ARES FLEX -- Super Heavy Lift System

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dwightlooi

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<p><strong>The biggest disadvantage of a LH2/LOX rocket is the fact that the density of liquid hydrogen is horrible.</strong> Combined with an approximately 5:1 mixture ratio (volumetric), it means that hydrogen stages have to be physically very large for the mass of propellant they carry. If you look at a typical Hydrogen fueled rocket stage, about 4/5ths of its length is typically hydrogen tankage with roughly 1/5th being the oxygen bunkerage. In fact it would have been closer to 4/5th to 1/6th were it not for the domes at each end of the tanks. This huge enveloped volume requirement for LH2 means structural weight and in turn reduced propellant mass fraction. To add to the problem, the highly cryogenic Hydrogen requires a rather thick layer of insulation which itself is not weight free. </p><p>Hence, <strong>won't it be nice if we can dump some of that structure along the way?</strong> The Atlas dumped a pair of engines from its balloon tanks to take the Mercury capsule to orbit. In the following proposal, we dump not just the engines no longer required in the later stages of the ascent, but also the empty hydrogen tanks.</p><p>This concept evolves around using the curently proposed 10m ARES Core Stage. But, instead of having six RS-68B engines on the core stage we surround it with six Delta IV CBC derived Hydrogen Strap-Ons -- each with its own RS-68 engine and all the hydrogen fuel that engine will burn. These Strap-Ons carry no oxygen and are roughly 30% longer than the Delta IV CBC, giving them a capacity of about 80 tons of LH2. The Core stage carries all the oxygen needed by the strap-ons. In addition, it also carries a seventh RS-68 engine with about 200 tons of LH2 and 600 tons of LOX for it.</p><p>At launch, two 5-segment SRBs helps this monster with seven RS-68 engines off the pad. After the booster burn out, the hydrogen engines continue to propel the vehicle with a total of up to 2100 tons of thrust, throttle back as needed as the vehicle lightens. The Core engine however never throttles back. Once the hydrogen in them are used up, the Strap-Ons fall away removing the mass of the hydrogen tankage and the heavy RS-68 engines with them. The now significantly lightened Core stage continues the ascent with a single RS-68 on full power pushing the now significantly lightened vehicle with greater efficiency than if we are to carry empty hydrogen tanks and a half dozen engines whose full thrust is no longer needed. The core stage will burn out after a burn that is about twice as long as the strap-ons. The Earth Depature stage then kicks in for final orbital insertion.</p><p>By crude calculations, the increased fuel load and greater overall propellant mass efficiency should endow such a vehicle with a 250 ton lift capability. For missions requiring less payload capacity, we can use only four or even two strap-ons instead of six and partially tank the core stage. Because of the huge discrepancies between hydrogen and oxygen volumes used in a LH2/LOX rocket, the resultant inefficiency in partially tanking a core stage designed to store dense LOX is not particularly significant, because most of the unrequired volume and mass would ahve been removed by the removal of the Strap-Ons.</p><p><br /> <img src="http://sitelife.space.com/ver1.0/Content/images/store/5/5/35537f02-0606-4463-a5ef-18fb7462cbcd.Medium.jpg" alt="" /><br />&nbsp;</p><p>http://img177.imageshack.us/img177/8421/aresflexzy8.jpg&nbsp;</p>
 
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nimbus

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For splitting hairs, but that should be spelled VII, not IIV. <div class="Discussion_UserSignature"> </div>
 
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dwightlooi

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<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>For splitting hairs, but that should be spelled VII, not IIV. <br /> Posted by nimbus</DIV></p><p>Yes, you are right. I goofed.&nbsp;</p>
 
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shuttle_guy

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<p>Your concept of dropping as much dead weight as possible as soon as possible&nbsp;is good. This, of course, is&nbsp;&nbsp;idea behind staging. </p><p>However having 7 LH2 tanks reduces the savings that you gain by having the strap ons&nbsp;since the overall tank structure is heavier than one big LH2 tank.</p><p>Plus you add the weight associated with the hardware to hold the strap on tanks in place and subsequently jetteson the tanks. In addition you add the structure of the 6 nose fairings and the electroncs and explosives needed to jetteson the 6 stap ons.</p><p>As with any concept, the viability of this concept would be proven by a very extensive and deailed analysis.</p> <div class="Discussion_UserSignature"> </div>
 
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spacelifejunkie

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<p>Practically speaking, the increased complexity and money spent testing this bad boy might make it theoretically better but economically suicidal.&nbsp; I'm worried the changes currently being made (minor compared to these) are already too much.&nbsp; I worry about the future of manned spaceflight.</p><p>SLJ<br /></p>
 
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