The Reaction Engines Skylon Master Thread (1)

[simonbp]

You're correct as far as you go. What you're leaving out is that the temperature of the air that the precooler will have to deal with is strongly dependent on the efficiency of the inlet. Inlet design has to tested in a wind tunnel and in flight to insure the design specification is met. Even in this age of computational fluid dynamics there is a great deal of uncertainty in inlet design at high Mach numbers, both in pressure recovery and installed weight.

Which precisely why they are planning on building two rocket-powered "Nacelle Test Vehicles" to test/verify their inlet design. They should start flying around the time SABRE begins ground tests.

[Robotbeat]

The engine isn't a super/hypersonic combustion device, which means you can test everything downstream of the inlet on the ground relatively easily. You don't need a hypersonic wind tunnel, if that's what you're implying. The inlet will take the flow down below transonic (Mach 0.5 is pretty typical for most airbreathers). All you'd have to do is provide heated air at subsonic velocity, which is a much easier proposition. Yes, maybe you're not "completely" testing it then, but building a subscale just to test the inlet is a waste of money.

You're correct as far as you go. What you're leaving out is that the temperature of the air that the precooler will have to deal with is strongly dependent on the efficiency of the inlet. Inlet design has to tested in a wind tunnel and in flight to insure the design specification is met. Even in this age of computational fluid dynamics there is a great deal of uncertainty in inlet design at high Mach numbers, both in pressure recovery and installed weight.

+1

[bolun]

Europe’s Next-gen Rocket Design Competition Included Surprise Finalist

http://www.spacenews.com/launch/120713-europe-rocket-design-finalist.html

Astrium Space Transportation and OHB AG will lead two consortia to perform a design of a new heavy-lift launch vehicle for the European Space Agency (ESA) following a bidding competition that included a surprise third bidder in Reaction Engines Ltd. of Britain, ESA Director-General Jean-Jacques Dordain said here July 10.

[strangequark]

The engine isn't a super/hypersonic combustion device, which means you can test everything downstream of the inlet on the ground relatively easily. You don't need a hypersonic wind tunnel, if that's what you're implying. The inlet will take the flow down below transonic (Mach 0.5 is pretty typical for most airbreathers). All you'd have to do is provide heated air at subsonic velocity, which is a much easier proposition. Yes, maybe you're not "completely" testing it then, but building a subscale just to test the inlet is a waste of money.

You're correct as far as you go. What you're leaving out is that the temperature of the air that the precooler will have to deal with is strongly dependent on the efficiency of the inlet. Inlet design has to tested in a wind tunnel and in flight to insure the design specification is met. Even in this age of computational fluid dynamics there is a great deal of uncertainty in inlet design at high Mach numbers, both in pressure recovery and installed weight.

Sure, but you wouldn't build a subscale vehicle just to test the inlet, which was my point. Testing the integrated engine, sans inlet, gives you phenomenal opportunity to validate the bulk of the engine design inexpensively (in aerospace terms) on the ground. At that point, given that an inefficient inlet is highly unlikely to result in LOV, it makes sense to move to airbreathing tests on a full scale vehicle. This is dramatically different from a scramjet, where you can't practically get a flightlike environment on the ground, your instrumentation is limited, and you can't recover the vehicle.

[Jim Davis]

...given that an inefficient inlet is highly unlikely to result in LOV...

To be generous, this is highly debatable. If one nacelle suddenly unstarts loss of vehicle is by no means "highly unlikely".

[Seer]

Regarding Skylon's chances, I'd be interested in hearing what people think is more likely to succeed: Skylon or f9r. This is from a purely technical perspective rather than taking funding issues into account.

Give a rating from 1 to 10 for each one.

[peter-b]

Regarding Skylon's chances, I'd be interested in hearing what people think is more likely to succeed: Skylon or f9r. This is from a purely technical perspective rather than taking funding issues into account.

Give a rating from 1 to 10 for each one.

I have an opinion on this, but I'm not going to post it here because this updates thread is not the correct venue.

[Seer]

The internet demands you share your opinion!

[aero]

This question is way off topic. Ask it in general general, maybe.

[Robotbeat]

Regarding Skylon's chances, I'd be interested in hearing what people think is more likely to succeed: Skylon or f9r. This is from a purely technical perspective rather than taking funding issues into account.

Give a rating from 1 to 10 for each one.

This is a master thread, not an update thread, so...
F9r more than Skylon, mostly because:
1) F9R has an order of magnitude less development cost (I know, I know... not supposed to take it into account... but if we assume the same level of funding for both, then F9R comes out way ahead).
2) The technology is basically all demonstrated with F9R. The engines are already tested and work. They have a prototype demonstration vehicle getting ready for first flight within the next couple months. How far away is Skylon's suborbital demo vehicle? At least an order of magnitude further away, probably a good decade! Vehicles the size of Skylon take a very long time to develop. The platform needed for F9R is already flying to orbit now, and soon will be demonstrating several of its key recovery mechanisms (Dragon powered landing is similar in concept to what second-stage recovery may be like).
3) F9R will almost surely debut with partial reusability at first, which is a far more attainable goal (both technically and from a minimum-number-of-annual-flights-to-stay-viable perspective), helping to retire with paid flights a lot of risk for the full vehicle. (and already, the knowledge base for orbital operations is already built for the expendable vehicle).
4) Not only do the engines, etc, needed for F9R already exist, but the TPS has already been used on Dragon successfully.
5) F9R is already getting significant funding from a company able to finish its development... Skylon is still in start-up mode, essentially. They need a huge amount of funding to get to completion. And probably need an aerospace prime to sign on with them.

[Seer]

Thanks for your response Robotbeat, I'll give mine after others have given theirs.

[tnphysics]

I agree with Robotbeat

[krytek]

Regarding Skylon's chances, I'd be interested in hearing what people think is more likely to succeed: Skylon or f9r. This is from a purely technical perspective rather than taking funding issues into account.

Give a rating from 1 to 10 for each one.

SpaceX is a little bit, maybe 1 point, higher on that scale.

[PMN1]

What other areas are the pre-cooler and heat exchanger applicable to?

[krytek]

What other areas are the pre-cooler and heat exchanger applicable to?

I'm guessing anything high end that requires cooling.
Cars, plans, spaceships, electronics, etcetera.

[A_M_Swallow]

Gas refrigeration may be another use.  Buildings if the pre-cooler can do volume rather than high temperature difference.

[aero]

Remember that the precooler uses liquid hydrogen to dump heat. That may limit its usefulness for general applications.

[93143]

It uses helium gas as a working fluid.  The liquid hydrogen is just the obvious readily-available cold side.  There's no reason it needs LH2 as a sink; in fact, the test setup uses liquid nitrogen.

Also, the heat exchangers are currently extremely expensive.  So much so, according to Mark Hempsell, that space launch is about the only application REL has identified that they aren't overkill for.  Here's hoping somebody (either the current manufacturer, or somebody else once the patent runs out) figures out how to make them cheaper without compromising the quality...

This post is not to be interpreted as me re-entering the thread.  I have unfinished business with a couple of posters, but I don't have time to finish it now.  Arguments on the Internet are extremely time-consuming...

[john smith 19]

SpaceX is a little bit, maybe 1 point, higher on that scale.

Nice graphic.  The key point is that It's tempting to think that with multiple F9 launches under their belt adapting it to re-usability is going to be pretty simple as (presumably) most of the hardware will be the same and therefor their TRL is higher than REL's.

But that ignores that a *lot* of the key parts of the REL concept can be ground tested (as they were designed to be) and a lot of the rest have a high level of confidence from other sources (engines off re-entry of a winged vehicle has been tested about 200 times over a 30 year period).

Spacex's approach seems simpler but is more subtle and cannot *realistically* be tested on the ground. How much flight testing has been done (on all Spacex flights) is debatable. AFAIK the only thing that came *close* is the DC-X, which also demonstrated turnaround of a LO2/LH2 fueled vehicle within 26 hours in a design using expendable engines.

Spacex have a well behaved TSTO ELV which seems to be maturing into a good LV and be stretched into a heavy lift vehicle. That puts F9 at TRL9 and F9H not too far behind. The TRL of the reusable elements is less clear.

[Hauerg]

Regarding Skylon's chances, I'd be interested in hearing what people think is more likely to succeed: Skylon or f9r. This is from a purely technical perspective rather than taking funding issues into account.

Give a rating from 1 to 10 for each one.

F9r >> Skylon:
Even if both receive the necessary funding the technology of Skylon is so sensitive to failures that I have a hard time imagining Skylon succeed.
EVERYthing has to work in order to get ANYthing into LEO.
On the other hand e.g. an F9r 1st stage might crashland and explode but still have put payload into orbit, earned money for SpaceX.
Also I feel that Skylon would be hard to scale up.

I would LOVE to see Skylon fly, but:
F9r wins 7:4