they did. He does reply to questions.

 

[SpaceKiwi]

A great summary of the rationale behind the changes, darkenfast, thanks. I came into this thread thinking "uh-oh, Shuttle compromises" but it does seem the 'eye' is still squarely on the same 'ball'. <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>

 

[nolirogari]

Shuttle_guy, you are my hero! I keep reading all of this stuff posted by these nay-says who are spring loaded to the negative position and thinking how thankful I am that these forums were not around in the early 1960s when Apollo was developing. "What! The LEM is gonna have just 4 legs? NASA promised us 5 legs! Here we go again!" "What! There is only going to be one docking hatch on the LEM? There goes the moon to the Soviets!" I wonder how far Apollo would have gotten under this type of myopic and under informed attack. Of course no one in the early 60s said "What! A US President will be elected who will want to put an end to the entire program!" <br /><br />And the way that the myth of the "missing" Apollo drawings keeps growing... sheeesh. Folks here's what everyone should really be concerned about... The Gap. And I don't mean the store at your local mall. The less the gap- the less the chance for the anti-space vote grubs to worm in.<br /><br />Thanks for stepping in with informed common sense Shuttle_guy (and others)

 

[frodo1008]

Agreed totally! I have NEVER read anything from the various negativists on these boards that would actually be helpful to NASA in a practical sense! <br /><br />Some of the most knowlegeable positive people on these boards have frankly been driven from space. com by this type of attitude, so we do owe a debt of gratitude to people like shuttle_guy who have persisted and stay here anyway!<br /><br />No system (and I have actually worked on such engines for some 37.5 years before retiring from Rocketdyne in the year 2000) is EVER what it started out to be! Changes are a constant factor because we are constantly learning, but NASA and its main contractors have done a truly magificent job in even keeping the dreams of true space enthusiasts alive at all over these many years!<br /><br />If they can't make the CEV plans work then NOBODY else is either! It is this practical and affordable program that will either bring back the true spirit of exploration, or people such as spacefire can just sit on their posteriors for the next 30 years (and even people such as Burt Rutan know that the pure private efforts are not even going to reach LEO before 2020, let alone go all the way to the moon)! <br /><br />So spacefire, spend your time just knocking this effort, but most of the rest of us would like to see the US go back to the moon both for further exploration, and even to make permanent bases there. We would also like to see human beings on Mars by 2030. That is for me at least if I live to be some 88 years old! <br /><br />But I really don't worry too much about that as I actually was a part of the earliest efforts, and got a pleasure out of contributing to such as Apollo!! It WAS indeed a great time in the history of man, and I do hope that NASA can at least bring back some of the same feeling for the young people of today!

 

[najab]

><i>...enlarge the bell for more efficient use at higher altitude...</i><p>I thought the SSME was already optimised for high-altitude?</p>

 

[shoogerbrugge]

<blockquote><font class="small">In reply to:</font><hr /><p>3. The Five-Segment SRB has already been tested, and it will now be common to both launchers (with slight differences in the control systems). <p><hr /></p></p></blockquote><br /><br />First I'd like to thank everybody for getting the picture clear for us non-engineers, great reading!<br /><br />Second, weren't there problems with recovering a 5 segment SRB? Or is it no longer within the plan to re-use them?<br /><br /><br />

 

[najab]

It's only just cheaper to reuse the current SRB, the 5 segment will be coming down from higher and faster and will land further downrange - making recovery that little bit more expensive. It might not be worth the cost to recover them - unless the CEV flight rate is higher than currently predicted.

 

[mattblack]

I said in a much earlier post that they should use 2x J2s for the CLV upperstage, even if there is a slight performance penalty. The numbers are an interesting comparison:<br /><br />SSME -- Weight; 7500 pounds, 453 seconds isp (vacuum), thrust (vacuum) 512,000lbs.<br /><br />J-2S -- Weight; 3087 pounds, 436 seconds isp (vacuum), thrust (vacuum) 256,000 pounds.<br /><br />It's a reasonably close call, perfomance wise: 2x J-2S is lighter than 1x SSME, but the isp efficiency is less, even if the thrust is the same. With some or most of the shortfall taken up by a 5x segment SRM (to be used on the CALV heavy anyway), you'd have a commonality of design in the booster and engines of both vehicles. The SSME will no longer need an expensive, or time consuming development program to make them air-startable, so there is a more "off the shelf" element to their use. And since they'll be expendable I say throttle the suckers up to 109, 112% percent of more!!<br /><br />Also, there was a concern that for OSHA reasons, the recovery divers for the 5-segment SRMs would have to go deeper, risking the bends. Well, it's time for new diving gear and/or procedures, folks.<br /><br />Also, the CEV may now be going down from 5.5 meters diameter to 5 meters. Well, I always thought 5.5 meters was a shade on the 'extravagant' side, including weight wise. 5 meters aint so bad.... Er, as long as they don't shrink the thing even more; then it'll get a tad tight for 4 people, let alone 6.<br /><br />I'm still concerned by the loss of LOX/Methane though. That's disappointing. I'd go for LOX/Ethanol (330 seconds isp). Still, if they now want to use hypergolics; would using 2x Shuttle OMS-derived engines in the CEV Service Module give the desired delta-v?<br /><br />http://www.astronautix.com/engines/ome.htm<br /><br />They certainly are "man-rated!" <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>

 

[spacefire]

air startable SSMEs, with their greater thrust and being man-rated, might someday be used again for a reusable spaceplane, maybe a TSTO with no SRBs.<br />obviously NASA does not envisage that kind of usage for the shuttle components, and yet they have not started to develop completely new man-rated engines. <div class="Discussion_UserSignature"> <p>http://asteroid-invasion.blogspot.com</p><p>http://www.solvengineer.com/asteroid-invasion.html </p><p> </p> </div>

 

[najab]

It could, who knows?

 

[henryhallam]

Does the SM really need the thrust provided by two OMS engines? After all SM + CEV should end up being quite a bit lighter than the Orbiter. I can see the advantages in redundancy though.

 

[najab]

Right, I knew it wasn't optimised for sea-level but I thought it was designed for higher than 60,000ft. I had something like 100,000 in mind.

 

[SpaceKiwi]

<blockquote><font class="small">In reply to:</font><hr /><p>I said in a much earlier post that they should use 2x J2s for the CLV upperstage, even if there is a slight performance penalty. The numbers are an interesting comparison: <br /><br />SSME -- Weight; 7500 pounds, 453 seconds isp (vacuum), thrust (vacuum) 512,000lbs. <br /><br />J-2S -- Weight; 3087 pounds, 436 seconds isp (vacuum), thrust (vacuum) 256,000 pounds.<p><hr /></p></p></blockquote><br /> Hi matt, sorry for such a basic question, but just so I am really clear on this ... the ISP figure refers to the engine efficiency in that, the higher the figure, the less propellant is needed or used to generate '<i>x</i>' amount of thrust? <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>