Orion vehicle

[haywood]

Is there some reason why each line is not wrapping the way it should?<br />It makes it very very hard to read some of these posts when you have to keep scrolling left and right, left and right to read them.

 

[Swampcat]

<font color="yellow">"Is there some reason why each line is not wrapping the way it should?"</font><br /><br />It's holmec's long link...which he needs to fix. <div class="Discussion_UserSignature"> <font size="3" color="#ff9900"><p><font size="1" color="#993300"><strong><em>------------------------------------------------------------------- </em></strong></font></p><p><font size="1" color="#993300"><strong><em>"I hold it that a little rebellion now and then is a good thing, and as necessary in the political world as storms in the physical. Unsuccessful rebellions, indeed, generally establish the encroachments on the rights of the people which have produced them. An observation of this truth should render honest republican governors so mild in their punishment of rebellions as not to discourage them too much. It is a medicine necessary for the sound health of government."</em></strong></font></p><p><font size="1" color="#993300"><strong>Thomas Jefferson</strong></font></p></font> </div>

 

[MeteorWayne]

Yes, because holmec's link is so long it is stretching the page out.<br />That's why I asked him to shorten it. <br /><br />Edit:<br />And I asked the goddess of SDC to shorten it, and she did.<br /><br />Thanx, Calli <div class="Discussion_UserSignature"> <p><font color="#000080"><em><font color="#000000">But the Krell forgot one thing John. Monsters. Monsters from the Id.</font></em> </font></p><p><font color="#000080">I really, really, really, really miss the "first unread post" function</font><font color="#000080"> </font></p> </div>

 

[holmec]

Doh! <img src="/images/icons/blush.gif" /> <div class="Discussion_UserSignature"> <p> </p><p><font color="#0000ff"><em>"SCE to AUX" - John Aaron, curiosity pays off</em></font></p> </div>

 

[j05h]

<i>> A "depot" ?</i><br /><br />Yes, a place to hold propellant for use in other applications, be it crewed flights to Mars and the Moon or refueling satellites. <br /><br /><i>> Why would you want a depot? Why not just launch the fuel in tanks as you need them? The reason why I say that is to minimize fuel boiling off and leakage.</i><br /><br />The system outlined above, using Centaur upper stages with updated systems is exactly that. Same goes for a dedicated tank-farm. Both would provide modular, long-term, as-needed storage anywhere between LEO and the Main Belt. <br /><br />Launching on demand is not always possible. If a putative LEO-assembled Mars flight needs say 250t of propellant, it wouldn't necessarily be possible to get all of it there in time, even with HLVs. If propellant can be stockpiled (and they were talking months-to-years with long-duration Centaur), it can be flown up in a manner that drives flight-rates instead of relying on undeveloped rockets. If you want I can dig up some links, but most of it was on Selenian Boondocks. 10 Atlas flights at $250M each totalling 250 tons to orbit is only $2.5 Billion - less than a year's operating costs for Ares V and it can be started today. A commercial venture between Lockheed/ULA and an operator would make more sense than NASA running a tankfarm. There are very few proposed payloads that can not be broken down into less than 25t chunks. Last, a tankfarm can collect even residual propellant from used stages. <br /><br />Modifying existing systems to dock, transfer, settle and stationkeep together makes more sense for a high flight-rate system than dedicated hardware, at least in the next few decades. Using long-duration stages as tankage leaves the propellant where it's meant to be, until needed elsewhere. For a commercial operator, having this kind of tankfarm also allows you to sell/lease the upper stages as needed. <br /><br />Since I'm talking about "reusing the ride" more than payloads, the actual payload <div class="Discussion_UserSignature"> <div align="center"><em>We need a first generation of pioneers.</em><br /></div> </div>

 

[holmec]

Sounds like a step in the right direction.<br /><br />Question:<br />Would it be better to transfer fuel in large tanks and have tanks dock with whatever is using the fuel, or to have a pipe to transfer the fuel? <div class="Discussion_UserSignature"> <p> </p><p><font color="#0000ff"><em>"SCE to AUX" - John Aaron, curiosity pays off</em></font></p> </div>

 

[j05h]

<i>> Sounds like a step in the right direction.</i><br /><br />Yeah. For commercial development especially, stepwise, incremental improvement to existing products makes the most sense. <br /><br /><i>>Question:<br />Would it be better to transfer fuel in large tanks and have tanks dock with whatever is using the fuel, or to have a pipe to transfer the fuel?</i><br /><br />Are you asking if the choice is between swapping tanks and pumping propellant? If so, pumping is less mechanically complex. There is a company supposedly working on a tank-swapping methodology, but dock-and-pump has been reliable for 30 years. The system I'm describing, using Centaur (or other 3rd stage) needs pumping, since part of your fuel stocks comes from residuals left in those stages. It needs to be consolidated. Tank swapping only really works as "tanker" flights where the payload is propellant. Even then pumping is going to be needed eventually. <br /><br />Three methods are immediately apparent for pumping propellant. Ullage motors (probably w/ some pressurization) can be used to settle the tanks. Tanks can be inflatable for mildly cryogenic liquids, then straps can tighten around the tank, "drink bag" style, forcing the liquid out. The third is to centrifuge/spin the tanks when pumping but that has all sorts of balance issues. Other ideas?<br /><br />Josh <div class="Discussion_UserSignature"> <div align="center"><em>We need a first generation of pioneers.</em><br /></div> </div>

 

[holmec]

<blockquote><font class="small">In reply to:</font><hr /><p>but dock-and-pump has been reliable for 30 years<p><hr /></p></p></blockquote><br /><br />Really? In Space? I know the USAF have been in flight refueling since the 50's. But besides the recent Orbital Express mission I'm not aware of any refueling in space being conducted. <div class="Discussion_UserSignature"> <p> </p><p><font color="#0000ff"><em>"SCE to AUX" - John Aaron, curiosity pays off</em></font></p> </div>

 

[docm]

The stories I've read stated that OE was the first in space refueling.. <div class="Discussion_UserSignature"> </div>

 

[j05h]

<i>> Really? In Space? I know the USAF have been in flight refueling since the 50's. But besides the recent Orbital Express mission I'm not aware of any refueling in space being conducted.</i><br /><br />The technology used in Progress is available if needed - that is the "30 years" I referred to. The Russian space program has been transferring propellant for a long time. Orbital Express brings docking and fuel transfer up-to-date and puts it in an American context.<br /><br />J <div class="Discussion_UserSignature"> <div align="center"><em>We need a first generation of pioneers.</em><br /></div> </div>

 

[holmec]

Thanks for the info. <div class="Discussion_UserSignature"> <p> </p><p><font color="#0000ff"><em>"SCE to AUX" - John Aaron, curiosity pays off</em></font></p> </div>

 

[j05h]

Yer welcome. The next issue for propellant transfer, and one that does make reconsidering tank-swapping instead of pumps, is the how of cryogenic transfer. Even Methane/LoX will be challenging. Both Progress and OE were transferring caustic hypergolics instead of cryofuels.<br /><br />These are the tank-swap guys:<br />http://www.lunartransportationsystems.com/default.aspx<br /><br />josh <div class="Discussion_UserSignature"> <div align="center"><em>We need a first generation of pioneers.</em><br /></div> </div>

 

[jimfromnsf]

Just pressure differential under low g acceleration. The connections will be the challenge