Author Topic: The Reaction Engines Skylon Master Thread (5)  (Read 441252 times)

Offline adrianwyard

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Re: The Reaction Engines Skylon Master Thread (5)
« Reply #200 on: 04/09/2015 03:21 PM »

If you reread my posts you'll see they go like this (with positive fanboi vibe now added in):

1] "Hey fellow-Skylon fans, I just realized that Skylon's re-entry will push the state of the art further forward than anything before it. How come no-one ever mentions that? More than any spacecraft before it, Skylon actually 'flies' in on the canards. How cool. Passively stable re-entry vehicles are for wimps. :-)"
Perhaps because no spaceplane before it had cannards? The importance of trim was one of the big discoveries of the HOTOL project. Putting the engines on the wing tips is a big change. Skylon is designed to avoid the continuous "fluttering" of control surfaces the Shuttle used to keep it stable. You're assuming it will be unstable. That's not a given.

Rather than repeat myself here, I'll refer interested parties (if there are any) back to my initial post on this subject: http://forum.nasaspaceflight.com/index.php?topic=36826.msg1354087#msg1354087.

If you've read anything that indicates the Skylon shape will be more passively stable than the Shuttle during belly-first entry, I'd be very interested in that reference. As you know, the Shuttle was not stable, and its orientation needed to be active maintained with the body flap and elevons.

EDIT: Perhaps we can agree that placing the engines on the wings makes Skylon more symmetrical than the Shuttle in terms of entry (pre-aerodynamic, ~45 degree nose-up) configuration, which is an advantage. But where the orbiter was a simple, relatively compact double-delta, Skylon is a complex shape, and spindly, meaning ISTM that it will have more pronounced forces at the nose and tail that need to be dealt with.

Quote
An interesting question is could it be stable enough to allow a human pilot to fly it without a computer in the loop to stabilize it.

That would make it a very exciting prospect for some potential customers.

Quote

2] "Wouldn't it be awesome if Skylon could take-off and land at regular airports? I know our friends at REL have already worked out how to make it take off in the shortest distance, but I'm just such a fan that I can't help but think about ways to improve Skylon. So, how about adding canards at the back to aid in earlier rotation. Probably a silly idea, I know."
Then you're missing the biggest issue of all. The huge noise level. It's not just the thrust it's the exhaust velocity for air/H2 is much higher than air/kerosene mixture. While OK for occasional takeoffs or emergency landings (which will be unpowered) it's most unlikley there will be fully fueled take offs from any regular airport.

Right. The cases mentioned in my (non fanboi) post were 1] initial delivery to Korou, and 2] recovery after abort: http://forum.nasaspaceflight.com/index.php?topic=36826.msg1355300#msg1355300. I 'worry' that self-ferry even in these rare, special cases might not be possible. And noise is certainly a factor.
« Last Edit: 04/09/2015 04:24 PM by adrianwyard »

Offline adrianwyard

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Re: The Reaction Engines Skylon Master Thread (5)
« Reply #201 on: 04/09/2015 05:01 PM »
And here's the sort of response I was hoping for:

Response to my initial post:

Quote
"While adding redundant control surfaces (e.g. horizontal stabilizers on the tail) would indeed mean you'd still have those available if the front canards were to fail, wouldn't the failed/stuck surfaces cause you control problems that your remaining surfaces might not be able to overcome?"

Me:

"You're probably right. Better to put extra effort into making sure the canards always work. (And are sized for self-ferry in addition to orbital take-off)."
« Last Edit: 04/09/2015 05:09 PM by adrianwyard »

Offline john smith 19

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Re: The Reaction Engines Skylon Master Thread (5)
« Reply #202 on: 04/10/2015 07:43 AM »
Rather than repeat myself here, I'll refer interested parties (if there are any) back to my initial post on this
If you've read anything that indicates the Skylon shape will be more passively stable than the Shuttle during belly-first entry, I'd be very interested in that reference. As you know, the Shuttle was not stable, and its orientation needed to be active maintained with the body flap and elevons.
I cannot cite a reference. Considering the Shuttles design you had a series of big "point masses" (3 SSMEs, their plumbing and the OMS modules, along with the APUs, their fuel and cooling) in the tail. That puts a big  weight in the tail and you're trying to the Shuttle at 70 degs without flipping it over.

Skylons, engines, and returning payload (if any) are with the wings in the middle. This means that rather than fighting a big (point) tail mass (  you have a relatively light fuselage in 2 parts which are (roughly) the same mass. That means surfaces can be smaller and response times less critical.

BTW the slab sides on the orbiter made for a very bad glider which was very prone to cross winds.
Quote
EDIT: Perhaps we can agree that placing the engines on the wings makes Skylon more symmetrical than the Shuttle in terms of entry (pre-aerodynamic, ~45 degree nose-up) configuration, which is an advantage. But where the orbiter was a simple, relatively compact double-delta, Skylon is a complex shape, and spindly, meaning ISTM that it will have more pronounced forces at the nose and tail that need to be dealt with.
It's not aesthetics, it's putting the biggest masses on or near the longways  centre of mass so they have near zero moment  :( That's important because the centre of pressure is constantly shifting during reentry as you go from M23 to M0.

There was nothing simple about Shuttles shape. Shuttle histories state it took 40-50 000 hrs of wind tunnel time to develop. Part of that was for the cross range requirements of the USAF and I would suspect partly trying to adapt the blunt body aerodynamics developed for war head reentry capsules into a useable form for a winged vehicle, which basically junked the usual rule of thumb for high speed aircraft that thinner wings are always better.
Quote
Right. The cases mentioned in my (non fanboi) post were 1] initial delivery to Korou, and 2] recovery after abort: http://forum.nasaspaceflight.com/index.php?topic=36826.msg1355300#msg1355300. I 'worry' that self-ferry even in these rare, special cases might not be possible. And noise is certainly a factor.
In 1 the vehicle will be less than 50% of its GTOW to orbit. There is every reason to think it's takeoff run will be much shorter. Keep in mind 1.5Km of that 5.5Km is solely for emergency stopping of a fully loaded Skylon. I don't know if you could drop the takeoff run and emergency braking distance to 3.5Km but I think it would be close.

2)is more a case of planning for an emergency and the legal issues around them. Clearing airspace for a Skylon on abort then getting it down. Which runway it comes down on would depend on how much is pre programmed into its auto pilot and to what extent it can receive external commands. Getting it back to Kourou would then involve a damage assessment, possible repairs up to engine replacement and refueling with LH2. While different in detail from a conventional aircraft the process would be pretty much the same.

"You're probably right. Better to put extra effort into making sure the canards always work. (And are sized for self-ferry in addition to orbital take-off)."
I guess that's a nice illustration of why it's difficult to do "tone" on the internet.  :(

Can you explain why you think the control surfaces which are sized to control a fully loaded Skylon won't be able to cope with the loads imposed by a vehicle that's 150 tonnes lighter in self ferry and over 200 tonnes lighter during re entry? That seems illogical.
"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 lkm

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Re: The Reaction Engines Skylon Master Thread (5)
« Reply #203 on: 04/10/2015 11:31 AM »
Hempsell has already stated on the thread that any ordinary sub-3km runway can launch a self-ferry Skylon.

http://forum.nasaspaceflight.com/index.php?topic=24621.msg987883#msg987883


Also as a reminder there are two lectures coming up this month for those able to attend, on Tuesday 14th with Richard Varvill:

http://aerosociety.com/Events/Event-List/1934/Skylon-and-Sabre-Bringing-Space-Down-to-Earth

and on Wednesday 22nd with Alan Bond:

http://aerosociety.com/Events/Event-List/1686/The-Sabre-Engine


Offline adrianwyard

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Re: The Reaction Engines Skylon Master Thread (5)
« Reply #204 on: 04/10/2015 07:36 PM »
I'm confident everybody in this conversation is within 10% agreement, so to go on would say more about the hazards of forum-based communication than anything else.

For example, lkm says "Hempsell has already stated on the thread that any ordinary sub-3km runway can launch a self-ferry Skylon". Which should settle the issue, right? But in the cited comment Hempsell actually says the following - in 2012 - "we currently believe believe Skylon would be able to use sub-3 km runways".

I take that to mean it's not a 100% done deal, and so a topic for conversation. But when I raise the topic of self-ferry, and speculate on the usefulness of greater control authority if it turns out to be marginal on shorter runways JohnSmith19 asks me: "why you think the control surfaces which are sized to control a fully loaded Skylon won't be able to cope with the loads imposed by a vehicle that's 150 tonnes lighter in self ferry and over 200 tonnes lighter during re entry? That seems illogical."

Just because I'm interested in the self-ferry case doesn't mean I think it can't be done (and REL are liars). But by the same token, REL said they currently believe it can be done, which means there's a chance it might be tricky. That's what makes me raising the issue legit, rather than 'illogical'.

Same thing with Skylon entry. Just because I note that it's rarely talked about - and will not be a walk in the park - doesn't mean that I think it's impossible. But neither do I think it's established that no further work is necessary.

___

To conclude: I don't think anyone here is saying that self-ferry and entry 1] require no further design and testing, or 2] will clearly fail as designed. If you are, then let's continue, otherwise let's change the subject.
« Last Edit: 04/10/2015 07:56 PM by adrianwyard »

Offline lkm

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Re: The Reaction Engines Skylon Master Thread (5)
« Reply #205 on: 04/10/2015 09:11 PM »
I'm confident everybody in this conversation is within 10% agreement, so to go on would say more about the hazards of forum-based communication than anything else.

For example, lkm says "Hempsell has already stated on the thread that any ordinary sub-3km runway can launch a self-ferry Skylon". Which should settle the issue, right? But in the cited comment Hempsell actually says the following - in 2012 - "we currently believe believe Skylon would be able to use sub-3 km runways".

I take that to mean it's not a 100% done deal, and so a topic for conversation. But when I raise the topic of self-ferry, and speculate on the usefulness of greater control authority if it turns out to be marginal on shorter runways JohnSmith19 asks me: "why you think the control surfaces which are sized to control a fully loaded Skylon won't be able to cope with the loads imposed by a vehicle that's 150 tonnes lighter in self ferry and over 200 tonnes lighter during re entry? That seems illogical."

Just because I'm interested in the self-ferry case doesn't mean I think it can't be done (and REL are liars). But by the same token, REL said they currently believe it can be done, which means there's a chance it might be tricky. That's what makes me raising the issue legit, rather than 'illogical'.

Same thing with Skylon entry. Just because I note that it's rarely talked about - and will not be a walk in the park - doesn't mean that I think it's impossible. But neither do I think it's established that no further work is necessary.

___

To conclude: I don't think anyone here is saying that self-ferry and entry 1] require no further design and testing, or 2] will clearly fail as designed. If you are, then let's continue, otherwise let's change the subject.

My intention was only to point out that Hempsell had talked about it previously in the thread as it was some time ago and five threads back and I thought it might add to the debate, not end it. My thought on shortening take off requirements was whether optionally payload could be traded for increased take off thrust by augmenting with LOX.

On reentry, obviously nothing about that is easy but Skylon has always struck me as a somewhat prettier version of Faget's DC-3 and as such presumably has a similar reentry profile.

Offline john smith 19

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Re: The Reaction Engines Skylon Master Thread (5)
« Reply #206 on: 04/14/2015 08:34 PM »
To conclude: I don't think anyone here is saying that self-ferry and entry 1] require no further design and testing, or 2] will clearly fail as designed. If you are, then let's continue, otherwise let's change the subject.
Certainly.
"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 Mutley

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Re: The Reaction Engines Skylon Master Thread (5)
« Reply #207 on: 04/15/2015 07:50 AM »
Lots more jobs appearing on the Reaction Engines website

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

Offline francesco nicoli

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Re: The Reaction Engines Skylon Master Thread (5)
« Reply #208 on: 04/15/2015 08:01 AM »
nice! are these new jobs or sobstitutions of people that left?

anyway, SpaceX is so close now. The others cannot afford to to ignore reusability any more. Although I am seriously afraid someone at ESA will fall into the Siren's trap of a "REUSABLE ARIANE 6 BY 202X"........


Offline john smith 19

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Re: The Reaction Engines Skylon Master Thread (5)
« Reply #209 on: 04/15/2015 08:31 AM »
Lots more jobs appearing on the Reaction Engines website

http://www.reactionengines.co.uk/careers.html
Yes that's quite a broad range. Note some of them only make sense in the context of a company expecting to grow quite a lot and to a quite substantial size.

nice! are these new jobs or sobstitutions of people that left?

anyway, SpaceX is so close now. The others cannot afford to to ignore reusability any more. Although I am seriously afraid someone at ESA will fall into the Siren's trap of a "REUSABLE ARIANE 6 BY 202X"........
A lot of those roles look new.

"REUSABLE ARIANE 6 BY 202X"........

Hmm.  :( The fact ULA are committing to something may be more relevant. Before SX could be dismissed as just a private company who could do whatever they liked based on the whim of their CEO.

I think REL are still very weary of being a "government" programme (especially if that's an EU) so they have to steer a very tricky course.

SABRE/Skylon remains very high risk relative to the sort of systems Ariane 6 is being described as, although quite what that final shape will be seems to be changing. Are "all solids" still the baseline?

What might be possible would for ESA to say they need a European backup plan funded at some level in case commercial customers remain implacably opposed to an all solid design.

Solids BTW generate much more vibration on the payload and large ones are difficult (impossible?) to shut down.

"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 francesco nicoli

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Re: The Reaction Engines Skylon Master Thread (5)
« Reply #210 on: 04/15/2015 08:53 AM »
I still wonder whether the UK government, or REL themselves, sent an application for funding at the Commission for the new Juncker fund. This is not public ownership in the classical way... If they didn't, I would at least like to undestand why :)

Offline john smith 19

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Re: The Reaction Engines Skylon Master Thread (5)
« Reply #211 on: 04/15/2015 12:35 PM »
I still wonder whether the UK government, or REL themselves, sent an application for funding at the Commission for the new Juncker fund. This is not public ownership in the classical way... If they didn't, I would at least like to undestand why :)
Interesting question but from my (very) cursory look at the plan it's target is to stimulate the growth of businesses in Southern Europe, such as Spain and Greece, Italy perhaps.

One of its goals does seem to be increasing investment in higher risk transport infrastructure projects, and Skylon could definitely be described as one of those.  :)

Sadly it seems Britain may be a bit far North for this option to be viable.   :(
"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 francesco nicoli

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Re: The Reaction Engines Skylon Master Thread (5)
« Reply #212 on: 04/15/2015 01:45 PM »
well, why it is correct that the goal is stimulating investment, the fund will not have a geographic orientation. true, it constitutes an incredible opportunity for southern Europe, but it has been repeatedly stated that projects will be selected solely on the basis of their benefits- even in EU countries which do not financially participate in the fund (even tough financially contributing to the fund allows countries to have a board member and so influencing decisions, which is not bad if you want to get some of the money you put in back into your country). Then again, the fund is done for industrial development..so maybe REL can apply in a few years or so!

Offline Mutley

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Re: The Reaction Engines Skylon Master Thread (5)
« Reply #213 on: 04/15/2015 03:02 PM »
http://www.reactionengines.co.uk/press_release.html

New press release from Reaction Engines

Looks like the USAF agrees with ESA with regards the feasability of the SABRE concept

Offline Star One

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The Reaction Engines Skylon Master Thread (5)
« Reply #214 on: 04/15/2015 03:10 PM »
http://www.reactionengines.co.uk/press_release.html

New press release from Reaction Engines

Looks like the USAF agrees with ESA with regards the feasability of the SABRE concept

Hopefully an announcement that may lead to more significant developments. Probably not in the direction of Skylon as I can't see the USAF being that interested in that as a concept, but perhaps in other areas of in atmosphere vehicle development.
« Last Edit: 04/15/2015 03:27 PM by Star One »

Offline francesco nicoli

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Re: The Reaction Engines Skylon Master Thread (5)
« Reply #215 on: 04/15/2015 03:45 PM »
"Reaction Engines Ltd. and AFRL are now formulating plans for continued collaboration on the SABRE engine; the proposed work will include investigation of vehicle concepts based on a SABRE derived propulsion system, testing of SABRE engine components and exploration of defence applications for Reaction Engines’ heat exchanger technologies."


very big deals coming. The first listed is (I believe) wha the AFRL is truly interested in- SKYLON might not be suitable for defense purposes, but other "vehicle concepts based on a SABRE derived propulsion system" might surely be.

Offline Jim

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Re: The Reaction Engines Skylon Master Thread (5)
« Reply #216 on: 04/15/2015 03:49 PM »
http://www.reactionengines.co.uk/press_release.html

New press release from Reaction Engines

Looks like the USAF agrees with ESA with regards the feasibility of the SABRE concept

No, feasibility is the wrong word.  AFRL "investigations examined the thermodynamic cycle of the SABRE concept and found no significant barrier to its theoretical viability provided the engine component and integration challenges are met."

They found that it can happen but have not ruled on that it will happen.
« Last Edit: 04/15/2015 03:50 PM by Jim »

Offline Star One

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Re: The Reaction Engines Skylon Master Thread (5)
« Reply #217 on: 04/15/2015 03:53 PM »

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

New press release from Reaction Engines

Looks like the USAF agrees with ESA with regards the feasibility of the SABRE concept

No, feasibility is the wrong word.  AFRL "investigations examined the thermodynamic cycle of the SABRE concept and found no significant barrier to its theoretical viability provided the engine component and integration challenges are met."

They found that it can happen but have not ruled on that it will happen.

But if anyone has the funds to make it happen it's the USAF, they are the kind of customer REL need.

Offline Oli

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Re: The Reaction Engines Skylon Master Thread (5)
« Reply #218 on: 04/15/2015 03:53 PM »
http://www.reactionengines.co.uk/press_release.html

New press release from Reaction Engines

Looks like the USAF agrees with ESA with regards the feasability of the SABRE concept

From the press release:

Quote
"Although application of the SABRE for single stage to orbit space access remains technically very risky as a first application, the SABRE may provide some unique advantages in more manageable two stage to orbit configurations."

Given the huge projected development cost of the SSTO version, I kind of agree with that.

They could, for example, leave the atmosphere at lower speed, in order to reduce aerodynamic pressure, and reenter at Mach 15 or so instead of orbital speed. The vehicle would then land downrange similar to the Hopper concept and could be towed back to Kourou.

An upper stage with Vinci could do the rest. It would probably fit into the vehicle (with a longer bay obviously).

Any other ideas?


« Last Edit: 04/15/2015 03:57 PM by Oli »

Offline Star One

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Re: The Reaction Engines Skylon Master Thread (5)
« Reply #219 on: 04/15/2015 04:07 PM »

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

New press release from Reaction Engines

Looks like the USAF agrees with ESA with regards the feasability of the SABRE concept

From the press release:

Quote
"Although application of the SABRE for single stage to orbit space access remains technically very risky as a first application, the SABRE may provide some unique advantages in more manageable two stage to orbit configurations."

Given the huge projected development cost of the SSTO version, I kind of agree with that.

They could, for example, leave the atmosphere at lower speed, in order to reduce aerodynamic pressure, and reenter at Mach 15 or so instead of orbital speed. The vehicle would then land downrange similar to the Hopper concept and could be towed back to Kourou.

An upper stage with Vinci could do the rest. It would probably fit into the vehicle (with a longer bay obviously).

Any other ideas?

Couldn't they have a smaller parasite hypersonic vehicle for access to orbit carried on the back of a larger slower carrier craft.

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