Author Topic: The Reaction Engines Skylon Master Thread (6)  (Read 88132 times)

Online Chris Bergin

Sixth thread for Reaction Engines/Skylon.

Previous: The Reaction Engines Skylon Master Thread (5)
https://forum.nasaspaceflight.com/index.php?topic=36826.0

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Offline oddbodd

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Re: The Reaction Engines Skylon Master Thread (6)
« Reply #1 on: 08/03/2016 12:31 AM »
Quote from: high road
Quote from: john smith 19
Quote from: high road
dedicated landing strips,
Wrong again. A dedicated launch runway to orbit, but in air breathing only mode Skylon can take off from a much wider range of runways. Most of the length is to meet emergency stop criteria for the fully loaded vehicle, which only apply when it's fully loaded to go to orbit. Landing is much easier with a low empty weight and no engine noise issues.
That's what I said. The Skylon needs a dedicated runway to get to orbit. Using the SABRE engine for an airplane doesn't require the Skylon design.

Apologies for being a pedant, but you said dedicated landing strips initially. As designed Skylon only needs a dedicated runway for full load take off to orbit. On descent from orbit (or inter-airport/spaceport transfer) a standard runway would be usable because the vehicle would be much, much lighter and would not need the additional length. For empty landing pretty much any common major airport runway would suffice. For take off for inter-airport/spaceport there might be some questions about the hot exhaust from the SABRE engines. However because the vehicle would be much lighter I think the expectation is that the engines would not be on full thrust, so the exhaust would not cause damage. Again this is not expected to be a common occurrence, just in the event that the Skylon cannot reach home base for some reason.

Also, even if you meant dedicated orbital launch runway, can you really count that against Skylon? It's not like I can launch an orbital rocket from any old local runway either. Sure the orbital launch runway doesn't exist yet, and will cost a lot to make, but nor did Cape Canaveral exist until it was needed, and I'm pretty sure it cost a lot to build too.

As an illustration of how easily many airports could temporarily host a Skylon, the Antonov has a max take-off load of 640 T (metric), and that has taken off and landed all over the place. The heaviest landing was 285 T (dry-mass) + 247 T (payload) + some fuel reserve, so over 530 T.

For comparison the dry-mass of an empty Skylon is projected to be around 55 T, potentially with a <20 T payload, if transporting something down from orbit for landing. If taking off for inter-airport/spaceport transfer then hydrogen fuel (max of 66 T) would be needed, but no oxidizer (150 T).  It's not clear how much fuel would be needed to self ferry at a sub-sonic speed, but probably a lot less than 66 T. All meaning that Skylon would not need a dedicated takeoff runway in this worst case non-orbital scenario. Just leaving out the heavy oxidizer means the engines can be throttled back significantly. In fact the fully laden take off mass of a Skylon not going to orbit would be around 140-150 T. That's about 2/3 the mass of an empty, un-fueled Boeing 747-8F- the freight/cargo plane.

The only real question mark I can think of is whether the design can get the nose up enough for many runways, as Skylon has a shallow ascent profile in air-breathing mode and I believe the design does not have a lot of control surfaces. Perhaps without the oxydizer and a reduced hydrogen load, the limited control surfaces and trimming the fuel in the front and rear tanks will be enough for a more aggressive angle, and once up at altitude trim it back to neutral.

Obligatory: https://xkcd.com/386/

Offline high road

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Re: The Reaction Engines Skylon Master Thread (6)
« Reply #2 on: 08/03/2016 06:28 AM »

Yes, I did say landing strip. My language doesn't make a difference between the two, so I mistakingly used the literal translation.

This was a reaction to the post that the Skylon is a pretty common design. It's not. That doesn't mean it's impossible, but it's not ordinary. There's quite a lot of new stuff that needs to be built and/or tested for the first time.

But, as I've said before, I'm trying to avoid this continuous exchange of opinions, at least until the SABRE is finished and there's something concrete to talk about.

Offline john smith 19

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Re: The Reaction Engines Skylon Master Thread (6)
« Reply #3 on: 08/03/2016 08:33 AM »
For take off for inter-airport/spaceport there might be some questions about the hot exhaust from the SABRE engines.
Noise is more likely to be the issue. A Skylon on full thrust is equivalent to about the thrust of 2 1/8 Airbus 380's. Due to the higher velocity exhaust that's likely to an underestimate. OTOH without O2 on board that's about 150-160 tonnes lighter.
Quote
However because the vehicle would be much lighter I think the expectation is that the engines would not be on full thrust, so the exhaust would not cause damage. Again this is not expected to be a common occurrence, just in the event that the Skylon cannot reach home base for some reason.
Depends. It does allow the Skylon to be kept at a home country airport then flown down to an equatorial for the flight to orbit.
Quote
Also, even if you meant dedicated orbital launch runway, can you really count that against Skylon? It's not like I can launch an orbital rocket from any old local runway either.
It was noted that a Skylon wheel loading is around that of the old B36. The USAF still has 4 runways that were rated for this aircraft and IIRC it also visited RAF Mildenhall, although I'm not sure if that runway was cleared for the full take off weight.  Obviously due to their inclination they would not allow a full payload to orbit, noise is still likely to be an issue (even being military runways) and getting permission on what are (AFAIK) still active SAC bases would be tricky. But it's not exactly cutting edge technology.
« Last Edit: 08/03/2016 08:35 AM by john smith 19 »
"Solids are a branch of fireworks, not rocketry. :-) :-) ", Henry Spencer 1/28/11  Averse to bold? You must be in marketing."It's all in the sequencing" K. Mattingly.  STS-Keeping most of the stakeholders happy most of the time.

Offline Ravenger

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Re: The Reaction Engines Skylon Master Thread (6)
« Reply #4 on: 08/03/2016 09:21 AM »
Without fuel Skylon will be light enough to be towed by another aircraft. As an alternative to self-ferry it has advantages (mainly saving on engine wear and tear).  So that's another option if Skylon lands at a standard airstrip and needs to be transported back to the launch site.

I'm not sure what type of towing aircraft would be required, and it remains to be seen how practical this would be. It'd be a pretty impressive sight given the size of the spaceplane. The largest glider ever built was the Me 321 Gigant, and that was 'only' 28m long, compared to Skylon's proposed 83m length.


Offline Hankelow8

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Re: The Reaction Engines Skylon Master Thread (6)
« Reply #5 on: 08/03/2016 09:42 AM »
At a recent talk by Richard Varvill for the BIS Space Conference at Charterhouse, he showed a drawing of a Sabre
ground test engine with a single exhaust chamber not the normal 4 chamber combination .

He stated they expect to have the engine running by 2019, he also showed what appeared to be a single engine test  flight model similar to the BAE Systems recent video.

In chat at the conference it seems  Sabre 4 will have a moveable inner high altitude thrust chamber.

When asked what the single engine flight vehicle will cost to build and fly he said around 1 billion, when asked where the money is for this, he just shrugged his shoulders !!

Offline MarekCyzio

Re: The Reaction Engines Skylon Master Thread (6)
« Reply #6 on: 08/03/2016 10:39 AM »
Without fuel Skylon will be light enough to be towed by another aircraft. As an alternative to self-ferry it has advantages (mainly saving on engine wear and tear).  So that's another option if Skylon lands at a standard airstrip and needs to be transported back to the launch site.

I'm not sure what type of towing aircraft would be required, and it remains to be seen how practical this would be. It'd be a pretty impressive sight given the size of the spaceplane. The largest glider ever built was the Me 321 Gigant, and that was 'only' 28m long, compared to Skylon's proposed 83m length.

I seriously doubt this could be possible. Not because of Skylon weight, but because of take off speed and necessary rotation angle.

Offline Ravenger

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Re: The Reaction Engines Skylon Master Thread (6)
« Reply #7 on: 08/03/2016 01:26 PM »
I seriously doubt this could be possible. Not because of Skylon weight, but because of take off speed and necessary rotation angle.

I agree it sounds improbable - but it was Alan Bond himself who suggested it when I asked him about self-ferrying at a Sabre / Skylon talk.

Offline oddbodd

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Re: The Reaction Engines Skylon Master Thread (6)
« Reply #8 on: 08/03/2016 06:30 PM »
Without fuel Skylon will be light enough to be towed by another aircraft. As an alternative to self-ferry it has advantages (mainly saving on engine wear and tear).  So that's another option if Skylon lands at a standard airstrip and needs to be transported back to the launch site.

I'm not sure what type of towing aircraft would be required, and it remains to be seen how practical this would be. It'd be a pretty impressive sight given the size of the spaceplane. The largest glider ever built was the Me 321 Gigant, and that was 'only' 28m long, compared to Skylon's proposed 83m length.



Gotta love those crazy Germans in WW2. Coming up with all kinds of crazy stuff. With the Me 321 Gigant having a max take-off mass of ~34 T, then it seems that the mass itself wouldn't be an issue with modern power/materials/engineering. I just wonder how much reinforcement the two vehicles structures would need to handle the stresses at the towing points from take-off and in-flight turbulence. Modern freight planes (Boeing 747-8F) can dead-lift much greater mass (max cargo of 140 T), and Skylon being a winged lifting body would lift itself, although with a penalty of course for the extra drag the cargo plane has to overcome.

Just the idea makes my head spin a little though :-) I'm not someone who goes to airshows or nerds out at the end of runways, but I think even I'd have to go see a 747-8F take off towing a Skylon. Then I'd chase the thing to watch the Skylon take-off under it's own power :-)

I seriously doubt this could be possible. Not because of Skylon weight, but because of take off speed and necessary rotation angle.

I'm not an aeronautical engineer, so please excuse the question(s)/statement(s) if they're dumb - I'm just going off of instinct on these. Can you explain a bit why you think TOS and RA are an issue? If I have a cargo plane (the aforementioned mentioned 747-8F) dragging an empty Skylon into the air (only ~55 T) then it is going up regardless... it may be damaged, but it'll go up. The wings on the Skylon are intended to get ~300 T into the air, and although I'm not sure how high the TOS is at 300 T, surely the TOS at 55 T is a lot less and would be OK with a cargo planes lower TOS.

I also don't get why RA is an issue. As the Skylon is empty, then again the front canards that provide some small rotational authority will have a much bigger effect due to low mass, plus you have the cargo plane physically pulling the cable upwards a little as it takes off. You'd just need to make sure not to rotate too fast, catching the Skylon tail on the runway. Once Skylon clears the ground, it's just down to how much power the cargo plane engines can deliver as to how steeply you can climb. Which is a lot. Don't forget that Skylon has a very steep climb angle in the rocket phase of an orbital launch, so it shouldn't have any trouble with a steep angle in tow mode instead of an orbital shallow take-off angle.

Offline john smith 19

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Re: The Reaction Engines Skylon Master Thread (6)
« Reply #9 on: 08/04/2016 12:17 AM »
He stated they expect to have the engine running by 2019, he also showed what appeared to be a single engine test  flight model similar to the BAE Systems recent video.
This is the obvious way to turn a single flight weight test engine into a flight vehicle but the configuration has some real problems. The lack of a fuselage makes LH2 storage tough even with the reduced LH2 consumption of the SABRE 4 cycle, and of course it's aerodynamics will be quite different to the Skylon configuration.

On the upside it can give solid flight confidence of the inlet design. Ideally this would be over the full airbreathing range. Going a bit beyond that, to full inlet closure and the transition to full rocket mode would retire a lot of the outstanding concerns about the SABRE cycle, since we know it would operate as a rocket engine from then to orbit.
Quote
When asked what the single engine flight vehicle will cost to build and fly he said around 1 billion, when asked where the money is for this, he just shrugged his shoulders !!
Which you may interpret as "I have no idea" or "I know exactly where it's coming from, but I'm not going to say."

Finance has always been the issue with SABRESkylon. I believe the key is to find a way to turn customer interest into a binding "pre-agreement," with no money up front but an absolute commitment to purchase at a set price (adjusted to track inflation) if the finished product meets certain stated criteria. The results of these negotiations would have to be in a form that can be transferred to the consortium that will make the Skylons to fulfill

With a batch of these in the bank REL would be in a much stronger position to encourage the formation of such a consortium and the consortium would be in a much stronger position to raise finance, since in principle they have already been sold.

The nearest thing I'm aware of to this is in large construction projects, where sub contractors are "novated" from the design team to construction team, but it would be quite a tricky piece of both international contract law and finance to make work.  :(
"Solids are a branch of fireworks, not rocketry. :-) :-) ", Henry Spencer 1/28/11  Averse to bold? You must be in marketing."It's all in the sequencing" K. Mattingly.  STS-Keeping most of the stakeholders happy most of the time.

Online CameronD

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Re: The Reaction Engines Skylon Master Thread (6)
« Reply #10 on: 08/04/2016 04:57 AM »
Finance has always been the issue with SABRESkylon. I believe the key is to find a way to turn customer interest into a binding "pre-agreement," with no money up front but an absolute commitment to purchase at a set price (adjusted to track inflation) if the finished product meets certain stated criteria. The results of these negotiations would have to be in a form that can be transferred to the consortium that will make the Skylons to fulfill

With a batch of these in the bank REL would be in a much stronger position to encourage the formation of such a consortium and the consortium would be in a much stronger position to raise finance, since in principle they have already been sold.

The nearest thing I'm aware of to this is in large construction projects, where sub contractors are "novated" from the design team to construction team, but it would be quite a tricky piece of both international contract law and finance to make work.  :(

At least with a novated construction contract for, say, a high-rise building you know you're going to get a high-rise building at the end of the day: with SABRESkylon you could get nothing.

As I see it, the issue with SABRE/Skylon is that they have yet to demonstrate their technology works.  Perhaps one day they will.. but until then no-one should be surprised by the lack of commercial interest.
With sufficient thrust, pigs fly just fine - however, this is not necessarily a good idea. It is hard to be sure where they are
going to land, and it could be dangerous sitting under them as they fly overhead.

Online Dalhousie

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Re: The Reaction Engines Skylon Master Thread (6)
« Reply #11 on: 08/04/2016 05:08 AM »

As I see it, the issue with SABRE/Skylon is that they have yet to demonstrate their technology works.  Perhaps one day they will.. but until then no-one should be surprised by the lack of commercial interest.

REL have demonstrated quite a bit of the technology works at the bench top level - the pre cooler, inlets, the nozzles under both cold and hot flow conditions.
"There is nobody who is a bigger fan of sending robots to Mars than me... But I believe firmly that the best, the most comprehensive, the most successful exploration will be done by humans" Steve Squyres

Online CameronD

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Re: The Reaction Engines Skylon Master Thread (6)
« Reply #12 on: 08/04/2016 05:22 AM »

As I see it, the issue with SABRE/Skylon is that they have yet to demonstrate their technology works.  Perhaps one day they will.. but until then no-one should be surprised by the lack of commercial interest.

REL have demonstrated quite a bit of the technology works at the bench top level - the pre cooler, inlets, the nozzles under both cold and hot flow conditions.

That's nice... so when will they be testing a complete engine??  ::)

(Note: I'm not even asking for a real, flying Skylon, noooo that would be too much.  Nor even a fully-functioning flight article.. no,  how's about a single test engine strapped to a single test aircraft?  Is that too much to ask?? )
« Last Edit: 08/04/2016 05:26 AM by CameronD »
With sufficient thrust, pigs fly just fine - however, this is not necessarily a good idea. It is hard to be sure where they are
going to land, and it could be dangerous sitting under them as they fly overhead.

Offline john smith 19

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Re: The Reaction Engines Skylon Master Thread (6)
« Reply #13 on: 08/04/2016 08:45 AM »

That's nice... so when will they be testing a complete engine??  ::)
On the assumption you're not trolling and simply don't follow this subject closely they expect to do a full engine test in 2019-2020, as always subject to full funding.
Quote
(Note: I'm not even asking for a real, flying Skylon, noooo that would be too much.  Nor even a fully-functioning flight article.. no,  how's about a single test engine strapped to a single test aircraft?  Is that too much to ask?? )
I'll guarantee it'll be before anyone builds anything with a SCramjet that does anything useful beyond demonstrate you can build an SCramjet whose thrust exceeds its drag.  :)
« Last Edit: 08/04/2016 03:35 PM by john smith 19 »
"Solids are a branch of fireworks, not rocketry. :-) :-) ", Henry Spencer 1/28/11  Averse to bold? You must be in marketing."It's all in the sequencing" K. Mattingly.  STS-Keeping most of the stakeholders happy most of the time.

Offline Jim Davis

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Re: The Reaction Engines Skylon Master Thread (6)
« Reply #14 on: 08/04/2016 12:50 PM »

Quote
(Note: I'm not even asking for a real, flying Skylon, noooo that would be too much.  Nor even a fully-functioning flight article.. no,  how's about a single test engine strapped to a single test aircraft?  Is that too much to ask?? )
I'll guarantee it'll be before anyone builds anything with a SCramjet that does anything useful beyond demonstrate you can build an SCramjet whose thrust exceeds its drag.  :)

You're damning Skylon/SABRE with faint praise. :)

Offline john smith 19

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Re: The Reaction Engines Skylon Master Thread (6)
« Reply #15 on: 08/04/2016 03:42 PM »

Quote
(Note: I'm not even asking for a real, flying Skylon, noooo that would be too much.  Nor even a fully-functioning flight article.. no,  how's about a single test engine strapped to a single test aircraft?  Is that too much to ask?? )
I'll guarantee it'll be before anyone builds anything with a SCramjet that does anything useful beyond demonstrate you can build an SCramjet whose thrust exceeds its drag.  :)

You're damning Skylon/SABRE with faint praise. :)
Well I should admit that SCramjets have probably generated more hypersonics PhD's than deeply pre cooled turbo rockets, much the way fusion research has lead the world in producing plasma physics PhD's.

In fact I expect REL (funding willing) will produce a flight vehicle before other more highly advertized concepts become anything more than clever looking Powerpoints. Never mind leaving the ground.
"Solids are a branch of fireworks, not rocketry. :-) :-) ", Henry Spencer 1/28/11  Averse to bold? You must be in marketing."It's all in the sequencing" K. Mattingly.  STS-Keeping most of the stakeholders happy most of the time.

Offline Rocket Science

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Re: The Reaction Engines Skylon Master Thread (6)
« Reply #16 on: 08/04/2016 04:04 PM »
I'm just looking forward to an all-up engine test within the mentioned time frame, hopefully sooner.
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Offline Lars-J

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Re: The Reaction Engines Skylon Master Thread (6)
« Reply #17 on: 08/04/2016 07:42 PM »
Finance has always been the issue with SABRESkylon. I believe the key is to find a way to turn customer interest into a binding "pre-agreement," with no money up front but an absolute commitment to purchase at a set price (adjusted to track inflation) if the finished product meets certain stated criteria. The results of these negotiations would have to be in a form that can be transferred to the consortium that will make the Skylons to fulfill

With a batch of these in the bank REL would be in a much stronger position to encourage the formation of such a consortium and the consortium would be in a much stronger position to raise finance, since in principle they have already been sold.

The nearest thing I'm aware of to this is in large construction projects, where sub contractors are "novated" from the design team to construction team, but it would be quite a tricky piece of both international contract law and finance to make work.  :(

I sympathize with your frustration, because it is such an a**-backwards business plan. (if accurate) If they have any interest in bringing Skylon to reality, REL needs to LEAD this consortium, not hope that someone else will do it. They need to become the prime contractor.

Offline ChrisWilson68

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Re: The Reaction Engines Skylon Master Thread (6)
« Reply #18 on: 08/04/2016 08:32 PM »
Finance has always been the issue with SABRESkylon. I believe the key is to find a way to turn customer interest into a binding "pre-agreement," with no money up front but an absolute commitment to purchase at a set price (adjusted to track inflation) if the finished product meets certain stated criteria. The results of these negotiations would have to be in a form that can be transferred to the consortium that will make the Skylons to fulfill

With a batch of these in the bank REL would be in a much stronger position to encourage the formation of such a consortium and the consortium would be in a much stronger position to raise finance, since in principle they have already been sold.

I've never seen any evidence at all of any potential customer with the financial resources to matter having any interest in such a "pre-agreement".

And, even if they did by some miracle get those pre-agreements in place, that doesn't automatically mean they'd get development funding because the pre-agreements only address market risk, not development risk.  If I go around and get 100 people to agree to buy my anti-gravity device if it works, that doesn't mean I'll get funding because there's still the substantial risk that I can't actually make an anti-gravity device to fulful the terms of the pre-agreements.

Offline ChrisWilson68

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Re: The Reaction Engines Skylon Master Thread (6)
« Reply #19 on: 08/04/2016 08:42 PM »
Is it possible to have a polite discussion about how SpaceX and Blue Origin affect Reaction Engines without it going off-course into a shouting match about whether SpaceX can't or didn't choose to build a reusable second stage?  I hope so, because I think it's an important issue for Reaction Engines.

The original value proposition of Skylon was versus the old state-of-the-art: expensive, expendable launch vehicles.  Now, the state of the art is changing.  As both Blue Origin and SpaceX move closer to inexpensive, reusable launch vehicles, it erodes the value proposition of Skylon in comparison.  It's one thing to say they want to spend $16 billion to produce a system that reduces launch costs from $250 million per launch to $5 million per launch.  It's a harder sell if the reduction is from $60 million to $5 million.  And even harder when the reduction is from $40 million, then $20 million, and so on.

On the other hand, having other competitors moving toward a low-cost launch system could prove and expand the market, giving investors confidence to invest in REL, particularly if Europe is afraid of the new low-cost launchers and wants its own alternative.

So, which is the bigger effect?  My opinion is that the changes in the market from Blue Origin and SpaceX will have much more of a negative effect on REL than a positive effect.

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