Author Topic: The Reaction Engines Skylon Master Thread (5)  (Read 420279 times)

Offline Nilof

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Re: The Reaction Engines Skylon Master Thread (5)
« Reply #280 on: 05/11/2015 03:38 PM »
In contrast there is limited experience of pumped LH2/LO2 engines anywhere with 4 designs in the US (and the only production design dating from the 1960's) with 2 in Europe and 1 (IIRC) in Russia.


OTOH, looking only at engines that have actually flown on orbital flights or are very likely to do so in the near future, and ignoring hot tests:

US:
RL-10
J-2
SSME
RS-68
BE-3

Russia:
KVD-1
RD-0120 series
RD-0146 series
...and a ton of incredibly crazy experimental engines such as the 30 MPa chamber pressure RD-701 which have to count for something. Though the russians have avoided LH2 stages because of excellent non-cryogenic alternatives.


Europe:
HM-7 series
Vulcain series
Vinci

Japan:
LE-5 series
LE-7 series

India:
CE-7.5

China:
YF 73 and 75 series.

...imho, while LH2 is still a PITA as far as engine development is concerned, it is not necessarily more so than the decision to use a staged combustion cycle. Virtually everyone who has been concerned with improving the performance of their rockets rather than getting something into space period, has developed an LH2 expander or gasgen at some point.
« Last Edit: 05/12/2015 09:13 AM by Nilof »
For a variable Isp spacecraft running at constant power and constant acceleration, the mass ratio is linear in delta-v.   Δv = ve0(MR-1). Or equivalently: Δv = vef PMF. Also, this is energy-optimal for a fixed delta-v and mass ratio.

Offline 93143

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Re: The Reaction Engines Skylon Master Thread (5)
« Reply #281 on: 05/11/2015 09:21 PM »
Expander cycle is good for upper-stage engines.  It has a maximum thrust, and it's not very high.  If you want high T/W and high Isp in a large engine that has to operate at sea level, some form of staged combustion is by far your best bet.

The SABRE seems to dodge a lot of the problems by taking advantage of the helium loop, which would be extra weight and complexity on a pure rocket but is essentially free here because they need it for the airbreathing mode.  This should significantly attenuate the issues with seals and metallurgy.  It's still not simple to develop, but if you add the cost of the SSME to the cost of the GE90 you do blow past REL's estimate...

Oh, wait just a second; that reminds me:

That's $360M to get to first working prototype.

Excuse me; that's £360M.  Everything else I said is fine.
« Last Edit: 05/11/2015 10:11 PM by 93143 »

Offline lkm

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Re: The Reaction Engines Skylon Master Thread (5)
« Reply #282 on: 05/12/2015 10:51 PM »
So it seems Jo Johnson is the new minister for Space ( and some other none spacey stuff) and as such seems likely to be involved in making some of the governments decisions regarding Skylon.
 
http://en.wikipedia.org/wiki/Jo_Johnson

On the one hand this may be seen as a bad thing as the man seemingly has no more than a high school science education  but I posit this may actually be a cunning plan as he has a background in finance as well as fluent French and an MBA from INSEAD. If the government was indeed interested in assisting Reaction Engines in forming a Skylon consortium with Airbus in the next four years that could be just the sort of background you might want in the minister in charge of helping to make it happen.

Offline john smith 19

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Re: The Reaction Engines Skylon Master Thread (5)
« Reply #283 on: 05/13/2015 03:35 PM »

http://en.wikipedia.org/wiki/Jo_Johnson
He is also Boris Johnsons's brother.

Time will tell if this is an asset or a liability.
"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 Seer

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Re: The Reaction Engines Skylon Master Thread (5)
« Reply #284 on: 05/13/2015 07:48 PM »
I notice that Skylon's fuselage is pinched at the middle where the payload bay is. I wonder why they decided not to use a wider payload bay of ~ 6 metres. How much of a payload penalty would that involve.

Offline adrianwyard

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Re: The Reaction Engines Skylon Master Thread (5)
« Reply #285 on: 05/13/2015 08:03 PM »
It's a good guess this pinch is due to Area Rule influencing the design. (http://en.wikipedia.org/wiki/Area_rule)

So if you made the payload bay wider, the rest would widen proportionally too.

Offline RanulfC

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Re: The Reaction Engines Skylon Master Thread (5)
« Reply #286 on: 05/13/2015 08:58 PM »
I notice that Skylon's fuselage is pinched at the middle where the payload bay is. I wonder why they decided not to use a wider payload bay of ~ 6 metres. How much of a payload penalty would that involve.
It's a good guess this pinch is due to Area Rule influencing the design. (http://en.wikipedia.org/wiki/Area_rule)

So if you made the payload bay wider, the rest would widen proportionally too.

Yes, you have to keep in mind that Skylon is more of (but not "an") an aircraft than a standard launch vehicle so flying through the atmosphere to around Mach-5 makes aerodynamics important :)

Randy
From The Amazing Catstronaut on the Black Arrow LV:
British physics, old chap. It's undignified to belch flames and effluvia all over the pad, what. A true gentlemen's orbital conveyance lifts itself into the air unostentatiously, with the minimum of spectacle and a modicum of grace. Not like our American cousins' launch vehicles, eh?

Offline Seer

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Re: The Reaction Engines Skylon Master Thread (5)
« Reply #287 on: 05/13/2015 08:58 PM »
I hadn't heard of that before. Well you learn something every day.

Offline francesco nicoli

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Re: The Reaction Engines Skylon Master Thread (5)
« Reply #288 on: 05/14/2015 08:38 AM »
it would be good to have any kind of company update at this point. How is the work doing?

Offline knowles2

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Re: The Reaction Engines Skylon Master Thread (5)
« Reply #289 on: 05/14/2015 11:44 PM »
it would be good to have any kind of company update at this point. How is the work doing?
This year they have gone crazy with the press updates, okay their been 3, which is three times more than we got in 2014.

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

There were little updates and new pics and graphs and data release by the team at conferences but you will have to hunt them down by reading the threads on this website.

I'm not the only one that hopes when they get to the stage of testing their engine and components of the engine they will get a bit more open with us, perhaps with some nice pictures and videos. They could learn a thing or two about marketing from Space X.

The news section of their site haven't been undated since May 2014.

Offline pmcaerospacefreighter

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Re: The Reaction Engines Skylon Master Thread (5)
« Reply #290 on: 05/18/2015 10:35 PM »
I feel like they get a trickle of funding from the UK Govt, not enough to do anything much with it, but enough for the politicians to feel good about themselves.

Offline john smith 19

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Re: The Reaction Engines Skylon Master Thread (5)
« Reply #291 on: 05/19/2015 12:00 AM »
I feel like they get a trickle of funding from the UK Govt, not enough to do anything much with it, but enough for the politicians to feel good about themselves.
REL are pretty good at making a (relatively) little go a long way.

The UK governments (roughly) $94m (over 2 years) may not sound much  but it's about 1/6 of their needed budget for the work they want to do. REL are extremely wary of any government gaining a controlling interest in the project and being able to dictate design or engineering decisions.

It is enough to allow them to make significant progress on the project.
"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 pmcaerospacefreighter

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Re: The Reaction Engines Skylon Master Thread (5)
« Reply #292 on: 05/22/2015 05:03 PM »
a single rocket launch (I assume they need to test their engines at altitude / hypersonic speed) would eat a lot of that.

Offline Hanelyp

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Re: The Reaction Engines Skylon Master Thread (5)
« Reply #293 on: 05/22/2015 05:28 PM »
Ram jets have been operated with inlet and exhaust nozzles not greatly different from what a sabre engine would need.  Everything in between is not directly exposed to speed and altitude, accepting hot air at one end and producing hotter air at increased pressure at the other end.  A test of the sabre cycle core needs neither high speed not now pressure ambient environment.

Offline john smith 19

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Re: The Reaction Engines Skylon Master Thread (5)
« Reply #294 on: 05/22/2015 06:57 PM »
a single rocket launch (I assume they need to test their engines at altitude / hypersonic speed) would eat a lot of that.
Did no one tell you what happens when you "assume" things?

The pre cooler at the front of the engine decouples the air temperature (cryogenic) and velocity (about M0.5) from the ambient environment (up to 1000c and M5.5)

Pre coolers with this power to weight ratio and ability to do frost control have never been done before, which is why this had to be tested first as a failure would have been game over for the whole project.

What that means is (unlike the SCramjets) you don't need to put it on a rocket to test its performance, although putting it on some kind of test vehicle would be a bonus.

Most of this can be found on the technical documents on the REL website.
"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 93143

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Re: The Reaction Engines Skylon Master Thread (5)
« Reply #295 on: 05/22/2015 07:38 PM »
They're not putting the engine on a test vehicle during this phase of development.  Once it's proven on the test stand (yes, it gets static thrust just fine because it has a turbocompressor), the rest of the ~$5B engine development program can commence, and that might conceivably involve sticking the engine on a test vehicle (which could easily be reusable as it's essentially an airplane).

Now, they have talked about using an internally-developed sounding rocket to test nozzle ideas, but that's not quite the same thing...
« Last Edit: 05/22/2015 08:28 PM by 93143 »

Offline adrianwyard

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Re: The Reaction Engines Skylon Master Thread (5)
« Reply #296 on: 05/23/2015 08:17 PM »
As other have said below much of SABRE can be ground tested, but the nacelle - with its re-entry capable nose cone - is definitely novel, critical, and will need to be proven definitively early in development either through ground testing or in flight. REL had mentioned developing an NTV - a Nacelle Test Vehicle before now, but I donít believe itís in the current plan.

At first blush the nacelle/inlet looks reminiscent of other flown configurations such as that used on the SR-71: itís axisymmetric with a translating shock cone. But the fact that it can close fully and successfully resist re-entry shock/plasma/thermal conditions is new.

I did wonder if one of the purposes of the Valkyrie project was to fly a nacelle model (in closed configuration) into re-entry-like conditions.

It seems to me there are a couple of challenges with the nacelle cone and louvres.

1] The louvres need to be thin to minimize drag during air-breathing (see the attached screen shot) of a REL animation. But this thinness limits the options for thermal protection: thereís no mass/structure to sink heat into, and not much room for active thermal control.

2] The sharp tip of the cone will receive the most severe heating as itíll be close to the shock wave, and has little volume to sink heat back into. There may be room in the cone for active cooling. Or a more drastic departure would be to swap the actual cone for an aerospike, such as that used on the Trident ICBM. (see picture from http://en.wikipedia.org/wiki/Drag-resistant_aerospike below) During atmospheric Ďforwardí flight the spike is extended to form a simulated cone, but for re-entry itís retracted leaving the cone blunt and so better suited to face the airflow (which now comes from below).

An aerospike could also be used to alleviate heating on the sharp fuselage nose as it will face similar heating issues.

(A pre-emptive note to JohnSmith19: Please donít take these comments and suggestions to be my dismissal of the Skylon project as impossible. Thinking through engineering challenges like Skylon is a hobby of mine, and I share my thoughts in hopes of hearing corrections when Iím mistaken.)
« Last Edit: 05/23/2015 11:08 PM by adrianwyard »

Offline john smith 19

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Re: The Reaction Engines Skylon Master Thread (5)
« Reply #297 on: 05/23/2015 10:48 PM »
At first blush the nacelle/inlet looks reminiscent of other flown configurations such that on the SR-71: itís axisymmetric with a translating shock cone. But the fact that it can close fully and successfully resist re-entry shock/plasma/thermal conditions is new.
True.
Quote
1] The louvres need to be thin to minimize drag during air-breathing (see the attached screen shot) of a REL animation. But this thinness limits the options for thermal protection: thereís no mass/structure to sink heat into, and not much room for active thermal control.
Like a lot of things in aeospace design "it depends." Skylon is so big what looks thin as a picture may be very substantial IRL. those louvres may actually be several cms thick.
Quote
2] The sharp tip of the cone will receive the most severe heating as itíll be close to the shock wave, and has little volume to sink heat back into. There may be room in the cone for active cooling. Or a more drastic departure would be to swap the actual cone for an aerospike, such as that used on the Trident ICBM. (see picture from http://en.wikipedia.org/wiki/Drag-resistant_aerospike below) During atmospheric Ďforwardí flight the spike is extended to form a simulated cone, but for re-entry itís retracted leaving the cone blunt and so better suited to face the airflow (which now comes from below).
Strictly Trident use an "aero disk" but the idea is very similar. Artillery shells are probably the main users of actual "aero spike" designs.
Quote
An aerospike could also be used to alleviate heating on the sharp fuselage nose as it will face similar heating issues.

(A pre-emptive note to JohnSmith19: Please donít take these comments and suggestions to be my dismissal of the Skylon project as impossible. Thinking through engineering challenges like Skylon is a hobby of mine, and I share my thoughts in hopes of hearing corrections when Iím mistaken.)
REL have stated that the parts needed to resist peak heating loads they would be using a version of Reinforced Carbon Carbon. This has demonstrated service up to 3000c in the Shuttle nose area, with the right surface coating. DLR is one of REL's partners and they have substantial experience in RCC.

Hopefully glass reinforced silicon carbide will be adequate for the majority of both the fuselage, wings and nacelles, but there are alternatives.
« Last Edit: 05/24/2015 08:52 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 Seer

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Re: The Reaction Engines Skylon Master Thread (5)
« Reply #298 on: 05/24/2015 05:06 PM »
There are a number of new things that need to be developed. These include
1. The transitioning inlet
2. lox cooled chamber
3. heat exchangers, both the primary one and the high temperature silicon carbide one.
4. active thermal protections systems on the canards and winds and perhaps the inlet.
5. an aerodynamic configuration that can fly at hypersonic speeds (mach 5), re-entry and low landing speeds.
6. super lightweight tanks that are 1% of the mass of the propellant.

Having a high number of active systems increases the probability that one of them will fail during flight and also increases the maintenance and inspection burden between flights.

Offline RobLynn

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Re: The Reaction Engines Skylon Master Thread (5)
« Reply #299 on: 05/24/2015 06:12 PM »
There are a number of new things that need to be developed. These include
...
6. super lightweight tanks that are 1% of the mass of the propellant.
...

From memory for C1 configuration about 220Mg LOX+LH2 and ~1000m≥ LH2 and 150m≥ LOX,
http://selenianboondocks.com/2010/02/calculating-propellant-mass-sensitive-term/tankmers/
At very best cryogenic tanks are about 7kg/m≥, so might be as little as 8Mg - say 4-5% of propellant mass.  Not realistic to target 25% of that.
I'm a "glass is twice as big as it needs to be" kinda guy

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