UK government invests in Sabre air-breathing rocket engine

http://www.bbc.co.uk/news/science-environment-23332592

by andydd • 13 years ago

88 57 13 years ago

bbc.co.uk

eksith• 13 years ago

This is a dubious investment IMO.

Rockets that have shrouds have been thrown about for a long time, but they have one fundamental weakness. The shroud only works while in the atmosphere. After that, it's dead weight (since no significant aerodynamic forces come into play further up).

It's not quite the same as the SR-71 Blackbird engine which is a turbojet engine that morphs mid-flight into a ramjet. That's quite a spectacular piece of engineering especially since this was before the advent of computer-aided modeling. But the SR-71 was still very much an air breathing engine. The outer engine casing was still an essential part of its function.

Don't get me wrong; I wish these guys success and I hope my assessment is incorrect, but I just don't see how added weight to win over gravity lower in the atmosphere would help in the upper atmosphere and in space.

NickPollard• 13 years ago

I don't know the maths involved, but the idea presumably is that they save more weight not carrying (as much) oxygen than they lose by adding the rest of the engine. By being able to draw oxygen from the air whilst in the atmosphere, they only need to store a smaller amount of oxygen for when they hit space. This is the main saving I believe.

pja2• 13 years ago

Indeed. O2 is much heavier than H2 so if you can scavenge the O2 out of the atmosphere on the way up then the amount you need to carry for the final burn in space is much smaller & the weight savings are huge.

Consider that the Space Shuttle external fuel tank contained 650,000kg of O2 and only 100,000 kg of H2. Save 10% of your O2 needs and suddenly you've got 60,000 kg to play with. The Shuttle payload was only about 25,000 kg.

chromaton• 13 years ago

There's also the drag effects to worry about which pure rockets don't have to deal with.

This engine could end up being useful in the long run, but the clear path to cheap access to space involves reusability, and a more complex motor works against that.

stcredzero2• 13 years ago

However, the ability to avoid staging is also a huge win.

disputin• 13 years ago

It'll be fine - "Mr Osborne himself has inspected the test rig"!? The UK gov will jump at any potential economy booster ('scuse) right now.

cpleppert• 13 years ago

There are a lot of weaknesses in the design that haven't been worked out regardless of the technical merit of the engine. Reusable vehicles are tremendously expensive and Sabre has to peform perfectly not only on the engine but the vehicle as well to get any return on its investment.

Although the sabre is more efficient operating in the atmosphere than a conventional rocket engine the vehicle itself will have to spend the cost of having wings, strengthening the vehicle to operate in several orientations on ascent, operating in the atmosphere for longer than a conventional rocket(which costs fuel and requires the vehicle to be shaped in a way that just isn't as efficient as a conventional rocket), and being able to withstand reentry temperatures(more weight) not to mention not being able to get rid of dead weight on ascent. The reusable components of the engine also weigh a lot more as well. If you go through everything it doesn't look like that great a win; and that is if everything works perfectly.

The space shuttle never came close to its projections and this vehicle is far more technically ambitious in every possible way. I just don't think that their projections of even $10-15 billion in development costs are even remotely realistic. Last time I checked their business plan suggested they could break even if satellite launch costs didn't come down and the volume of launches of large satellites increase.

timw6n• 13 years ago

A couple of months ago there was an excellent BBC4 documentary about Alan Bond and Reaction Engines called The Three Rocketeers[1], which I believe has been re-posted on the internet.

http://www.bbc.co.uk/programmes/b01mqv45

Element_• 13 years ago

It was an excellent documentary: http://www.youtube.com/watch?v=vZ_a21fPkYM

tobiasu2• 13 years ago

How and where does the nitrogen boiler(?) get its energy too cool helium to -170C at a constant rate? Is it effective to chill what must be ginormous amounts of air to -150C? It's all nice that the heat exchanger works, but where does that heat go?

There's a large discrepancy between the inlet air temperature (1000C vs 20C) in the article.

Somehow my sense for violation of the laws of thermodynamics is tingling.

pja2• 13 years ago

In the tests it's presumably just a continuous flow of pre-cooled liquid nitrogen from a tank & the heated N2 is probably dumped into the environment.

The design for a flight-capable engine is supposed to dump the waste heat into the fuel I believe.

arethuza7• 13 years ago

They have details on their web site:

http://www.reactionengines.co.uk/sabre_howworks.html

My reading of their explanation is that in a full system they would "pre-burn" some of the hydrogen and oxygen also used to power the main rocket motor to power the cooling of the helium that then cools the intake air.

[NB I have no idea whether that would actually work or not - just trying to interpret what their own explanation is!]

tobiasu2• 13 years ago

Thanks for the link, this clears up a lot: http://www.reactionengines.co.uk/images/sabre/sabre_cycle_10...

There is no nitrogen in the system (not as consumable, anyway). Shoddy BBC reporting, as usual.

The heat exchangers use chilled hydrogen fuel they have to take up anyway, before it is burned in the rocket motor.

That makes a ton more sense.

33273• 13 years ago

The Brits are good engineers, and, compared to American juggernaut companies, specially in the defense and aerospace area, they manage to make innovation with very little.

The US military spent millions all through the 1960's upto the late 1980's for a successful VTOL aircraft. Along came the brits with fractions of the budget with a great product the Harrier GR-1.

There are some great arguments here, specially the savings in weight from Oxygen by pja.

But I want to ask something different. Even if there is a slight chance for this idea to succeed shouldn't we/they invest in it anyway? Making breakthroughs in jet engine design takes years and extraordinary amount of effort and money. If the government doesn't take the risk, long term innovation would be very difficult. Plus even if it doesn't reach its intended goals many side technologies are generated even from a failed undertaking...

arethuza7• 13 years ago

Also the TSR-2 - which was a fantastic aircraft design:

http://en.wikipedia.org/wiki/BAC_TSR-2

"All modern aircraft have four dimensions: span, length, height and politics. TSR-2 simply got the first three right."

33273• 13 years ago

wow what a beauty !

moogleii• 13 years ago

It's hard to say how much of US defense/aerospace costs are due to..."overcharging" though. Also, it looks like the US had a hand in engine development for the initial experimental versions (P.1127). Costs were shared with West Germany as well (from harrier.org.uk). From the wiki:

By the end of 1958, barely eighteen months after the start of the project, all the main features of the P.1127 were developed with one exception, the reaction control system - this was resolved by April 1959.[6] As the P.1127 had been developed at a time of deep UK defense cuts; Hawker had to seek commercial funding, significant engine development funding came from the U.S.[4][7] Wind tunnel tests conducted by NASA Langley Research Center using a sub-scale model showed acceptable flight characteristics.[4][8]

I'm not sure how nimble and less wasteful NASA is, or even if it would be considered "cheap", but their X43A project costs were about 27 million 1958 British pounds ($230M US in 1997).

JonnieCache3• 13 years ago

If the government doesn't take the risk, long term innovation would be very difficult.

What I'm wondering is, if the taxpayers have to take all the risk and spend all the R&D money out of our own pockets, why don't we get to keep all the profits as well? I thought innovation was the role of heroic figures who eat risk for breakfast? I thought the massive, economy-distorting pay packages were justified by all that risk?

EDIT: obviously a lot more money is needed for marketing, manufacturing etc. But as I understand it the IP from these projects is basically given as a gift to favoured arms manufacturers when it's ready to become a product? Please correct me.

arethuza7• 13 years ago

The article says:

"the government's investment represents about 25% of the total"

Personally I am quite delighted to see my UK tax money going to back this project. Compared to the amounts we spend on much sillier projects it is a rounding error.

[e.g. My home city of Edinburgh is spending £1 billion on a rather short length of trams and the UK is spending ~£7 billion on two aircraft carriers when we can only afford to run one!]

33273• 13 years ago

You are absolutely right. I am no expert in IP or government affairs but I would imagine that stakes in the project become an issue and even though a fully working "final" product say version 1.0 for production might be ready, the investment necessary for production of such parts are massive.

Second to that is the know how and expertise in precision manufacturing for such products that require a high degree of reliability.

In addition to this continues R&D and investing must be done for problems and improvements.

In summary I guess the people "get" their "profits" in the form of an army/navy/space marines equipped with the latest air breathing rocket engine.

parley• 13 years ago

I seem to remember Elon Musk getting a question about SABRE at a post-talk Q&A a while back (probably in the UK, perhaps an inauguration ceremony of some institution), but now I can't find it. He was skeptical and had some constructive things to say, but I'm not a physicist so unfortunately I can't remember the specifics. If anyone else finds it, kindly reply with a link!

EDIT: Found the video, but haven't yet found the specific time of the question. My connection is a bit slow, so jumping around in the stream isn't going so well. http://www.oxfordmartin.ox.ac.uk/videos/view/211

EDIT 2: Found it. Elon's reply is at 48:55.

arethuza7• 13 years ago

Maybe he doesn't like it because it won't work on Mars? :-)

speeder2• 13 years ago

Whoa, this is really awesome!

For those that don't know, airbreathing engines are MUCH MORE efficient than conventional rocket engines.

Not only in terms of weight saved from not having to lug around too much O2, but also because of the way it works inherently.

I decided to make a space game once, with real world stuff on it, and settled for the Triton engine for my game spaceship, I did lots of research about rocket engines, and I was very sad when I compared them to airplane engines and it was clear how better they were, and yet useless in space.

But I never had this idea of mixing both... It sounds so awesome that I cannot describe it.

Also it allow some sci-fi stuff that is frequent but so far very broken (that is small fighter spaceship planes hybrids that can enter and leave atmosphere at will, that for now were usually handwaved by the author to explain that it has some weird super efficient rocket engine... with this tech that sort of stuff is less improbable)

stcredzero2• 13 years ago

Not that much of a handwave, if you allow for energy storage as light and compact as antimatter. Engineering such a craft the size of a fighter might be quite difficult, though.

benl• 13 years ago

Are they really more efficient, for real world uses?

The way I understand it, the argument goes something like this. To reach orbit you need to accelerate to very high speeds (Mach 25). To avoid crazy drag losses you therefore want to get out of the atmosphere as quickly as possible. So being able to use oxygen from the air on your way up is a marginal gain at best, and almost certainly not worth the extra complexity.

willvarfar• 13 years ago

Maybe they make most sense for military missiles?

nemof• 13 years ago

The primary benefit is weight reduction:

http://www.reactionengines.co.uk/sabre_howworks.html

This approach enables SABRE-powered vehicles to save carrying over 250 tons of on-board oxidant on their way to orbit, and removes the necessity for massive throw-away first stages that are jettisoned once the oxidant they contain has been used up, allowing the development of the first fully re-usable space access vehicles such as SKYLON.

speeder2• 13 years ago

You need to avoid drag losses if you are not using air in first place, because then any drag losses is wasted fuel and reaction mass.

But if you are using a air turbine, you can attempt to make it more economical than the losses from drag and extra machinery weight.

This is more for some type of missions though, if you wanted to make a rocket to pluto, then probably the extra weight is bad, but for a orbital space shuttle this is awesome.

I see the optimal path for long term exploration is use such turbine/rocket hybrids to build orbital shipyards, and then use those shipyards already in the orbit to build pure-rocket ships for missions that don't need to start on the planet (like a voyager-like exploration mission, or launching a hovercraft scout to gas giants...)

olex• 13 years ago

The main advantage of the Sabre concept is not only using outboard air as substitute for onboard oxidizer, but also as reaction mass. This allows to accelerate to over Mach 5 while still flying in airbreathing mode, using a fraction of the amount of fuel that would be required to reach the same speed on pure rocket power, and no onboard oxidizer. Once that speed is reached, the air becomes too thin for the air-breathing mode to continue functioning, and the engines switch to rocket mode, burning onboard oxidizer instead of air; but because the ship is nearly out of the atmosphere at this point, it doesn't take much to finish accelerating to orbital speed. Think of it basically as replacing the whole first stage of a conventional rocket with some jet engines and a sip of fuel for them.

ianstallings• 13 years ago

My understanding is that a lot of the energy used to get to space these days is to get through the lower atmosphere. The idea of a space plane is to fly higher to the thinner atmosphere and then begin the ascent to space, avoiding the energy loss used burning through the entire troposphere. If you can fly to 5-6km you just took off a significant amount of total energy cost. Then you crank these babies up and fly to mach 5 and launch your payload or maybe the craft itself using rockets. Because you already got 1700 m/s already to start with.

And to answer the obvious question yes I have been playing entirely too much Kerbal Space Program.

Retric• 13 years ago

The end product from a hydrogen fueled rocket is H2O. Of which oxygen represents 88.8% of the weight so there is a lot of weight savings available to make up for the increased drag and a more complex engine design. Also of note you need to accelerate not just the ship and cargo but also all that unspent fuel so weight savings tend to multiply.

An air breathing rocket that hit's Mach 5+ means on the order of 30% less fuel and less structure to support that fuel. Which not only allows for more cargo but significantly more redundancy and a much higher structural safety margins.

moocowduckquack• 13 years ago

I think you may have it back to front. To avoid crazy drag losses you cruise the lower atmosphere, then kick to high speed once into much thinner air.

simcop2387• 13 years ago

If you want to play with space games that'll let you do that check out Kerbal Space Program. Might still be on sale on steam.

If they can get it off the ground this could easily make things so much easier to get into LEO, since the main engines wouldn't have to carry around half the equation it'll mean much higher thrust to weight ratios, which means cheaper, and then you could have a much smaller craft increase it's orbit with smaller engines and a much lower delta-v than is needed to reach orbit normally. Take that and add a single larger setup that'll get large heavy things in orbit (we've got that now with modern rockets) and you could leave a station in orbit that could act as a bit of gas station for the smaller ones. That alone could make moon transits far more economical, though it still leaves the problem of what do you do when you get there, the resources available aren't incredibly valuable or anything.

VladRussian2• 13 years ago

since the main engines wouldn't have to carry around half the equation it'll mean much higher thrust to weight ratios

on the other side you need energy to wastefully slow down with respect to the aircraft frame (i.e. provide delta-v to) 80% of the outside air - nitrogen - you scooped. Engines without slow down of the air mass - scramjets - are different beasts and have their own issues).

Thus you have choice - carry with you and speed up 1 lb of O2 to the speed of 5 Mach or slow down from 5 Mach (slow down is the same energy consuming action as speed up) 4 lb of nitrogen and 1 lb oxygen of the outside air.

venomsnake3• 13 years ago

I am a bit skeptical of any technology that uses helium. We just don't have viable ways to obtain reliably enough of the stuff reliably.

maxerickson• 13 years ago

It doesn't look like it consumes it. So we could probably build hundreds or thousands of these things without much trouble.

DuskStar2• 13 years ago

As far as I can tell, the production version will use LH2 instead of Liquid Helium to cool the incoming air. (after which the Helium will be burned for thrust, no need to cool it back down)

It's a similar to how most rocket engine nozzles are cooled.

arethuza7• 13 years ago

Well, there is an expensive plant in France that will be manufacturing helium from raw materials ;-)

http://www.iter.org/

venomsnake3• 13 years ago

Nuclear fusion has always been 10 years away. Lets hope that they will succeed this time.

jotm• 13 years ago

Man, I really hope this engine works - they won't get a second chance if the prototype fails (which is a shame, since the concept is solid)...

And that prototype plane/spaceship just looks cool as hell...

lifeisstillgood• 13 years ago

This made my day however:

  has passed an independent audit from European Space 
  Agency experts, and Mr Osborne himself has inspected the 
  test rig on the Culham science park in Oxfordshire.

The ESA has verified the engine, but thank goodness, George Osbourne double checked it all, just in case those rocket scientists missed micro-fluctuations in heat transfer gradients. I mean they were probably all French anyway.

George Osbourne (UK CFO/Treasury Secretary) is getting a lot of political flack, and having his name associated with UK home grown and based innovative technology is clearly something his press office wanted the BBC to know. Who were too lazy to cut the sentence.

colinm• 13 years ago

"Do you have one in green?"

lmm• 13 years ago

What are you talking about? The only thing I can think of is British racing green, and that's a bit of a stretch.

voicereason2• 13 years ago

You clearly have something against Osborne.

The UK government are investing the money. Osborne is the Chancellor of the Exchequer, why is it strange that he would be mentioned in the article as having a look at it?

He's only getting political flak from socialists and welfare claimants really - no surprise there.

JonnieCache3• 13 years ago

And those well known socialists, the IMF: http://www.guardian.co.uk/politics/2013/apr/18/george-osborn...

ris2• 13 years ago

1. Everyone's a socialist, so using it as a pejorative doesn't really work.

2. There aren't enough "welfare claimants" in this country to really have a big influence on anything themselves. The vast (vast) majority of people claiming benefits are hard working people who do 40 hour weeks but still don't earn enough to support their family, so they claim Working Tax Credits. This was Thatcher's doing, by the way.

acd• 13 years ago

Sabre Air will eventually revolutionize internet communication so that it is possible to get internet access cheaply anywhere on earth.

Commstellation a Canadian company are planning 72 micro satellites that will provide backbone capacity for cellphone towers. Latency will be in the 40 ms range. http://www.commstellation.com/

Currently smartphones become dumb phones as soon as you leave your country on vacation, in the future we will be able to connect to internet anywhere cheaply.

jpeg_hero• 13 years ago

The british are cute.

that test rig looked like something the North Koreans would put together.

this is no where near being a "real program"

UK government invests in Sabre air-breathing rocket engine

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