New Rocket Engine Successfully Tested

inetsee writes "XCOR Aerospace announced that their new methane-oxygen rocket engine has been tested successfully. This is reported to be the first successful test of an engine using the combination of methane and oxygen as fuel. The fuel has higher specific impulse than kerosene and oxygen, but until now has been thought to have too much 'technology risk'."

Comments

Little bit disingenuous

[AKAImBatman]

The fuel has higher specific impulse than kerosene and oxygen, but until now has been thought to have too much 'technology risk'

There hasn't been much use, because rocket design has been on a different track than XCOR. Kerosine engines are primarily used for their high thrust to weight ratios, which help get a rocket off the ground. Once the rocket is in flight, the first stage is usually dropped in favor of a more powerful engine, such as Liquid Hydrogen/Oxygen engines. LHOx has the highest specific impulse of any fuel deployed to date; even more efficient than the methane-oxygen engines they're proposing.

The problem is that XCOR is working on a different track than NASA and the large rocket manufacturers. They're focusing on winged takeoff and landing, where high thrust to weight ratios aren't as important, and can be sacrificed for greater efficiency. (For comparison, the kerosine F-1 engines on the Saturn V produced 1.5 million lbf compared to the 7,500 lbf targetted by this engine.) So the methane-oxy engine development has less to do with politics, and more to do with the practical matters of meeting the targetted design goals.

Re:Little bit disingenuous

[AKAImBatman]

I don't see what their target thurst is, but one can assume it's much larger than 7,500lbf.

7,5000 lbf is the target for this engine. It builds upon the 50 lbf XR-3M9 and 10,000 lbf 5M12. As pointed out by another poster, XCOR claims "the new Orion Crew Vehicle main engine design will be an interpolation between these recent designs."

Additionally, XCOR is advertising their engine developments as a possible base for methane-breathing Jet engines that would work in Mars atmosphere. (A very interesting development, indeed!)

BTW, if you have the projected thrust to weight ratios, please share them. I hate having to use the thrust values, because it can be (as you said) misleading. Unfortunately, I don't have the values for the XCOR engine. What I can say is that LHOx > methane > kerosine in terms of specific impulse/efficiency. In terms of thrust to weight, the formula is exactly reversed where kerosine > methane > LHOx. There are very few cases where both the thrust to weight and specific impulse are high. (Orion Project and MPD thrusters are the two I'm aware of.) Otherwise, they tend to be inversely proportional.

Mars exploration

[hypermanng]

By far the most critical aspect of this for me is its practicality for use in Mars exploration or, more to the point, colonization. While it's obviously too soon to colonize anything at a reasonable price (and real colonization will only occur when we can get some prospect of a return commensurate to the colossal investment) but the sooner the requisite technologies enter wide use, the sooner their price starts to drop, the more hospitable the cost/benefit balance sheet begins to look. Little things like this could make ten years worth of difference.

No

[everphilski]

So the methane-oxy engine development has less to do with politics, and more to do with the practical matters of meeting the targetted design goals.

No, it has more to do with the subcontract they have with ATK to do research for NASA LINK. This pays the bills while they play with their winged rocket-plane.

For comparison, the kerosine F-1 engines on the Saturn V produced 1.5 million lbf compared to the 7,500 lbf targetted by this engine.

They were also pumping a lot more fuel and oxidizer per second (much larger m_dot). This is a small engine mounted to the back of a trailer. You could (almost) wrap your hands around it. The F-1's chamber is quite a bit bigger.

Re:No

[AKAImBatman]

No, it has more to do with the subcontract they have with ATK to do research for NASA LINK.

Good catch. But it's still not being developed for a traditional launch system. According to their website, this engine would be used for the lunar -> LEO transfer stage on the CEV. Which again makes the thrust to weight ratio less important, and again non-comparable to kerosine engines. (From what I understand the Apollo Service Module used a hydrazine engine for the transearth injection.)

They were also pumping a lot more fuel and oxidizer per second (much larger m_dot). This is a small engine mounted to the back of a trailer. You could (almost) wrap your hands around it. The F-1's chamber is quite a bit bigger.

Agreed. However, I don't have the actual Thrust to Weight ratios for the XCOR engine, so all I can do is point out the differences in their thrust. If you have the actual ratios, feels free to chip in.

Armadillo too is considering methane

[YA_Python_dev]

Armadillo Aerospace is considering exactly the same fuel. Some of the advantages are relatively high ISP (lower that LH2, but with a much smaller volume) and the fuel and the oxidizer (LOX) have more or less the same volume which can be a very good thing, depending on your vehicle configuration.

Re:Why hasn't it been worked on?

[everphilski]

Someone I know refers to it a "cow-milker" :-P

I think it is interesting, huge weight savings over a pressure fed with none of the high-speed parts of a turbopump. Flowmetrics wasn't the first to come up with the idea although they were the first to put it on a rocket and have patented several ideas relating to it. I'd like to see it running in a bigger concept than the SDSU rocket though. (Steve and Carl, faculty advisors for the projects work at Flowmetrics)

(They were pumping martinis at the Joint Propulsion Conference 2 years ago... very nice... and yummy)

Re:Risk?

[Kamots]

Different kind of risk.

The risk being talked about here is program risk... ie... the risk that using unproven technology will result in cost and schedule impacts to the project due to unforeseen problems. Not the risk of things going boom (although that can impact cost and schedule too... XD) Using proven, well-understood technologies reduces risk.

Think of it this way... if you're given a task to develop a program for $C dollars inside of Y months, are you going to use a well-established programming language or are you going to go with some new half-developed (but really nifty) one where you're playing debug the compiler as you work on your project?