Hacker News Board Hacker News, browsed like a classic message board
Live data from Hacker News

British aerospace company claims biggest engine advance since the jet

uk.reuters.com

Post reply on HN
Print view View original

61–70 of 109 posts

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

#61

Post by iRobot »

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…

As far as I can see the plan seems to be to create a blueprint engine/rocket which can be sold on the open market, this company seems happy with just making the "pre-cooler" part of it. I suppose the analogy is like Intel making the processor and anyone can make improve on the motherboard/PC

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

#62

Post by robomartin »

stcredzero wrote: post #48
schiffern wrote: post #43

Earlier quoted context omitted.

The payoff would be immense though. At datacenter electricity prices, the fundamental energy cost to LEO is about 50¢/kg.

Fuel (energy) cost is less than 1% of the cost to launch. The big costs are manpower, maintenance, and refurbishment.

I don't know the first thing about orbital-scale rocket economics, so, please, regard this as complete and utter speculative nonsense.

My thinking is that, if there's a future where we might have regular launches to orbit all of those costs will have to drop. At that point fuel might just start to become far more significant.

Let's imagine weekly "Orbit The Earth Adventure"(TM) launches in 25 or 50 years. The spacecraft, crews and maintenance would have to be optimized in order to enable the business model. I think it could very well be in that context that a MAGLEV launch-assist vehicle might make sense.

Again, I don't know what I am talking about and don't really have the time to research the subject and learn about the economics of low-earth-orbit manned space flight. I'll just have to leave it at that.

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

#63

Post by ricardobeat »

stephengillie wrote: post #56
tompko wrote: post #26

Earlier quoted context omitted.

> while this can only be useful where you still have atmosphere and oxygen The planned SABRE engine can act as a rocket as well closing the intake and using stored liquid oxygen so it would be capable of operating without an atmosphere and oxygen and landing on Mars.

Can it take off from Mars? In another HN thread a month ago, we discussed how Mars' atmosphere is so thin that a Cessna would need 747 wings and near Mach 1 velocity to take off.

Rockets are propelled by their own exhaust.

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

#64

Post by EthanHeilman »

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…

Elon didn't directly address the advantage of the Skylon (he said he hadn't really looked into it, so fair enough). The main advantage is not that you don't need to bring oxygen for a portion of our trip (which as Mr. Musk points out wouldn't really save very much), but rather that you don't need to bring reaction mass.

Jet engines are just really really fast propellers. They don't need to carry their own reaction mass like a rocket. This gaves them a completely different efficiency profile (no reaction mass, means less weight, which means less fuel, which means less weight, rinse/repeat to the limit). This is the reason that 747s use jet engines rather than rockets. Being able to use both technologies fluidly within their optimal atmospheric envelopes would be a major breakthrough and would completely change access to space.

tl;dr Skylon can use a small, efficient jet engine to get high and fast enough that air resistance stops mattering and while slowly pivoting to a conventional rocket (which is optimal when the air gets thin).

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

#65

Post by iwwr »

russss wrote: post #29
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…

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

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

#66

Post by starpilot »

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 fair to compare it to the jet when RBCC isn't a fundamentally novel form of propulsion, just a combination of existing ones (like a car that is both gas and electric propelled). This is not something that could supplant the jet.

Some people are comparing this to SpaceX's pure-rocket approach. Up until yesterday, SpaceX and Scaled were working on their own type of combined-cycle launch with Stratolaunch: http://www.flightglobal.com/news/articles/stratolaunch-and-s.... The difference is that the jet and rocket would be separate vehicles instead of fitting into one nacelle. It'd have some of the advantages of using air as propellant as with a RBCC engine, but easier to design I think.

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

#67

Post by wololo »

stephengillie wrote: post #56
tompko wrote: post #26

Earlier quoted context omitted.

> while this can only be useful where you still have atmosphere and oxygen The planned SABRE engine can act as a rocket as well closing the intake and using stored liquid oxygen so it would be capable of operating without an atmosphere and oxygen and landing on Mars.

Can it take off from Mars? In another HN thread a month ago, we discussed how Mars' atmosphere is so thin that a Cessna would need 747 wings and near Mach 1 velocity to take off.

fyi: https://news.ycombinator.com/item?id=4261806, https://news.ycombinator.com/item?id=4608595

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

#68

Post by FrojoS »

EthanHeilman wrote: post #64
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…

Elon didn't directly address the advantage of the Skylon (he said he hadn't really looked into it, so fair enough). The main advantage is not that you don't need to bring oxygen for a portion of our trip (which as Mr. Musk points out wouldn't really save very much), but rather that you don't need to bring reaction mass. Jet engines are just really really fast propellers. They don't need to carry their own reaction ma…

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.

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

#69

Post by drzaiusapelord »

tvon wrote: post #53
drzaiusapelord wrote: post #35

Earlier quoted context omitted.

Funny how this stuff works. The hot whiz-bang kid rewriting all the rules can become tomorrow's rent-seeking cronyistic old guard overnight. I wonder if a rocket vs sabre engine war is about to start. I hope so. Easier access to orbit and a 4 hour trip from NY to Tokyo would be pretty amazing.

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.

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

#70

Post by [deleted] »

robomartin wrote: post #41

The MAGLEV Launcher. http://en.wikipedia.org/wiki/Rocket_sled_launch http://www.reallyrocketscience.com/node/2393 Using MAGLEV as a launch assist technology to offset the amount of energy derived from burning tons and tons of fuel. Some of the articles estimate a potential to increase payload by 80% compared to a conventionally launched rocket. If you want to get a little deeper into it, this is a good read: http://u…

[deleted]
Post reply on HN