ESA, the CEV and the Soyuz

[gunsandrockets]

"One of the reasons the Russians are dropping the Soyuz is the complexities an orbital module adds to the the LES."<br /><br />If you have any new source to back that up I'd sure like to see the link.

 

[gunsandrockets]

"A six person Soyuz with the capabilities of the CEV would weight about the same as the CEV. "<br /><br />What is your reasoning to support that? The 3 man Soyuz provides more space and less mass than the 3 man Apollo. Why wouldn't a Soyuz 2.0 supply more space and less mass than an Apollo 2.0?<br />

 

[gunsandrockets]

"The LES is attached to the shroud which has to lift the OM and the RM away from the rocket, then jettison, then the shroud has to release, then the OM has to be jettisoned so the chutes on the RM can be used. Far more complex than the Apollo LES lifting the CM and it's protective cover, then releasing the CM from it's cover."<br /><br />There is no reason the Soyuz launch escape sequence must follow the process you just described. Since the descent module is at the base of the launch escape shroud, there is no reason why the descent module could not separate by itself away. It would not surprise me it all if that is already the method the current Soyuz sytem works by. In other words, no more complex a launch escape system for the Soyuz than for the Apollo. <br />

 

[JonClarke]

"Getting rid of a loaded Orbital Module greatly improves the task of a Soyuz crew escaping a launch abort scenario too."<br /><br />Obviously the Russiand disagree. And since their abort systems are worked on both occasions they have been called to I suggest their judgement is to be respected.<br /><br />Jon <div class="Discussion_UserSignature"> <p><em>Whether we become a multi-planet species with unlimited horizons, or are forever confined to Earth will be decided in the twenty-first century amid the vast plains, rugged canyons and lofty mountains of Mars</em>  Arthur Clarke</p> </div>

 

[JonClarke]

"And I just can't think of any modern day missions where an Orbital Module would 'make sense'...."<br /><br />Easy. Free flying missions requiring a research payload. Mixed crew-cargo missions to stations. A great many spacecraft design have used a disposable orbital module for these missions, not just Soyuz. Shenzhou, Kliper, Big Gemini, MOL, TKS. It is clearly not and outdated approach and we will see it for decades to come.<br /><br />Jon <div class="Discussion_UserSignature"> <p><em>Whether we become a multi-planet species with unlimited horizons, or are forever confined to Earth will be decided in the twenty-first century amid the vast plains, rugged canyons and lofty mountains of Mars</em>  Arthur Clarke</p> </div>

 

[lampblack]

<font color="yellow">No, the 4 other guys would do very well in their launch and landing suits and stay in their seats.</font><br /><br />Thankee... I shoulda thought of that. <img src="/images/icons/wink.gif" /><br /> <div class="Discussion_UserSignature"> <font color="#0000ff"><strong>Just tell the truth and let the chips fall...</strong></font> </div>

 

[mlorrey]

The CEV's lunar delta v requirements are not going to be met by its mission module propulsion, any more than Soyuz's translunar trajectory is by its own mission module. Both will require a lunar transtage, and, what do you know, the Russians have a well developed and proven transtage, the Block D, in production and with a proven record. <br /><br />What is more, the Soyuz LES is an in-production and proven system that has worked on every occasion it has been used. Given the economic comparative advantages of Russian manufacturing, using the Soyuz LES is the smarter and more economical option.

 

[mlorrey]

Firstly, you are very wrong here. The Soyuz was specifically developed for lunar missions, which you would know if you'd studied its development at all. Its heat shield is built to reenter at 25,000 mph in a skip maneuver, and one version of the Soyuz was specifically built with lunar insertion capability.

 

[najab]

><i>Firstly, you are very wrong here. The Soyuz was specifically developed for lunar missions, which you would know if you'd studied its development at all.</i><p>If you had studied it's development as well, you would know that (a) the Soyuz wasn't developed <b>specifically</b> for Lunar missions; and (b) that when used for Lunar missions the bulk of the dV would have been provided by another module.</p>

 

[gunsandrockets]

What is your reasoning to support that a Soyuz 2.0 would be as heavy as an Apollo 2.0? <br /><br />"Engineering judgement. For one thing the Soyuz has a very limited performance, around 700 ft/sec delta V while the CEV mission requires about 6,000 ft./sec delta V." <br /><br />"You can not look at a LEO vehicle with very limited capability and use that data to scale it up to a vehicle for a different mission !"<br /><br />I will describe how you are wrong. The Apollo CM was designed for three people and for surviving lunar returns, so are some versions of the Soyuz. (And yes I am well aware that the Soviets planned only a two man mission during the moon race, but that has nothing to do with the living volume/mass restrictions of the Soyuz crew compartments and everything to do with the more limited mass the Soviets could launch towards the moon compared to the Saturn V. Current plans for cislunar Soyuz tourism flights employ the three man Soyuz.) The Soviet design choice of splitting the living areas of the Soyuz into a separate obital module and descent module was superior to the Apollo design choice of using a single manned module. Not only did the Soyuz provide it's crew with more total living volume than the Apollo CM, the Soyuz two-module combination was lighter than the Apollo CM.<br /><br />And since the manned component of the Soyuz is lighter than the Apollo's, that mass advantage mutiplies all the way down the line. A Soyuz launch escape system would be lighter than an Apollo launch escape system, since the Apollo capsule is heavier. A Soyuz service module could be lighter than an Apollo service module that provides the same delta vee since the Apollo is heavier. A launch vehicle could be lighter for Soyuz since the Apollo is heavier. And an earth departure stage could be lighter for Soyuz since the Apollo is heavier.

 

[gunsandrockets]

"You need to do a little research, based on the above statement you do not understand the Soyuz vehicle."<br /><br />"The Orbital module is above the descent module thus they both must be aborted with the LES."<br /><br />Of course I know that. Let me try and make my point once again.<br /><br />Dobbins described an abort procedure where after the LES/shroud pulled the orbital-module+descent-module away from the launch vehicle, the Soyuz LES/shroud would separate from BOTH the orbital module and descent module while both modules are still connected to each other. Then the orbital module would have to be jettisoned before the descent module could deploy it's parachute.<br /><br />I merely pointed out that since the descent module would be at the bottom of the LES/shroud modules combination (with the orbital module above the descent module), it would be a simple matter for a single jettison event to separate the descent module away from everything else. The descent module could just fall out the bottom while the orbital module remains connected to the LES/shroud.<br /><br />The point being that the LES proceedure need not be more complex for the Soyuz than for the Apollo.<br /><br />

 

[gunsandrockets]

Anything more to add?

 

[avmich]

I'd like to note that the mass of the spacecraft is seriously influenced by its delta V requirements. Consider Soyuz and Apollo. Soyuz has a returning capsule of about 3 tons and orbital module of about 1,2 tons, total 4,2 tons. The rest is service module (sorry, terms aren't exact), about 3 tons, of which about 900 kg is fuel. For Apollo, the Command Module was 5,8 tons - only 1,6 tons heavier than Soyuz, or about 35%. The Service module for Apollo was 24,5 tons - about 8 times bigger, than Soyuz' - no wonder, since it had much bigger delta V.<br /><br />The version of Soyuz, which was intended to fly to the Moon, also was somewhat heavier - and was going to be lifted by N1.<br /><br />My point is that, though Soyuz is lighter than Apollo - and the separable orbital module does play a role in it - the masses don't differ that much - not several times, at least. We can consider that Apollo's TPS was somewhat overdone, and Soyuz' will weight some more when having TPS for return from the Moon, the difference will be even less, though will still exist.

 

[gunsandrockets]

Keep in mind that the Apollo capsule was heavier than the Soyuz even though the Apollo capsule had less living space. Should a Soyuz two module design be sized the same as an Apollo single module design the mass difference favoring the Soyuz would be even greater.