EELVs as manned launch vehicles.

[dwightlooi]

(1) The whole issue about the EELVs not being man rated and the doubts about how and if they can be is BS. The Redstone, the Atlas and the Saturn boosters didn’t exactly have stellar records when it was decided to fly humans atop them. In fact, there had been a string of spectacular failures. They flew manned missions just fine.<br /><br />(2) The EELVs – Delta IV and Atlas V – are really great vehicles for transporting a astronauts into space. The two offers a common payload interface, so theoretically a Crew Transfer Vehicle can be easily designed to be flown on both.<br /><br />(3) If the goal is simply to create a 4-person ride into LEO, the simplest Delta IV or Atlas V with no solids and a single core booster will do just fine. The Gemini Capsule weighed about 2 tons and carries 2 dudes. There is no reason why an 8 ton capsule cannot be developed using today’s composite technology and metallurgy to carry 4 individuals. In fact, even a 4-person maneuverable re-entry vehicle can be made to that weight. Remember, the term CTV implies that it does not have to provide extended habitation and life support in space like a Soyuz or Apollo capsule. 12 hours of air is all that it’ll carry in addition to the astronauts. A separate supply container for the ISS or a separate CEV -- to be rendezvoused with in orbit – will be launched if anything more is needed. The Delta IV and Atlas V will lift 8.1 tons and 12.5 tons to LEO it their simplest zero solid configurations, so there is lift to spare. And, we are not even talking about soon to be available EELVs with the RL-60 upper stage just the good old RL-10 uppers.<br /><br />(4) If the desire is to provide cheap, readily available space transfers, you want as little complexity and components in the system as possible. A Delta IV medium system will have only one RS-68 main engine, and one RL-10B2 upper stage engine and NO solids or a third stage. This alone is enough to lift the CTV to LEO. There is nothing simpler and with less th

 

[najab]

><i>The Redstone, the Atlas and the Saturn boosters didn’t exactly have stellar records when it was decided to fly humans atop them.</i><p>Atlas I'll give you, but Redstone was a proven booster before MR-3 and Saturn didn't fly until late 1961.<p>Anyway, the difference is that Redstone and Atlas were stop-gap "get someone up there before the Russians embarass us some more" booster choices. They were chosen because they were all there was. They knew that there would only be a limited number of flights, and they could afford to kill a few "brave, 100% red white and blue astronaut test-pilot heroes". CEV is going to be the foundation of manned US spaceflight for decades to come. Maybe the EELVs are safe enough, maybe they aren't. But since we're going to be putting all the eggs on one booster, it better be reliable - hence the need to man-rate the system.</p></p>

 

[SpaceKiwi]

""CEV is going to be the foundation of manned US spaceflight for decades to come.""<br /><br /><br /><br />Let's hope only a couple of decades, max, before the subsequent generation of vehicle comes along.<br /><br />Although, in 20-25 years time, hopefully the private sector will have come to the party in a meaningful and significant way. <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>

 

[pathfinder_01]

Man ratting is a little more than just making sure the rocket does not blow up. It is to ensure that vibrations and any other danger in flight will not endanger the crew. Some rockets experience a serious amount of vibration in flight. Vibrations can be tolerable for a satellite since you can take them in account when you are building them, but you can’t do that quite as well with humans. <br /><br />In addition the CEV will need abort modes to give the crew every possible chance of surviving and perhaps even making limited mission objectives in case of a malfunction. Unmanned missions have fewer abort and contingency options built in. Granted space flight is dangerous and there isn’t always a lot that can be done about risk, but when a vehicle is meant to carry humans it should meet stricter standards than something meant to carry a well insured satellite.<br /><br /><br />Also, I don’t know how long the life support systems need to able to support the crew, but 12 hours worth of oxygen seems a bit low. I would expect something able to support the crew for at least 3 or 4 days. It would allow more freedom for timing the launch since the cev can take more time to reach the station and it would allow more freedom on timing the return (i.e. bad weather at sight).<br /><br /><br />Don’t get me wrong I expect that the CEV will be cheaper than the shuttle to operate. I am just not as willing to jump on the CEV is a huge step towards the moon or mars bandwagon. A space capsule is cheap. Building the rest of system is going to be the killer and I really don’t think there is much political will to do so. <br />

 

[dwightlooi]

From a safety stand point the Shuttle is worse than anything else. The STS has solids which cannot be shut off. It has no ability to eject the shuttle during the initial ascent; there is no launch escape booster to shoot the shuttle clear even if a catastrophic failure is imminent. The SSMEs are also some of the most complex and highly stressed engine in service.<br /><br />With the EELVs and an 8 ton capsule, you have the option to do everything with one relatively simple and robust main engine and one simple upper stage motor. Launch escape is easily accomplished with a CTV that has the ability to fire its de-orbit engines and decouple itself from the EELV. A simple solid rocket de-orbit booster is all it takes.

 

[dwightlooi]

Just a little illustration on what I am imagining<br />

 

[najab]

><i>From a safety stand point the Shuttle is worse than anything else.</i><p>Saying that the Shuttle is the worst of two (Shuttle, Soyuz) isn't really saying much. <img src="/images/icons/wink.gif" /><p>><i>A simple solid rocket de-orbit booster is all it takes.</i><p>Ah, but <b>when</b> to fire it, that's the question. A major task in man-rating the EELVs would be incorporating a vehicle health detection system that will give you an early warning that things were going South such that you have enough time to get out of town. Can such a system be incorporated into the EELVs? I think so, but others have their doubts.</p></p></p>

 

[propforce]

<font color="yellow"><i>>>From a safety stand point the Shuttle is worse than anything else.</i></font><br />Saying that the Shuttle is the worst of two (Shuttle, Soyuz) isn't really saying much. <br /><br />Does anyone know the safety record of Shuttle as compared to the Apollo with Saturn ? Since the Saturn launch vehicle was the last thing we had before the STS, and it closest resemblerance to the EELVs, it would interesting to compare the safety record of this two very different launch system.<br /><br /><font color="yellow"><i>>A simple solid rocket de-orbit booster is all it takes.</i></font><br />Ah, but when to fire it, that's the question. <br /><br />Well, you also need a crew escape system and, depending on where in the accent trajectory do you need to abort, the crew capsule maybe the escape module. The worst part would probably be a high Mach/ high q abort. But I don't see this as a major issue at all, if the crew capsule can withstand the reentry load then surely they can be designed into an escape/ejection mode, saffing the crew for a splash down.<br /><br />Keep in mind all these "man rating" is in effect reducing the effective "useful" payload weight to orbit, including the weight of astronauts. One can go crazy with redundancy thinking "more is better". NOT SO !! "More" is a kiss of death in the launch vehicle business. While putting more weight on a woman may not make her more reliable, putting more weight on a launch vehicle may not get it off the ground.<br /> <div class="Discussion_UserSignature"> </div>

 

[propforce]

<font color="yellow"><i>CEV is going to be the foundation of manned US spaceflight for decades to come. Maybe the EELVs are safe enough, maybe they aren't. But since we're going to be putting all the eggs on one booster, it better be reliable - hence the need to man-rate the system. </i></font><br /><br />The EELVs certainly has a far less potential failure modes than the Shuttle System, ranging from the SRB to the ET to the TPS. Even the configuration itself lends to less drag, less aerodynamic shock heating and simply less things that could go wrong. <br /><br />Of course we all know that it only take one thing to go wrong to ruin the day.<br /><br />But the reliability analysis clearly show a trend ---- less parts count = higher reliability.<br /><br />The CEV will clearly do less than what the Shuttle can do today. But you need both a space taxi and a space truck. CEV and its boosters address the space taxi part.<br /> <div class="Discussion_UserSignature"> </div>

 

[propforce]

<font color="yellow"><i>Man ratting is a little more than just making sure the rocket does not blow up. It is to ensure that vibrations and any other danger in flight will not endanger the crew. Some rockets experience a serious amount of vibration in flight. Vibrations can be tolerable for a satellite since you can take them in account when you are building them, but you can’t do that quite as well with humans. </i></font><br /><br />We'll just build a better lazy-boy recliners into the CEV <img src="/images/icons/smile.gif" /><br /><br />Vibration dampers work well for payloads, why not for humans?<br /><br /><font color="yellow"><i>Also, I don’t know how long the life support systems need to able to support the crew, but 12 hours worth of oxygen seems a bit low. </i></font><br /><br />Well, any time duration longer than that we'll have to build a toilet into the CEV! <br /><br />Why do you think it's need 3~4 days? You can either escape into space, or splash down to the ocean, which you'll probably have enough propellant to get you to the Station, if not, then just fire the de-orbit thruster for reentry. <div class="Discussion_UserSignature"> </div>

 

[najab]

><i>Does anyone know the safety record of Shuttle as compared to the Apollo with Saturn ?</i><p>That's an interesting question. There were 10 Saturn 1 launches, 9 Saturn 1-B launches and 13 Saturn V launches. Of course, this includes test launches, some of which didn't include complete vehicles. My quick count says that over the course of the Apollo/Skylab projects there were 18 orbital launches. Of those, none actually failed, but Apollo 6 (IIRC) didn't make it's intended orbit and Apollo 13 sufferered an engine failure in flight.<p>The Shuttle, OTOH, has had 113 launches with one total failure and one in-flight engine shutdown. On paper it would seem that STS compares favourably to Saturn.</p></p>

 

[najab]

><i>Why do you think it's need 3~4 days? You can either escape into space, or splash down to the ocean, which you'll probably have enough propellant to get you to the Station, if not, then just fire the de-orbit thruster for reentry.</i><p>If the CEV is going to be limited to the CTV role, this is true. However I'd like to see it built with the capability of independant flight - never know when they'll be a space telescope that needs repair or something of the like. Even in the crew escape vehicle role a significant loiter time could be useful - if there's a toxic spill on board the crew could retreat to the CEV for a day or so to let the Station's air scrubbers work their magic.</p>

 

[dwightlooi]

<i>That's an interesting question. There were 10 Saturn 1 launches, 9 Saturn 1-B launches and 13 Saturn V launches. Of course, this includes test launches, some of which didn't include complete vehicles. My quick count says that over the course of the Apollo/Skylab projects there were 18 orbital launches. Of those, none actually failed, but Apollo 6 (IIRC) didn't make it's intended orbit and Apollo 13 sufferered an engine failure in flight.<br /><br />The Shuttle, OTOH, has had 113 launches with one total failure and one in-flight engine shutdown. On paper it would seem that STS compares favourably to Saturn. </i><br /><br />Do you mean <b>two</b> total failures -- Challenger and Columbia -- and one inflight engine shutdown?

 

[najab]

><i>Do you mean two total failures -- Challenger and Columbia -- and one inflight engine shutdown?</i><p>No, I meant what I said. There have been 113 <b>launches</b> with one failure and one engine shutdown. <i>Columbia</i> was lost on re-entry, not launch.</p>

 

[tap_sa]

One might argue that Columbia's launch was a failure, the result was just delayed <img src="/images/icons/frown.gif" />

 

[yurkin]

I agree that on the surface the EELV's look like a perfect solution. Except they were never intended to be man rated and I heard there might be considerable difficulties in making them so. <br />I don't know the specifics though.<br />

 

[dwightlooi]

A little illustration as to what I am imagining

 

[dwightlooi]

A little illustration as to what I am imagining

 

[tap_sa]

<font color="yellow">"they were never intended to be man rated and I heard there might be considerable difficulties in making them so. <br />I don't know the specifics though."</font><br /><br />One problem might be acceleration, unmanned vehicles are usually subjected to much higher values because it is more efficient, less gravitational loss.<br /><br />Delta IV Medium looks pretty bening though, calculating from data at astronautix.com the maximum acceleration is about 3.4G , happening just before first stage separation (assuming full payload). After that the ride is very comfy, maximum G reaching only one before second stage burnout.

 

[dwightlooi]

<i>One problem might be acceleration, unmanned vehicles are usually subjected to much higher values because it is more efficient, less gravitational loss.<br /><br />Delta IV Medium looks pretty bening though, calculating from data at astronautix.com the maximum acceleration is about 3.4G , happening just before first stage separation (assuming full payload). After that the ride is very comfy, maximum G reaching only one before second stage burnout.</i><br /><br /><b>Missiles</b> tend to be subjected to very high accelerative loads. The Atlas derived Mercury launch vehicles subjected the astronaut to almost 8Gs of peak acceleration. The EELVs are not missile derived and there is neither the need nor the desired to accelerate satelite launches at that rate.<br /><br />For the most parts, the use of solids tend to result in higher G loadings for the passengers (or payload). Solids have low IpSecs but they are capable of a lot of thrust (albiet for a relatively short duration) for their given size. As a purely liquid fueled booster (and a hydrogen one at that) the Delta IV is not a very hard accelerating rocket.<br /><br />The only problem with the Delta IV (as opposed to say the Atlas V) is that the relatively low maximum thrust of the RS-68 in relation to the launch weight means that the rocket climbs vertically for a longer period during the initial ascent before arching over. But this is more of a danger to the ground facilities than whoever is on the rocket.

 

[propforce]

<font color="yellow"><i>>Do you mean two total failures -- Challenger and Columbia -- and one inflight engine shutdown?</i></font><br />No, I meant what I said. There have been 113 launches with one failure and one engine shutdown. Columbia was lost on re-entry, not launch. <br /><br />Now that's just arguing the techicalities. The root cause of failure was in the launch mode.<br /><br />Bottom line, the Loss-of-Crew (LOC) reliability is what counts.<br /> <div class="Discussion_UserSignature"> </div>

 

[drwayne]

The consensus by the way is that Apollo 13 was probably within seconds of having a total failure of the second stage when the computers shut down the center engine. It was *very* scary out of control.<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]

But the computer *did* shut-down the center engine. The health monitoring sensors did its job. The launch was a success.<br /><br />Otherwise one could argue that the Shuttle is always been one tiles away from disaster. <img src="/images/icons/shocked.gif" /> <div class="Discussion_UserSignature"> </div>

 

[najab]

><i>The root cause of failure was in the launch mode.</i><p>I beg to differ. The <i>damage</i> was done during launch, however the launch was 100% sucessful. The vehicle was inserted into the correct orbit and all on-orbit mission goals were achieved. The question being raised was a comparison of STS to Saturn as a <b>launch system</b>.<p>The root cause of the failure was a high-velocity impact on the wing leading edge, it just happens that the impactor was shed from the launch vechicle itself - it could just as easily have happened on-orbit (MMOD), or by flying into a goose!</p></p>

 

[drwayne]

Not quite. The computer never detected the POGO. The engine was vibrating at 60 G's. It got *very* bad before the engine was shut down. The flow sensors finally detected a flow variation, and that was what shut the engine down - which was a bit of a fluke.<br /><br />If something bad had happened, NASA would have had a PR problem, as a fix had been ID'ed and applied to later vehicles. They didn't want to unstack 13 because, well, the effect had never reached the level at which the pump went into cavitation.<br /><br />Wayne <div class="Discussion_UserSignature"> <p>"1) Give no quarter; 2) Take no prisoners; 3) Sink everything."  Admiral Jackie Fisher</p> </div>