The Reaction Engines Skylon Master Thread (1)

[Jim]

Yes Jim, you're entirely right but...

The rocket part of it is, IMHO, not that different from other rockets. My point, and perhaps I haven't made it very well, is that, after accumulating experience with rockets for 50 years (other people, that is, certainly not me), engineers can build a rocket, first on the back of an envelope and then inside a computer and calculate what the thrust figures will be and the model will be sufficiently good that when they build the engine, they'll get the thrust figure they expected to get, plus or minus (probably minus) a certain percentage.

They never get the ISP right.

[QuantumG]

They never get the ISP right.

Yep. I wish Sutton had more on ISP/altitude estimation techniques. It'd stop so much confusion for beginners (which is almost everyone who hasn't read Sutton).

[Hempsell]

They never get the ISP right.

?? if you agree we can predict the thrust of course we can predict the Isp. One determines the other. We have had no problems with Isp modelling in the past.

[STS-200]

In the event of such an inlet failure, could they not transition to internal LOX supply and abort the mission (to whatever suborbital path is possible), or would events be too rapid for valves and flows to react?

Unstart can be a very rapid event (milliseconds), much too fast for the turbomachinery to react. Either the vehicle is strong enough to survive the resultant aero loads or it isn't. While intakes can be quickly re-started, I suspect that a vehicle with such small margins as a space plane would have to abort anyway.

However, Skylon would fly fairly straight and in a gentle climb without any rapid throttling, with all of the high-Mach supersonic flight in the Stratosphere - flight conditions that are quite smooth and predictable. Unstart is much more likely to occur in variable-throttle manoeuvering flight in the more turbulent Troposphere.

[Chris Bergin]

Pretty amazing thread, 200,000 views and very British - that pleases me

At the weekend (or in the coming days) I'll start a fresh thread, especially as we have that milestone of the engine success. So look to find a cut off point in your conversations in preparation for the new thread.

PS Anyone from Reaction on here. Would love to do an article....but I don't like re-writing press releases (boring).

[Turbomotive]

When you've made The Sun and my local paper, the Bangkok Post you know you've arrived!

With some foreboding though, this reminds me of reading about HOTOL in the Daily Express in the 1980s...

[alexterrell]

Pretty amazing thread, 200,000 views and very British - that pleases me

At the weekend (or in the coming days) I'll start a fresh thread, especially as we have that milestone of the engine success. So look to find a cut off point in your conversations in preparation for the new thread.

PS Anyone from Reaction on here. Would love to do an article....but I don't like re-writing press releases (boring).

Now that the engine has passed this critical test, perhaps its no longer an "Advanced Concept". Hopefully in about 5 years it'll have its own section or two like SpaceX. Not sure where it should go now though.

[mr. mark]

Just because it passed a few tests does not mean it's flying. Until that happens it's an advanced concept.

[aero]

However, Skylon would fly fairly straight and in a gentle climb without any rapid throttling, with all of the high-Mach supersonic flight in the Stratosphere - flight conditions that are quite smooth and predictable. Unstart is much more likely to occur in variable-throttle maneuvering flight in the more turbulent Troposphere.

What kind of "variable-throttle maneuvering flight" did the SR-71 do?

The SR-71 was a camera platform, it needed to fly straight and level to do its photographic mission from high altitude. Weather fronts changed air temperature, changed thrust and lift exciting the vehicle longitudinal mode changing angle of attack and camera pointing. We fixed it with dynamic pressure feedback to the throttle control system.

The Skylon will experience the same changes in weather as it accelerates to orbit which may or may not excite vehicle dynamic modes and may or may not be controllable as the Sabre engines will most likely be already at full power. Although Skylon may be able to accelerate through these changes in angle of attack with little or no adverse affect.

[ukrocketman]

Pretty amazing thread, 200,000 views and very British - that pleases me

At the weekend (or in the coming days) I'll start a fresh thread, especially as we have that milestone of the engine success. So look to find a cut off point in your conversations in preparation for the new thread.

PS Anyone from Reaction on here. Would love to do an article....but I don't like re-writing press releases (boring).

3 that I know of, and in the case of Mark Hempsell and Roger Longstaff, pretty senior too.

If they don't read this, I'll annoy them both this weekend about doing something ;-)

[Hempsell]

They never get the ISP right.

?? if you agree we can predict the thrust of course we can predict the Isp. One determines the other. We have had no problems with Isp modelling in the past.

Every other recent engine development says otherwise (RD-180, RS-68, J-2X, etc)

I am surprised - another good reason to buy your rocket engines from Reaction Engines.

[mmeijeri]

What kind of "variable-throttle maneuvering flight" did the SR-71 do?

Outrunning Libyan SAMs?

[Andrew_W]

What kind of "variable-throttle maneuvering flight" did the SR-71 do?

Outrunning Libyan SAMs?

The SR-71's defense was its speed, altitude and small radar CS.

[Citizen Wolf]

I think it's safe to say that Jim won't be investing any money in the next phase of development at REL. 

[65816]

However, Skylon would fly fairly straight and in a gentle climb without any rapid throttling, with all of the high-Mach supersonic flight in the Stratosphere - flight conditions that are quite smooth and predictable. Unstart is much more likely to occur in variable-throttle maneuvering flight in the more turbulent Troposphere.

What kind of "variable-throttle maneuvering flight" did the SR-71 do?

To be fair, SR-71 unstarts were much less frequent once they moved from the pneumatic to digital inlet control. Also, most unstarts were experienced at lower altitudes while maneuvering.

Concorde also had a digital inlet control system and that worked flawlessly.


Is it possible to use this precooler design on a internal combustion engine? Should improve efficiency greatly.

[Jim]

Concorde also had a digital inlet control system and that worked flawlessly.

Not the same.  Mach 2 jets fly all the time.

[65816]

Concorde also had a digital inlet control system and that worked flawlessly.

Not the same.  Mach 2 jets fly all the time.

Name any other jet that cruised at and above(up to M2.2x in tests) M2 without afterburners... AFAIK, only later variants of Tu-144 did. And not as efficiently - it was a poor copy anyway.

Besides, engines could have gone faster. The aluminium body couldn't.

[ukrocketman]

I am surprised - another good reason to buy your rocket engines from Reaction Engines.

That attitude shows that you really don't know what is ahead of you and you mock others in the field who are much more experienced.  You have yet to demonstrate "a" rocket engine much a complex one like SABRE. 

Also, forgot to include the Merlin.

To be fair Jim, the Reaction Engines team are not short of a few clues. In fact Alan Bond, was involved in the Rolls Royce RZ2 engines for Blue Streak when he worked for Val Cleaver, the British equivalent of Von Braun. Mark Hempsell who posts here, has been involved with various programmes for decades, including DC-X. Roger Longstaff who posts here, was involved in HOTOL and X-33 amongst others prior to Skylon.

[grondilu]

Not too surprisingly, Skylon has been Wired:

http://www.wired.com/autopia/2012/11/reaction-engines-hypersonic/

You guys here are highly technical so I'm not sure you're interested in a wired article, but it's such a famous website with a wild audience that I thought it was worth mentionning.

[Turbomotive]

I'm primarily on here for the opportunity to gain wisdom from the Reaction Engines team and I am very grateful they are deigning to communicate on a public forum.

Apart from their individual experience (which is as pointed out above, significant), they are the ones with a real project on their hands, which is now excitingly on the threshold of major funding for significant real world testing of the SABRE concept. There is nothing like SKYLON being developed anywhere else in the world and its possibilities are also exciting, from Jovian colonies to the death of the ELV. I'm here positing deliberately ambitious, and possibly impossible possibilities, but which if possible, are quite intoxicating.

Therefore, it's good to have the wealth of experience on the thread from old hands on the Space Shuttle, SR71 and so on, to be skeptical about the detailed technical and financial challenges of the programme, that I am sure is beneficial to REL as challenges for them to consider, and we all learn.

As good scientists though, and I mean people with a scientific mindset, I hope we'd all expect the proof of the pudding is in the results from the real world. Many of the technical issues floated on this thread, including the overall viabillity of SABRE and SKYLON, will now be answered or confirmed one way or another in the next couple of years by the ground demonstration SABRE. Let's wait for that and see who is right or wrong, over to you REL.

Would finally like to commend REL for a very thoroughly transparent and scientific approach to their technology verification. None of the many independent experts involved have raised serious technical flags to my knowledge. People like Jaques Dordain wouldn't be giving SKYLON airtime if they did not think the concept had technical merit.

The bottom line - Do i think it'll work? Yes, when I see it running - but luckily, this is no longer a purely academic question.