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Reaction Engines has updated their site, and are making good progress, with an engine test expected by 2020. Their air-breathing engine technology has many possible applications, including use in a reusable first stage.

Scramjets are essentially limited to weapons, since they require another means to get up to speed and don't work at all in space.

As I said above, until a SABRE engine is flying we might as well be talking about the efficiency of flying carpets. The intercooler has been tested and apparently it works, so I'm hopeful that the engine design will work, but you never know until you actually fly.

The intercooler works, and so does the transition from air-breathing to LoX mode:

http://www.reactionengines.co....

Those are basically the two really crucial and untested bits. So, the exchanger works, and they've got a scaled down engine which produces lots of thrust, though it's bolted to a test stand.

You keep arguing as if the Lapcat A2 uses a conventional engine, which it does not. An entirely new thermodynamic cycle takes advantage of the extremely cold fuel to significantly improve efficiency. Rather than armchair speculation based on generalizations, I'm more inclined to trust the actual modeling done for these engines and aircraft, for which the numbers look very promising. The engines are based on SABRE, and the ESA is confident that the design is sound.

You keep arguing as if the Lapcat A2 uses a conventional engine, which it does not. An entirely new thermodynamic cycle takes advantage of the extremely cold fuel to significantly improve efficiency. Rather than armchair speculation based on generalizations, I'm more inclined to trust the actual modeling done for these engines and aircraft, for which the numbers look very promising. The engines are based on SABRE, and the ESA is confident that the design is sound.

The precooler heat exchanger is the only unique part of Skylon engines, the rest is regular turbomachinery. It enable an engine cycle that produces thrust at far higher altitudes and velocity than anything we have known before and it does it on a remarkably small amount of light weight hydrogen.

The AFRL decided recently that the engine would work as advertized, Airbus wants to build the airframe.

http://www.reactionengines.co....

Skylon, or something with similar performance is the only way economical power satellites can be made (that I know about).

I am thinking an air-breathing ramjet winged first stage would have more potential.
I assume that you know about Reaction Engines ?

Instead of trying to use Apollo-era designs, how about using something that is designed specifically to fly itself down? The Shuttle and DreamChaser addressed this problem quite well. Piloting a can doesn't work too well when you're going downwards.

When sanity prevails and Shuttle-like designs come back, perhaps space travel will improve. Until then, it's 1960's rehashes all around.

No production first stage has every landed propulsively, so they are not going backward to something that was done before. The Shuttle was more "refurbished" then reused. The main fuel tank was discarded. The booster cases were fished out of the water (how modern) and basically rebuilt. The main engines were removed after each flight and rebuilt. The tiles painstakingly inspected and repaired. It was a technological marvel but a financial disaster. The Dream Chaser is just the payload, not launch system. They planned to launch on an expendable rocket. So your examples are all non-sequitors, not "how to do it right."

"Flying back" is not really an option for a first stage booster. You'd need to add wings (more weight and drag, or complex mechanisms) and you'd need to add some sort of heat shield (more weight.) Propulsive landing requires more fuel (weight). The reentry burn itself acts as the primary thermal protection system (counterintuitive, but true.) It's a very elegant solution for recovering the entire first stage for reuse. And it's ridiculous that no major aerospace company was willing to pursue it. (There was the DC-X experimental rocket, but that was a government funded experiment which McDonnell Douglas dropped as soon as the "cost plus" gravy train left the station.)

Now if you love wings, then the right way to do that is probably something like Skylon, but it's a long way from flying and SpaceX is already forcing launch prices lower.

Not if you design your space plane right...

HOTOL technology has not been abandoned, it is now being actively developed for the Skylon unmanned space-plane by Reaction Engines Ltd.

http://en.wikipedia.org/wiki/S...

http://www.reactionengines.co....

http://www.youtube.com/watch?v...

FORGET about the whole re-usability thing - it just costs too much.

Shall not!

But then, it is British, so the chances of one being built are pretty negligible...

Well, that might not be impossible http://www.reactionengines.co.uk/

The Brits have been pushing this kind of technology for decades (remember HOTOL?) but it seems to take a while for it to get any traction. Shame really, the potential is staggering. The demise of Concorde had more to do with its introduction coinciding with the oil embargo, it was conceived in the days of cheap fuel and its high consumption would have been less of an (economic) issue. I don't see any such issues with a hydrogen powered engine since producing hydrogen doesn't absolutely have to depend on hydrocarbons. I wonder if investors are just scared off by the Concorde experience.

Well, that might not be impossible http://www.reactionengines.co.uk/

Just thought I'd point you in the direction of Reaction Engines ideas for a mission to Mars. Take a look at the detailed PDF and the movie.

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

No, dragon is NOT yet human rated, Heck it just flew once,and that dragon didn't even had the equipment to berth with the station, lets alone give humans the life support.
Cheese is a lot easier to launch that a human, trust me.

Don't get me wrong, Musk is on the right track. His dragon sure will became soon man rated, he will eventually launch sats.
I just want to note that I think he is overly optimistic, taking all the time about how he will launch a falcon 9 every 3 months, about mars, re-usability, etc, and yet, until now he just can launch just one rocket per year,

On the other hand, he has plenty of enemies. I even witnessed one myself. Many peoples that work for pork that nasa provides are really upset by his work, and try to spread the FUD about how unsafe his rocket is and stuff like that.
So I guess here really plays it safe.

So go SpaceX, go and just suceed.

BTW, it looks like you (slashdot readers) were right when you laughed about Skylon
I actually registered here on slashdot to express my opinion about it.
Yet almost year passed since their 'precooler' test supposed to start, and its not done yet.
They indeed probably just blow dust into investor's eyes.

Quantum computing is green go and lot of money is spent toward developing it
despite the fact that is very very unlikely to became practical.
But say something about skylon and you are bashed with 'it will never work, go ahead and sink your lifesavings..."
BTW, this blogger reports leaked photos of setup of their precooler test that is key to whole design, and will be done in 18 of June.

Exactly.
However, laws of physics are somewhat against us. Its damn hard to bring anything to Mach 25.
Its not even about gravity, Heck, using plain cannon, you can reach 180km, well above edge of space.
Take a look for example at skylon about which I posted in this thread.
It seems more or less possible, and already there are many investors. When they complete demonstration program, they will be given a lot of cash.
It about the fact that rockets are just the only proven way to access space, and we always will want a better horse, especially due to the fact that creating the 'automobile' of space is damn expensive.
If one were to prove that you can build the space elevator, launch loop, a space gun or whatever, regardless of costs it would be built.
Maybe a true spaceplane will be one.

The new (well anything new is well forgotten old) Skylon could really turn the space tourism in reality.
To be honest I am still sceptical of their plan, but who knows, that might succeed.
They say that only new technology they will use (and it increases performance of the engine enabling it) the precooler will be tested this June, and that they passed independent reviews by NASA and ESA.
Peoples also thought that won't be able to fly until sufficiently powerful engine (internal combustion) was developed.
Then it didn't take Wright Brothers long to create an airplane.

Killing Constellation might actually be the best thing for increasing the chances that a kid gets to fly in space. Constellation was going to lock us into a flight architecture that was not suitable for anything other than occasional grandstanding flights to the Moon or Mars. It was not suitable for the basis of a space economy or a scalable transportation system that could support a lunar mining base and orbital facilities to build solar power satellites, for example. NASA clearly doesn't have a direction to get people into space, but now that it's out of the way, maybe other efforts can get a toe hold. (NASA hasn't yet arrived at a formula for stimulating this, the COTS model was fundamentally flawed, but I suspect that perhaps as few as five more years of floundering, and buying rides from Russia, along with watching China and India get into space, will focus America on this problem.) Here are a few potential contenders:

Skylon
Mystery Lockheed Martin Test Program
Vulcan (DARPA)
SpaceX Falcon


Right now, there are too many disposable rockets, chasing too small a launch market. Most of the private efforts are not able to get sufficient funding for the sort of technology advancement which will be required to get the cost per pound in orbit down by much, which in turn is required if anything useful is gonna happen up there. A seldom-recanted but critical part of the X-33 story was that the business model for VentureStar fell apart. There were at least one, if not two satellite phone companies planning to orbit hundreds of telecom sats. They were looking for large buys, on the order of a flight per week, for years on end, of Shuttle-class payloads (50,000 lbs), and wanted lower cost per pound. When those companies looked like they were going to fail, the primary contractor concluded that the remaining launch market (NASA plus industry at roughly the level we see today) wasn't big enough to justify private funding for the VentureStar, even after they X-33 notorious technical issues were studied and believed to be resolvable.

It's been mentioned on /. before, but worth mentioning in this context: A UK company called Reaction Engines Limited is developing a reusable single-stage-to-orbit (SSTO) spacecraft. It is intended for exactly what NASA wants: Commercialized operations with rapid 2-3 day turnaround times and a high degree of reliability when compared to something like the STS space shuttle. It uses a very interesting hybrid rocket engine that is capable of breathing air up to 26-ish kilometers and a speed of mach 5.5 before switching to an on-board O2 supply for the orbital insertion. Reaction Engines Limited has been working on the design for over 20 years, and the design is basically a modern rework of an older design called HOTOL from the 60's. If anyone has $10 Billion, I'd highly recommend giving it all to these friendly people: http://www.reactionengines.co.uk/skylon_overview.html

Two things
Air breathing rocket engine wise can I introduce you to:
http://www.reactionengines.co.uk/sabre.html

I think the important thing with SS2 isn't about the technology itself it's about creating the market. Assume that they are successful as a small market - they'll soon enough get competitors who try and compete by building something better/cheaper. If they can't create the market then no harm done, if they can then the only way I can see it go is driving prices down and altitude/speed up.

Ah, yes, sorry, hydrogen is so hard to store and so dangerous, I forgot... Whereas nuclear reactors and bombs are so safe... http://www.reactionengines.co.uk/lapcat.html Oh yeah, and the Russians made this: http://en.wikipedia.org/wiki/Tu-155 The major problem is usually the sourcing of hydrogen - but that has been solved in this case. BTW are you two in some sort of anti-hydrogen lobby group or something? just curious...

Regular readers of my comments will know that I'm highly critical of NASA. However, it's important for enthusiastic supporters of space exploration to understand that private industry, left to its own devices, is not likely (is, in fact, extremely unlikely) to fund the R&D required to build the next generation of space transportation system. Getting to LEO is a big, big project. Much bigger than the trans-continental railways. Private corporations do not have the vision required for long term investment on this scale. They have quarterly numbers to meet, impatient and risk averse investors and managers.

The entire global investment in privately funded launch programs, if combined into a single program, is probably still a bit shy of appropriate funding for a single modern system, say, the Skylon program.

What we need is rational, visionary, intelligent and consistent policy, with consistent and rational funding to back it up. Governments, funding the next generation of launch systems required to get to orbit more reliably and more cheaply (through agencies like NASA, or maybe DARPA) will need to be involved.

But they need to be directed and funded to do the job, and do it with the right goals in mind. The X-33 VentureStar program had the right goals and the right plan for reaching them. (Skylon's goals are similar.) Private industry (Lockheed Martin) was instrumental in helping to define those goals, by the way. The original long range plan for the X-33 program involved a privately operated fleet of launch vehicles, VentureStar. NASA's role was to fund initial risk reduction (technology development) in the X-33 program, and probably subsidize the initial construction of the vehicle fleet at some level (through guaranteed purchases of payload delivery).

X-33 Venture Star (discussion archive in which X-33 engineers participated)
X-33 Venture Star (more archived discussion)

A smart approach would be to fund development of both Skylon (about 12.5 tons to LEO) and X-33/VentureStar (about 25 tons to LEO). The systems are designed to fit different parts of the launch market. They should be developed jointly, so they can use common subsystems, such as compatible payload support for example. The combined systems would begin to create a private launch market, with a much more flexible delivery of payload to space.

Actually, it would be the water going *into* a jet boat that would have to be an oxidizer.

My point is that every kind of jet engine I know of involves feeding the compressed gas from the intake into the combustion chamber. This may be done by the pressure of forward motion (a ramjet or scramjet), or by a turbine, but the compression stage is in-line with the combustion stage.

The design of Sabre evolved from liquid-air cycle engines (LACE) which have a single rocket combustion chamber with associated pumps, preburner and nozzle which are utilised in both modes. LACE engines employ the cooling capacity of the cryogenic liquid hydrogen fuel to liquefy incoming air prior to pumping. Unfortunately, this type of cycle necessitates very high fuel flow.

These faults are avoided in the Sabre engine, which only cools down the air to the vapour boundary and avoids liquefaction. This allows the use of a relatively conventional turbocompressor and avoids the requirement for an air condenser.

The Sabre engine is essentially a closed cycle rocket engine with an additional precooled turbo-compressor to provide a high pressure air supply to the combustion chamber. This allows operation from zero forward speed on the runway and up to Mach 5.5 in air breathing mode during ascent. As the air density falls with altitude the engine eventually switches to a pure rocket propelling Skylon to orbital velocity (around Mach 25).

The SABRE engine has a rocket engine's combustion chamber using cryogenic fuel. Compare the diagrams on http://www.reactionengines.co.uk/sabre.html with any jet engine. Yes, it's got an air intake, but what happens to that air once it enters the engine is completely different.

2) Fuel: Unlike Saturn or Proton rockets, this is a spaceplane. So the fuel tank cannot be meters long and meters wide. it must be compact like a gasoline tank, yet be able to contain ALL fuel for launch from high-altitudes and return.

Excuse me? Why can't the fuel tank be meters long and meters wide? Looking at the design, it appears the fuel tanks are 6m wide and tens of meters long. Indeed they don't appear significantly different from rocket fuel tanks.

Yes. Seriously. Behold the Skylon
and its distant descendant, the Firefly class spacecraft.
Joss, you clever boy.
-S

Sure, except the funding isn't comming from the UK, it's coming from the ESA. The ESA does have a solid history of completing expensive and difficult projects (the ATV comes to mind). As mentioned in the press release, labs in Germany will also be helping Reaction Engines with testing and development.

The Noble rocket car project is a lot of fun, and good inspiration for future engineers, but this new engine technology (not a scramjet BTW) has the potential to completly revolutionise space travel.

Why not take a look at: http://www.reactionengines.co.uk/sabre.html which may answer some of these questions?

Because it was slashdotted. :)

I do understand your objection, but it would appear that the engine designers themselves are referring to this as an air breathing rocket engine on their site.

Sure they've put a slash in that's been lost somewhere, but I don't think it's entirely unreasonable to name this apparently new kind of hybrid engine as an "air breathing rocket engine", as it would seem to have characteristics described by both sets of adjectives.

Yes it's something of an oxymoron, but there are far more depressing examples of abuse of the English language out there.

Why not take a look at: http://www.reactionengines.co.uk/sabre.html which may answer some of these questions? I went to a talk by John Scott-Scott of Reaction Engines a few years back and was very impressed by his description of the engineering work for the Sabre engine. The Reaction Engines guys are practical engineers with a wealth of experience, far from the "bumbling Brits" some other comments suggest.

The funding is primarily intended to enable them to build and test some of the more novel parts of their sabre engine. For example the pre-cooler design which is necessary to cool the air prior to its use as fuel will be tested in front of a jet engine.

From the press release - http://www.reactionengines.co.uk/pr_19_feb_09.html

"The demonstration programme will look at three key areas in the engine.

The first area, conducted by REL, concerns the revolutionary precooler that cools the incoming air as it enters the engine. During the programme a test precooler will be constructed using the actual module design for the flight engines. This will be tested on the companyâ(TM)s B9 jet engine experimental facility at Culham in Oxfordshire.

The second area is the cooling of the combustion chamber, where the propellants are mixed and burnt producing water vapour at around 3,000oC. The SABRE engine uses the air or liquid oxygen as the cooling fluid â" a key and unusual design feature as most rocket engines use the hydrogen fuel for cooling instead. EADS Astrium and DLR in Germany will be conducting this work using demonstration chambers fired at the DLR Lampoldhausen facility.

The third area, led by the University of Bristol, will explore advanced exhaust nozzles that can adapt to the ambient atmospheric pressure. This follows on from the successful STERN (Static Test of ED Rocket Nozzle) test rocket programme that was conducted last year. As part of the ESA contract a new water cooled chamber will be constructed and test fired."

You're correct, it's not much money for a space plane but it's a good step forward in establishing the viability of the engines.

>"...the Sabre rocket engine will be able to take the Skylon with 12 tonnes of cargo..."

That should read "two Sabre rocket engines will be able to take a Skylon with 12 tonnes of cargo..."

That is 13.225 US Short Tons...or approximately 6 tons per engine, if the illustration is any indication.

NASA solved the radiation issue 2 years ago guy. They found out putting foam in the craft walls stops it. Radiation hitting metal sides causes a transmission of the radiation. Foam does not do that. NASA may look ignorant because they want people thinking they're ignorant. Especially enemies they don't want to realize this new craft is a souped-up V2 rocket => http://www.reactionengines.co.uk/skylon_vehicle.html

If you look closely and read the construction specs on this reaction engine vehicle you will read where they put foam in the walls. hahahaha They're making the vehicle now with a heavy engine and heavy fuel, but when they get a true Physics-based engine that does not use fuel those fuel compartments shielded by foam can hold people, animals, plants for transport to the Moon and Mars. Don't be fooled friend. NASA is planning ahead.

Skylon will be able to repay its development costs, meet its servicing and operating costs and make profits for its operators whilst being an order of magnitude cheaper to customers than current space transportation systems.

Can I trust my payload and/or investment dollars to a company that uses "whilst" on their site?

A friend of mine works on the heat exchange system for the SABRE engines that will power Skylon. The SABRE engines are air breathing i.e. they use air they pick up on the way as fuel, hence they need less fuel at launch.

From their website: "The Sabre engine is essentially a closed cycle rocket engine with an additional precooled turbo-compressor to provide a high pressure air supply to the combustion chamber. This allows operation from zero forward speed on the runway and up to Mach 5.5 in air breathing mode during ascent. As the air density falls with altitude the engine eventually switches to a pure rocket propelling Skylon to orbital velocity (around Mach 25)."

More info here: http://www.reactionengines.co.uk/sabre.html

The engine saves weight by using the same combustion chamber during both modes of operation and in air breathing mode it only cools the oxygen to it's vapour point (as opposed to full liquidization) which greatly simplifies the engine design.

At least that's my understanding, IANARS.

From http://www.reactionengines.co.uk/skylon_dev.html :

The total development program will cost about $10 billion.

Also... http://www.reactionengines.co.uk/skylon_vehicle.html

Skylon Statistics

Length: 82m
Fuselage Diameter: 6.25m
Wingspan: 25m
Unladen Mass: 41,000kg
Fuel Mass: 220,000kg
Maximum Payload Mass: 12,000kg

At the start of the take-off roll the vehicle weighs 275 tonnes, whilst maximum landing weight is 55 tonnes.
At take-off the vehicle carries approximately 66 tonnes of liquid hydrogen and approximately 150 tonnes of liquid oxygen for the ascent.
.
.
.
Payload Capabilities

The Sklyon payload bay is 4.6m diameter and 12.3m long. It has been designed to be compatible with expendable launcher payloads but in addition to accept standard aero transport containers which are 8 foot square in cross section and 10, 20, 30 or 40 feet long.
It is anticipated that cargo containerisation will be an important step forward in space transport operations, enabling the "clean" payload bay to be dispensed with.

The vehicle can deliver 12 tonnes to a 300km equatorial orbit, 10.5 tonnes to a 460km equatorial spacestation or 9.5 tonnes to a 460km x 28.5 deg spacestation when operating from an equatorial site.

You do the per flight math.

From http://www.reactionengines.co.uk/skylon_dev.html :

The total development program will cost about $10 billion.

Also... http://www.reactionengines.co.uk/skylon_vehicle.html

Skylon Statistics

Length: 82m
Fuselage Diameter: 6.25m
Wingspan: 25m
Unladen Mass: 41,000kg
Fuel Mass: 220,000kg
Maximum Payload Mass: 12,000kg

At the start of the take-off roll the vehicle weighs 275 tonnes, whilst maximum landing weight is 55 tonnes.
At take-off the vehicle carries approximately 66 tonnes of liquid hydrogen and approximately 150 tonnes of liquid oxygen for the ascent.
.
.
.
Payload Capabilities

The Sklyon payload bay is 4.6m diameter and 12.3m long. It has been designed to be compatible with expendable launcher payloads but in addition to accept standard aero transport containers which are 8 foot square in cross section and 10, 20, 30 or 40 feet long.
It is anticipated that cargo containerisation will be an important step forward in space transport operations, enabling the "clean" payload bay to be dispensed with.

The vehicle can deliver 12 tonnes to a 300km equatorial orbit, 10.5 tonnes to a 460km equatorial spacestation or 9.5 tonnes to a 460km x 28.5 deg spacestation when operating from an equatorial site.

You do the per flight math.

Actually I see more of an SR-71 Blackbird with a fat tail. Can really see it here from above.

Nuclear engines in atmosphere? Not likely!

They just want to go to Sydney, not the moon.

Nuclear engines in atmosphere? Not likely!

They just want to go to Sydney, not the moon.

They'd be using Hydrogen as a fuel, which when burning is about as "green" as they come. Hydrogen generation aside (can use solar, hydroelectric, etc for green generation) you don't have to worry about eco impacts on it like you do with the fuel-guzzlin' Concorde. You could reduce the drag by pushing the thing up to near space altitudes, 100k+ feet altitudes or even higher.

that being said, to do a nonstop flight from sydney to london at that kind of speeds would require a new paradigm in aircraft design to be efficient and cost effective. My hunch is its certainly possible, but I'll do a "wait and see" til they do their ignaugural flight.

A friend of mine is working on the engines for a single stage to orbit vehicle. It's an interesting project although a long way from becoming operational.

I'll second that. Bigger, dumber rockets are emphatically NOT a solution to the orbit problem: the waste of engineering and resources is, frankly, disturbing.

Better solutions have been suggested, but as yet no-one with any serious clout is willing to develop them. The Skylon project is currently trying to gather support from a consortium of aerospace companies, after being 'considered' by ESA.

There appear to be ways of getting to orbit that don't involve carrying things up there only to throw them down again, but no-one is listening. Bit of a shame, really.

Well, there's always Skylon. The technology seems to be basically there; it's mostly just R&D needed. And money, lots and lots of money ($10 billion- not too bad as space goes actually).

Skylon may be an exception:

Basically it uses a precooled jet engine/rocket engine. They believe it would achieve 10:1 thrust:weight and roughly 2000-3000 seconds upto mach 5.

The difficult bit is the precooler, but they've done lab tests on one they built and it doesn't ice, and does work (although they mention unspecified 'manufacturing difficulties' which probably means you can't actually build one big enough or something).

I don't know- it looks promising. $10 billion though.

Although ramjets have been around for decades, they've generally been used at speeds of around Mach 1-3. The BOMARC webpage gives a good example, with a speed of just under 2000 mph. Scramjets might one day be developed to work well at around Mach 5-10, but it's been a tricky problem for engineers to solve.

Scramjet combustion is tricky because the fast air flow can easily blow out the flame. Imagine blowing gently on a small match flame to increase the flame versus blowing strongly on a candle flame to put it out.

Also the shape of the scramjet generally favours a "sweet-spot" in air pressure (altitude) and speed. This makes them OK for cruise missiles, but not so good for orbital launch rockets. You can try variable geometry (change the shape of the inlet/nozzle) but that means some machinery, which adds weight to the system.

That brings me onto another problem - thrust/weight ratio. Rocket engines get much higher thrust/weight ratios than air breathing engines. The best air-breathing thrust-weight design that I've seen is Skylon's SABRE (not a ramjet) which will be nice if they can ever build it.

According to page 161 in SpaceFlight the liquid condensate problem has been solved, and they've successfully run the heat exchanger in a condensing atmosphere for 8 minutes (it only takes 4 minutes to leave the atmosphere).