Why not external tank on X-33?

[scottb50]

I was thinking two 60,000 pound engines, quite a bit bigger than Centaur. The idea is similar though, the engines can relit numerous times. Structure would also be more substantial but more rugged and reliable. I was thinking 100,000 pounds of payload. <br /><br />If you use the same Modules that make up the upper stage, as well as the first stage, to build Stations, transfer vehicles, cargo containers, lunar and Mars Stations and whatever else. A standard Module would allow 60x15 feet of unobstructed space, a fuel tank or cargo container. By adding upgrades, power and life-support the same Module could become whatever is needed. <br /><br />It should be easier to store LH2 in orbit because of the lower temperatures, a lot less cryogenic coolers needed. Transfering gasses and fluids in Space has been well proven. In my plans each Module will come with conduits and plug-in connecters Hydrogen, Oxygen, Nitrogen, electricity, data, water, ect., built in. <br /><br />I think it should all be re-usable. The first stage returns for a powered landing at the launch site and the second stage stays in Space for re-use.<br /><br />Anyone know the status of the Shuttle facilities in California, if nothing else the plans still exist. <div class="Discussion_UserSignature"> </div>

 

[propforce]

<font color="yellow">"Transfering gasses and fluids in Space has been well proven. " </font><br /><br />Only when the astronauts pass gases. <div class="Discussion_UserSignature"> </div>

 

[scottb50]

I'm not saying transfer of cryogenics, just gas. No different than what Shuttle has done to run it's fuel cells for 20 some years. <div class="Discussion_UserSignature"> </div>

 

[propforce]

<font color="yellow"> "...It should be easier to store LH2 in orbit because of the lower temperatures, a lot less cryogenic coolers needed..."</font><br /><br />Not at all. Cryogenic liquid hydrogen (LH2) is very difficult to store even in space. To say space is cooler is like saying the Sun is cooler at night, not quite true there. The sun radiation still provides quite a bit of heat to vaporize LH2. The long term space storage of LH2, e.g., space propellant farm, is a subject of much studies for the last 30 years but not much progress. <div class="Discussion_UserSignature"> </div>

 

[scottb50]

Fairly simple thermal insulation works wonders in a vacuum. You would still need cooling, but since you are starting half way, compared to normal temperature conditions, the requirements are reduced. <br /><br />Other than for vehicles gasses would work just fine anyway, so cryogenic requirements would be limited to assuring adequate supply for a specific time. When I said fluids I was thinking water. <div class="Discussion_UserSignature"> </div>

 

[vt_hokie]

<i>Yes, this is my idea. A modern starclipper design!</i><br /><br />That's exactly what I want to see as well! Unfortunately, I think it's unrealistic to expect the private sector to develop such a vehicle, and sadly, it doesn't seem that NASA will do it either. <br /><br />I do hope that the little guys can eventually achieve orbit, but as it stands, that's a long way off. It remains to be seen how well Scaled Composites and Virgin will do with their Mach 3 amusement park ride, and I hope that they pull it off, but orbital systems are obviously enormously more complex and challenging.

 

[scottb50]

http://spaceflight.nasa.gov/shuttle/reference/shutref/orbiter/eps/pwrplants.html<br /><br />From the article:<br /><br />When the reactants enter the fuel cells, they flow through a preheater (where they are warmed from a cryogenic temperature to 40 F or greater); a 6-micron filter; and a two-stage, integrated dual gas regulator module. The first stage of the regulator reduces the pressure of the hydrogen and oxygen to 135 to 150 psia. The second stage reduces the oxygen pressure to a range of 62 to 65 psia and maintains the hydrogen pressure at 4.5 to 6 psia differential below the oxygen pressure. The regulated oxygen lines are connected to the accumulator, which maintains an equalized pressure between the oxygen and the fuel cell coolant. If the oxygen's and hydrogen's pressure decreases, the coolant's pressure is also decreased to prevent a large differential pressure inside the stack that could deform the cell stack structural elements. <div class="Discussion_UserSignature"> </div>

 

[najab]

><i>...warmed from a cryogenic temperature....</i><p>Meaning they were liquid to start with, the system you are describing is part of the fuel cell.</p>

 

[mlorrey]

<blockquote><font class="small">In reply to:</font><hr /><p>What! <br /><br />So you think it’s possible to have a SSTO RLV with wings and that uses a fuel other than Hydrogen. <br /><br />I would like to see that!!!! <br /><br />I was under the understanding the only reason to use hydrogen as a fuel was because you get more power for the weight (despite all the complications of having to have bigger tanks and keeping the fuel at such a low temp) <br /><br />If there a rocket fuel out there that could be handled like kerosene but is more powerful than Hydrogen. <br /><br />Firstly, what is it? <br /><br />Secondly, why aren’t we using it? <p><hr /></p></p></blockquote><br /><br />There are several. LH2 is actually the worst possible fuel to use for an SSTO. Dunn has put a number of papers out there showing why. So has Mitchell Clapp. That doesn't mean its impossible, just that you need to stick with a VTVL with at best partial reusability, as I and Gary Hudson have both shown with concepts involving STS Ext Tanks.<br /><br />The first stage of the Falcon1 rocket is actually an SSTO. With no TPS, it is only recoverable on suborbital trajectories. You could build a second stage for it that would be recoverable, but its payload would be at best half of the current payload.<br /><br />Methyacetylene and cyclopropane are both superior to both LH2 and RP-1 as SSTO fuels, both putting up 2.5 times more cargo in orbit than LH2 for an identical tankage volume.<br /><br />The problem with LH2 is the volume. Sure, it has great BTU/kg, but its BTU/liter suck big donkey balls, all because its density is a measely 0.07 kg/l. This mandates huge fuel tanks that are dreadfully un-aerodynamic. This negates the Isp advantages of LH2 over RP-1. <br /><br />The secret fuel, though, is boron. Pentaborane and diborane were both researched in the 1950's, and have Isp's superior to LH2, while being many times denser. This allows a much smaller vehicle for the same Isp as LH2, thus better overall performance. You can do abou

 

[larper]

[qoute] Boron exhausts as boron oxide, i.e. bauxite<p><hr /><br />Boron oxide is NOT bauxite. Bauxite is the mineral compound from which aluminum is extracted. Boron oxide is simply boron oxide.</p> <div class="Discussion_UserSignature"> <p><strong><font color="#ff0000">Vote </font><font color="#3366ff">Libertarian</font></strong></p> </div>

 

[mlorrey]

I apologize, that is right, I meant to say borax (I always get those two mixed up), which is (Na2B4O7) that results when boron oxide settles into the ocean and reacts with natural sodium. 2 x B2O3 + Na+ + O2 = borax.

 

[scottb50]

Fuel cells use Hydrogen and Oxygen gas. How you store it not a problem. I believe the Shuttle uses heaters at the tank and delivers gas to the fuel cells, while it will be gas it will be pretty cold, hence the heating system at the fuel cell. <br /><br />I'm proposing the same thing, the difference being the gasses would be plumbed throughout the Module, when two Modules dock they will capable of transfering or combining services. I figure the smallest safe Station would be three Modules, the largest could be infinitely large, simply attach more Modules. A Lunar Cycler would have three Modules as a base vehicle with others attached as required. <br /><br />A Module is two or more Segments permanently to each other. A Segment is three rings, the outer rings have Docking Adapters that mate to any other Segment and either identical or altered treatment of the ends. The Central ring uses four reinforced sections, that have smaller versions of the Docking Adapter. Reinforcement connects the End rings to the Central ring with multiple conduits providing structural strength as well as utility. <div class="Discussion_UserSignature"> </div>

 

[tomnackid]

Why won't NASA use boron? Because their budget is controlled by politicians whose reelections are controlled by a bunch of moronic tree hugging weenies that think any smoke is pollution. Boron exhausts as boron oxide, i.e. bauxite, a natural and non-toxic mineral compound. Makes a LOT of beautiful smoke, though.<br />-------------------------------------------------------<br />Please stop filling up threads with reactionary, moronic claptrap. LOX/H2 engines have been considered the "holy rail' of rocketry since the days of Tsiolkovsky--quite a few years before the term "tree hugger" was ever uttered! In fact Von Braun (who never struck me as much of a hippy environmentalist) consideered LOX/H2 rocket engines to be a prime goal for the liquid fuel rocket program. As far as "weenie tree huggers" go most of them don't know LOX from smoked salmon and probably don't care much one way or the other what the space shuttle burns, much less demand from their congressmen that is use hydrogen. (Besides, the whole argument falls apart when you figure in the SRBs that put tons of aluminum and partially burned hydrocarbons into the air with each flight. Why are the "tree huggers" content to let that go?)<br /><br />It was an engineering decision pure and simple. Like any other engineering decision it has its positive and negative points.

 

[space_dreamer]

Thank you for your response, I found it very interesting. <br /><br />I must confess that I don’t have much chemistry knowledge but I will read up on Boron, Pentaborane, diborane, methyacetylene and cyclopropane. <br /><br />What drawbacks are there to these fuels? Are they very expensive, difficult to handle or toxic?<br /><br />

 

[scottb50]

I would think it a lot easier to boil off gas at the tank, with heaters, and transfer the gas then transferring cryogenic liquids and keeping them cryogenic, especially when fuel cells need gasses to operate. <br /><br />What I understand is the temperature of the gasses has to be above freezing to keep water vapor from freezing and causing problems. The gasses combine but the temperature produces ice instead of water and lowers the output.<br /><br />The heaters also maintain the ullage pressure, but that's a separate issue.<br /> <div class="Discussion_UserSignature"> </div>

 

[gunsandrockets]

"Actually, the Shuttle IS the modern Starclipper design--just stripped to the bare bones...The STS is what you get if you take the Starclipper concept and reduce development cost to the bare bones...while trying to cater to DOD needs at the same time. "<br /><br />So the 2,000 tonne Space Shuttle is 'stripped to the bare bones' compared to the 300 tonne Starclipper? 'Stripped' is hardly the phrase that comes to my mind.<br /><br /><br /><br /><br /><br />

 

[gunsandrockets]

"The first stage of the Falcon1 rocket is actually an SSTO. "<br /><br />That's a rather bold claim. So why does SpaceX use a second stage on the Falcon 1 rocket?

 

[mlorrey]

<blockquote><font class="small">In reply to:</font><hr /><p>"The first stage of the Falcon1 rocket is actually an SSTO. " <br /><br />That's a rather bold claim. So why does SpaceX use a second stage on the Falcon 1 rocket? <p><hr /></p></p></blockquote><br /><br />To maximize payload size. The major economic problem with SSTOs is that the amount of payload they can launch tends to be miniscule, due to mass fraction vs Isp issues. The Falcon1 actually has the highest mass fraction of all the launchers out there, about .9, as I recall, which is well within SSTO range for the Isp they are operating at. I believe, though, that they would not be able to launch more than 200-500 lbs into orbit, nor would the launcher be recoverable, as it has no TPS.<br /><br />Making SSTOs is easy, making them reusable is not.

 

[gunsandrockets]

"The secret fuel, though, is boron. Pentaborane and diborane were both researched in the 1950's, and have Isp's superior to LH2, while being many times denser... You can do about as well by adding pure, or nearly pure, boron to RP-1 as a slurry at varying percentages...This still only gets you to about 450 secs of Isp, albiet with a much smaller vehicle size and dry mass."<br /><br /><br />Will you post some links about actual boron fuel performance? I didn't find any information on boron slurries, but I did find this...<br /><br />http://web.chem.ucla.edu/~mfh/<br /><br />"In 1946, following the conclusion of World War II, Project Hermes was organized by the U.S. Army. The purpose was to synthesize boron hydrides in commercial quantities and perhaps use them as fuels in rockets. The heat of combustion of boron hydrides is typically about 30,000 BTUs per pound, while a hydrocarbon fuel, such as JP4 or kerosene, was about 18,000 BTUs. This was a tremendous step up in potential energy content, and it was attractive to people designing rocket engines and weapon systems."<br /><br />"Accordingly, General Electric Company undertook a research and development program in Malta, N.Y., which actually made commercial quantities, several hundred pounds of diborane, pentaborane and decaborane. These more stable boron hydrides are the contributions of Alfred Stock. "<br /><br />"All went well until about 1948, when the plant was cleaned and washed out with carbon tetrachloride, not realizing that carbon tetrachloride and decaborane form an explosive mixture equivalent to nitroglycerin. The plant was blown away. So, live and learn. Anton Burg at USC had warned them that this might happen. They did it nonetheless."<br /><br />"That didn't change things and the rocket program went ahead. In the meantime, a new bomber was designed, the B-70 Valkyrie, an intercontinental bomber capable of reaching the Soviet Union and returning to the Un

 

[mlorrey]

Yes, I'm aware of this. The Merlin engine, though, uses an ablating nozzle, so the boron oxide issue should not interfere with the flow dynamics, since any accumulations on the nozzle surface will ablate off. This is why I thought the engine particularly appropriate for this application.<br /><br />This image:<br /><br />http://www.onera.fr/conferences/ramjet-scramjet-pde/images/slurry-lfrj.gif<br /><br />From this web page on the Onera ramjet missile:<br />http://www.onera.fr/conferences/ramjet-scramjet-pde/<br /><br />Describes boron-kerosene slurry performance in ramjets. Scaling these curves to rocket engine Isp ranges indicates slurry performance in the 400-450 secs range.<br /><br />

 

[tomnackid]

Its not so much a problem of the borate solids fouling the engine as it is the formation of solid particles in the exhaust stream degrades the thermodynamic performance of the engine. When engineers talk about hydrogen being "clean burning" they are not catering to "tree huggers" they are referring to the fact that the only thing that comes out of the exhaust bell is gas at high temperature. So, although boron theoretically has more potential energy in a denser package than hydrogen, hydrogen is much easier to put into PRACTICAL use as a rocket fuel for a variety of reasons.

 

[mlorrey]

This is an issue with the pure boron/borate fuels. With slurries, such as I propose, there is enough hydrogen in the combustion process that the boron oxide really shouldn't precipitate until it it outside the nozzle, unless it is accumulating on the ablative surface. It would accumulate on the surface due to the cooler material of the surface, plus some electrothermal issues dealing with MHD-type stuff, which I have some other thoughts on.

 

[dobbins]

Regardless of when it precipitates it will still be particulate matter and that will cause problems with the EPA. They are in the process of making the standards tougher now, and the enviromental lobby is unhappy that they aren't putting tighter controls on particulate matter.<br /><br />http://www.washingtonpost.com/wp-dyn/content/article/2005/12/20/AR2005122001412.html<br /><br />

 

[propforce]

<font color="yellow"> The Falcon1 actually has the highest mass fraction of all the launchers out there, about .9, as I recall, which is well within SSTO range for the Isp they are operating at. I believe,...... . </font><br /><br />The first stage needs to reach <i>orbit</i> in order to claim SSTO. Stying in orbit after reaching it is even tougher, however. <br /><br /><br /><font color="yellow">Making SSTOs is easy, making them reusable is not. </font><br /><br />True enough. But making SSTO is plenty tough enough. <div class="Discussion_UserSignature"> </div>

 

[mlorrey]

<blockquote><font class="small">In reply to:</font><hr /><p>Regardless of when it precipitates it will still be particulate matter and that will cause problems with the EPA. They are in the process of making the standards tougher now, and the enviromental lobby is unhappy that they aren't putting tighter controls on particulate matter. <p><hr /></p></p></blockquote><br /><br />Ah, the tree huggers come out.<br /><br />Pollution credits are so cheap (NYC paid $250 for credits for all city wide government facility holiday lighting this year), that buying a few for each launch should not be a significant expense.<br /><br />This is a sterling example of the asininity of the LH2 mindset: IF fossil or other pollutive fuels are scarce and must be consumed in a limited fashion, it makes economic sense to use them on economic activities which are very high value (i.e. launching satellites worth millions of dollars), while letting the burger flippers of America commute to work on hydrogen. LH2 in the space program for environmental reasons is absolutely idiotic.