Research into rocket designs that could double performance!

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space_dreamer

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From Spacedaily-<br /><br />When you think of future rocket technology, you probably think of ion propulsion, antimatter engines and other exotic concepts.<br />Not so fast! The final chapter in traditional liquid-fueled rockets has yet to be written. Research is underway into a new generation of liquid-fueled rocket designs that could double performance over today's designs while also improving reliability.<br /><br />Liquid-fueled rockets have been around for a long time: The first liquid-powered launch was performed in 1926 by Robert H. Goddard. That simple rocket produced roughly 20 pounds of thrust, enough to carry it about 40 feet into the air. Since then, designs have become sophisticated and powerful. The space shuttle's three liquid-fueled onboard engines, for instance, can exert more than 1.5 million pounds of combined thrust en route to Earth orbit.<br /><br />You might assume that, by now, every conceivable refinement in liquid-fueled rocket designs must have been made. You'd be wrong. It turns out there's room for improvement.<br /><br />Led by the US Air Force, a group consisting of NASA, the Department of Defense, and several industry partners are working on better engine designs. Their program is called Integrated High Payoff Rocket Propulsion Technologies, and they are looking at many possible improvements. One of the most promising so far is a new scheme for fuel flow:<br /><br />The basic idea behind a liquid-fueled rocket is rather simple. A fuel and an oxidizer, both in liquid form, are fed into a combustion chamber and ignited. For example, the shuttle uses liquid hydrogen as its fuel and liquid oxygen as the oxidizer. The hot gases produced by the combustion escape rapidly through the cone-shaped nozzle, thus producing thrust.<br /><br />The details, of course, are much more complicated. For one, both the liquid fuel and the oxidizer must be fed into the chamber very rapidly and under great pressure. The shuttle's main engines would drain a swimming pool f
 
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vogon13

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An obvious improvement to the SSME engine, throttling the fuel in addition to the oxidiser was not persued, the 'run rich' philosophy protects the engine components from chemical attack from the oxygen. Also, the mechanical complexity would be large, and the payoff in payload is rather small, as the LH2 is the lightest liquid fuel possible.<br /><br />Other fuel chemistries, of course, would not be so advantageous in that regard.<br /><br /> <div class="Discussion_UserSignature"> <p><font color="#ff0000"><strong>TPTB went to Dallas and all I got was Plucked !!</strong></font></p><p><font color="#339966"><strong>So many people, so few recipes !!</strong></font></p><p><font color="#0000ff"><strong>Let's clean up this stinkhole !!</strong></font> </p> </div>
 
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dobbins

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There are problems with LH2 that offset many of it's advantages. It's low density requires larger heavier tanks and larger heavier pipes to move the fuel. It's very low temperatures requires even more insulation than LOX and this again adds weight and cost to the launch vehicle. There is also the matter of the high cost of LH2. Kerosene and LNG are both cheaper than LH2 meaning lower fuel costs and smaller cheaper tanks. Kerosene doesn't require any insulation which means lower handling costs and lighter cheaper fuel tanks. LNG doesn't even require as low a temperature as LOX which means less insulation is needed for fuel tanks and lower handling costs.<br /><br />The best choice for a fuel is the one that can put a kilogram into orbit for the lowest total cost, if you can shave a few dollars per kg off launch costs by using a different fuel than LH2 then that is the best choice.<br /><br />A Ferrari has better performance than a Chevrolet, but few people can afford the high costs of buying and maintaining a Ferrari. We need a "space Chevy" instead of just looking at raw performance.<br /><br />
 
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cuddlyrocket

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"Such a design has never been used in a liquid-fueled rocket in the U.S. before...."<br /><br />Has it been used somewhere else? If so, it's not new, is it?<br /><br />Could still be detailed improvements though.
 
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rsp1202

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The Russian RD-180 aboard the Atlas V runs oxygen rich and is of very high performance, not of extreme complexity, and not reusable. U.S.-designed rocket motors, especially the SSME, take a different tack. The RS-68 is different still. Missions differ, but why such a large divergence in theory and practice?
 
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larper

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Ok, I must be missing something...<br /><br /><blockquote><font class="small">In reply to:</font><hr /><p>One of many innovations being tested by the Air Force and NASA is to send all of the fuel and oxidizer through their respective preburners. Only a small amount is consumed there--just enough to run the turbos; the rest flows through to the combustion chamber. <br /><br />This "full-flow staged cycle" design has an important advantage: with more mass passing through the turbine that drives the turbopump, the turbopump is driven harder, thus reaching higher pressures. Higher pressures equal greater performance from the rocket. <p><hr /></p></p></blockquote><br />How can passing all of the fuel/Ox through the turbines work? If all of the liquid is passing through the turbines, what are the pumps pumping? Wouldn't this be like Hoover dam using the electricity it generates to refill Lake Mead? <div class="Discussion_UserSignature"> <p><strong><font color="#ff0000">Vote </font><font color="#3366ff">Libertarian</font></strong></p> </div>
 
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rocketman5000

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From what I understood is that the fuel would pass through the pumps to the preburner to increase temperature then expanded through the turbine to run the pumps. <br /><br />Same as the process today except all the fuel would go through the preburner
 
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mikejz

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I’m very suspicious of the term ‘double performance’ without an explanation of what they are talking about.
 
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space_dreamer

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It good to see that, rocket engine research is still going on in the US, I thought it stopped with the demise of the RS-84 and the SLI.
 
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tap_sa

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<font color="yellow">"I’m very suspicious of the term ‘double performance’ "</font><br /><br />Same here. This has little or zero impact to Isp because that's depends more on the fuel itself, area ratios and such. T/W improves some but doubling it is seriously doubtfull. About the only thing that might have double performance are the turbines.
 
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space_dreamer

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"The only thing that might have double performance are the turbines" - That would make more sense.
 
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larper

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But, my point is, is that the fluid going through the turbine performs work. Thus, it must lose energy by being slowed down. The pumps are trying to speed the fluid up. So, by slowing the fluid down, you are really speeding it up?????<br /><br />It would seem to me that the PERFECT solution is that the fluid passes from the tanks to the combustion chamber at the highest rate under the highest pressure. That mean "get everything out of the fluid's way", right? So the PERFECT turbo pumps pump the fluid using as little of the actual fluid itself to power the turbines.<br /><br />I don't know. I have only worked on pressure fed hypergolic systems. <div class="Discussion_UserSignature"> <p><strong><font color="#ff0000">Vote </font><font color="#3366ff">Libertarian</font></strong></p> </div>
 
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nacnud

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Trying to imagin this makes me think of a turbofan, or maybe a turbojet, is that similar to how this works?
 
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barrykirk

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Thrust to weight ratio is very important.<br /><br />A high thrust to weight ratio engine can carry more fuel or a larger payload.<br /><br />Remember that one of the biggest advantages, but not the only one that RP-1 has over LH2 is that for the same engine design. RP-1 has a higher Thrust to Weight ratio. Simply because of the higher density of RP-1. If you can increase the T/W ratio of the engines, than you make LH2 a much more attractive fuel.
 
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larper

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Well, it could be, but I am still confused. Correct my mistakes...<br /><br />In a turbo-fan, the combustion drives the turbine. The turbine is used to drive a fan. The fan brings in air to a)be used in the combustion process, and b) to be thrown out the back to produce thrust.<br /><br />It turns out that the most efficient jets are high-bypass turbo fans, right? In those, most of the air used to produce thrust DOESN'T go through the turbine, it bypasses it.<br /><br />In turbo jets, like in fighter planes, where efficiency is sacrificed for performance, most of the air DOES go through the turbine. The amount of air that goes in is huge compared to the amount that gets combusted. In a simplistic way, the air is a big piston (plus the verturi effect), and it is the air being pushed out, not the combustion, that provides thrust.<br /><br />A rocket is not quite the same. The fuel and ox are being combusted to provide thrust. In other words, there is no working fluid. You need high pressure of the fuel and ox in the combustion chamber to force the combustion products out the other way. The turbo pumbs create this high pressure, right?<br /><br />But they now want the fuel and ox to drive the pumps (not just pass through them) to create the high pressure. Just seems counter intuitve to me. <br /><br />Can a real rocket scientist explain this to me? <div class="Discussion_UserSignature"> <p><strong><font color="#ff0000">Vote </font><font color="#3366ff">Libertarian</font></strong></p> </div>
 
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dmc6960

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This may be a little off-topic, but has anyone made an engine that uses more than 2 liquids? This is probably very inefficient, but what would happen if your throw LOX, LH2, RP-1, and LNG all together at once?
 
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drwayne

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A mess that doesn't burn or perform very well. <img src="/images/icons/wink.gif" /><br /><br />Seriously though, there are of course proposals for some combinations, usually something like a double oxidizer like Flourine with LOX - also known as FLOX.<br /><br />Wayne <div class="Discussion_UserSignature"> <p>"1) Give no quarter; 2) Take no prisoners; 3) Sink everything."  Admiral Jackie Fisher</p> </div>
 
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dobbins

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Using Flourine as an oxidizer is one of the crazier ideas that some in the space comunity have come up with. Flourine is highly corrosive reacting with most metals so expensive containers are needed to store it. If Hydrogen is used as the fuel the resulting product is HF which is also highy corosive and that substance reacts with water to form Hydrofluoric acid, which is so corosive it even disolves glass.<br /><br />The exhaust from a rocket using flourine would be a major health hazard so it's never going to be used.<br />
 
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barrykirk

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Actually the highest ISP chemical rocket I've ever heard of uses Lithium, Hydrogen, and Florine.<br /><br />As pointed out the exhaust is toxic and environmentally hazardous as well as being extremely corrisive to the engine components.<br /><br />The advantages in ISP are too minor to justify the environmental damage.
 
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dobbins

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The exhaust of a Rocket that used fluorine as it's oxidizer would be deadly enough to qualify it as a chemical agent WMD.<br />
 
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drwayne

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Actually the proposals I have seen for FLOX involved upper stage use in which the engines in question were only used in space.<br /><br />A 50/50 mix of Flourine and LOX is manageable from a piping standpoint, if still extremely harzardous.<br /><br />I have used HF by the way, to etch quartz ampoules. It is hazardous for sure, but I did manage it. <img src="/images/icons/wink.gif" /><br /><br />Wayne <div class="Discussion_UserSignature"> <p>"1) Give no quarter; 2) Take no prisoners; 3) Sink everything."  Admiral Jackie Fisher</p> </div>
 
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starfhury

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Correctly me if I am wrong, but the point of pushing the fuel and oxidizer through the turbopumps is to increase chamber pressures. With more or all the prop flowing through the preburner, the actual prop flow rate into the combustion chamber can be lowered increasing mileage so to speak. Once in the chamber, the higher pressure promotes greater mixing of the fuel and oxider for an even more efficient thorough burn producing more thrust. The net benefit being less prop used for the same or higher thrust produced. One of the downside of course, is can you build a combustion chamber strong enough and also light weight which can still stand up to the enormous chamber pressures? <div class="Discussion_UserSignature"> </div>
 
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larper

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<blockquote><font class="small">In reply to:</font><hr /><p>Good beginning, but you started getting off-track here: <p><hr /></p></p></blockquote><br />Yeah. That was all my understanding as well, just wasn't able to articulate it goodly. <div class="Discussion_UserSignature"> <p><strong><font color="#ff0000">Vote </font><font color="#3366ff">Libertarian</font></strong></p> </div>
 
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