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British aerospace company claims biggest engine advance since the jet

uk.reuters.com

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Re: British aerospace company claims biggest engine advance since the jet

#81

Post by [deleted] »

Gravityloss wrote: post #78
starpilot wrote: post #66

This is just rocket-based combined-cycle propulsion that has been proposed and studied by various organizations over the years. http://en.wikipedia.org/wiki/Rocket-based_combined_cycle http://investor.gencorp.com/releasedetail.cfm?ReleaseID=7085... http://www.isset.org/nasa/nano/www.grc.nasa.gov/WWW/AERO/bas... The concept is not new, but Reaction is probably the closest to a commercial implementation. Also, it's not…

The precooler / heat exchanger is the SABRE's distinction. Ramjets and scramjets don't have such. It enables low internal gas velocity and small compressors and more thrust from a smaller engine and higher top speed than jets. It's like saying when the Wankel was invented that "it's just another internal combustion engine". Sure, it is, but it's quite different from most of the others.

[deleted]

Re: British aerospace company claims biggest engine advance since the jet

#82

Post by [deleted] »

jws wrote: post #25

The BBC article, http://www.bbc.co.uk/news/science-environment-20510112 has some nice explanatory graphics. It appears they are using a liquid nitrogen boiler to chill a helium loop through their heat exchanger and in turn chill the air. So, perhaps someone better at these calculations can help out, cooling incoming air by 160°C by moving nitrogen from -195°C to -15°C is going to require them to haul up liquid nitrog…

[deleted]

Re: British aerospace company claims biggest engine advance since the jet

#83

Post by fleitz »

jivatmanx wrote: post #20
mtgx wrote: post #5

Elon Musk was specifically asked about this technology when he was at Martin School last week. He didn't hear about it, but he seemed skeptical that it would work better than rockets. His response here: http://youtu.be/c1HZIQliuoA?t=48m55s SpaceX might still be the first one with a re-usable rocket if they finish the Raptor engine in 3 years. Plus, his could actually be used to land on Mars, while this can only be us…

You might be able to use this engine to get in and out of orbit, and than use a traditional rocket engine for the space travel itself.

More importantly (for intra-planetary travel) if you can get close to escape velocity then you spend most of the flight time in a near zero resistance environment which dramatically improves fuel efficiency as well as significantly reducing flight time.

Re: British aerospace company claims biggest engine advance since the jet

#84

Post by jasonwatkinspdx »

starpilot wrote: post #66

This is just rocket-based combined-cycle propulsion that has been proposed and studied by various organizations over the years. http://en.wikipedia.org/wiki/Rocket-based_combined_cycle http://investor.gencorp.com/releasedetail.cfm?ReleaseID=7085... http://www.isset.org/nasa/nano/www.grc.nasa.gov/WWW/AERO/bas... The concept is not new, but Reaction is probably the closest to a commercial implementation. Also, it's not…

It is combined cycle, but that does not mean it's equivalent to the RBCC design. There are several variations of combined cycle engines. RBCC is not a catchall. This is a refinement of the Liquid Air Cycle Engine concept that was researched by the US military in the 60's and the british in the 80's. The principal british investigator was Alan Bond, who is also the principal in Reaction.

It is appropriate to distinguish it from both jet engines and rocket engines because in the Brayton Cycle compression is adiabatic rather than diabatic in SABRE. I don't believe there is a formal term for this cycle, but the closest existing would be the Ericcson Cycle.

I do not understand your preoccupation with whether to categorize something as novel or not. The have a chiller that drops the temperature of a near supersonic air flow over 1000C in a fraction of a second. If that doesn't meet your standards of novel I don't know what would.

Re: British aerospace company claims biggest engine advance since the jet

#85

Post by jasonwatkinspdx »

InclinedPlane wrote: post #79
mtgx wrote: post #5

Elon Musk was specifically asked about this technology when he was at Martin School last week. He didn't hear about it, but he seemed skeptical that it would work better than rockets. His response here: http://youtu.be/c1HZIQliuoA?t=48m55s SpaceX might still be the first one with a re-usable rocket if they finish the Raptor engine in 3 years. Plus, his could actually be used to land on Mars, while this can only be us…

Here's why Elon Musk is more likely to be right: because fuel is cheap. The cost of fuel and the cost of fuel tanks is an insignificant part of the cost of an orbital launch, around the 1% level. The major drivers of cost are overall system complexity and manufacturing cost of the engines. And here's the big problem for a Skylon spaceplane, rockets are fairly simple systems whereas hypersonic airbreathing engines are…

In the SABRE design you can pick whatever transition point you like to move from air breathing to pure rocket operation.

Re: British aerospace company claims biggest engine advance since the jet

#86

Post by jasonwatkinspdx »

mtgx wrote: post #5

Elon Musk was specifically asked about this technology when he was at Martin School last week. He didn't hear about it, but he seemed skeptical that it would work better than rockets. His response here: http://youtu.be/c1HZIQliuoA?t=48m55s SpaceX might still be the first one with a re-usable rocket if they finish the Raptor engine in 3 years. Plus, his could actually be used to land on Mars, while this can only be us…

The only problem with Elon's response is that rockets will never be used for terrestrial transportation. SABRE might.

Re: British aerospace company claims biggest engine advance since the jet

#88

Post by gfodor »

drzaiusapelord wrote: post #69
tvon wrote: post #53

Earlier quoted context omitted.

I think you're forcing that narrative, the old guard does not tend to start out their statements with "I may have totally incorrect assumptions here, but...".

Maybe, but I imagine someone like Musk would be pretty good with rhetoric and knows if he utters the wrong things at a press conference it could lead to disastrous results for his companies. He's just being diplomatic because it pays to be diplomatic.

Or, you know, he could actually just be telling the truth in saying that he is willing to concede he may be wrong on the issue if his assumptions are wrong.

Re: British aerospace company claims biggest engine advance since the jet

#89

Post by felixfurtak »

iwwr wrote: post #65
russss wrote: post #29

Earlier quoted context omitted.

The liquid nitrogen is just used for the ground tests. On the Skylon itself, this cooling capacity will come from boiling the liquid hydrogen fuel.

Skylon would basically use the cryogenic fuel as a giant internal heat sink. A more fanciful application of the concept: http://tvtropes.org/pmwiki/pmwiki.php/Main/StealthInSpace

How is this different to HOTOL ?

Re: British aerospace company claims biggest engine advance since the jet

#90

Post by bathat »

EthanHeilman wrote: post #73
FrojoS wrote: post #68

Earlier quoted context omitted.

Thanks for the description. So for a conventional rocket, like a Flacon 9, how much of the overall energy used is due to air friction? I would have thought, its just a small fraction.

According to this link ( http://www.g2mil.com/high.htm ), air friction is not completely trivial. Additionally rocket engines are more efficient in less dense atmosphere "because the thinner air allows a better plume". They estimate that launching from 30,000 feet provides 9.3% greater thrust. Note that much of the energy spent for orbital flight is not spend getting height, but spent getting speed. Efficiency is gre…

>LEO requires about 7.8 km/s, Skylon's jet engines can go around 1.7 km/s. You are reaching 20% of your orbital velocity without reaction mass.

Unfortunately, kinetic energy scales as speed squared, so 20% of your orbital speed represents less than 5% of your orbital kinetic energy. To put this in perspective, the difference in gravitational potential energy between LEO and the earth's surface represents about 15% of your total on-orbit energy.

Now, it's true that an air-breathing engine doesn't need to carry reaction mass (and, sometimes, oxidizer), but the air engines add considerable complexity (which is always a bad thing) as well as weight (because you still need to carry a conventional rocket to finish orbit insertion). So what you need to do is ask how the weight penalty of the air engine compares to the weight penalty of carrying extra fuel in a conventional rocket (bearing in mind, of course, that there a pernicious positive feedback loops when scaling a booster).

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