Author Topic: The Reaction Engines Skylon Master Thread (1)  (Read 791176 times)

Offline alexterrell

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Re: The Reaction Engines Skylon Master Thread
« Reply #1500 on: 11/29/2012 08:57 am »


Anyways,
a.  who would be operating the Skylons servicing the ISS
b.  ISS servicing is only a stepping stone for Musk.  He wants to go further than LEO in bigger pieces than 15 tons.
c.  The ISS will be near its end by the time Skylon is on the market.
d.  What says Skylon will not go the way of HOTOL, Space Shuttle, Concorde or SR-71?

Having a good understanding of what answers are possible to all of these questions, is part of Mr Musk's job.

To date, I've only seen Musk as being good at his job. I would expect him to paying attention to Ariane 6, future Long March developments, and Skylon.

He doesn't need to do anything about Skylon now, and not for at least another 5 years.

Offline alexterrell

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Re: The Reaction Engines Skylon Master Thread
« Reply #1501 on: 11/29/2012 09:06 am »
One of the major drawbacks to the SSME was the fact that it had to be disassembled and examined after every flight.

I have not found any reference to these kinds of problems/solutions on the REL website. This could be a show-stopper for the reusability of the SABRE engine.

That was the early SSME.  They haven't had to rebuild the engines after every flight for a long time.  In fact IIRC the Block III (that was planned to come online in 2005 before Columbia changed everything) didn't need to be so much as removed from the orbiter for ~10 flights.  It also had a radically decreased probability of catastrophic failure compared with the Block II.

Also, the difficulties tend to scale very steeply with main chamber pressure, and SABRE uses a significantly lower chamber pressure than the SSME (about half, I believe).
I assume the early block SSME's were based around 1970s technology.

Isn't crack growth now prevented by having a turbine balde grown from a single crystal, complete with ventilation channels. Part of the improvment in commerical engines such as the Trent is that they now operate at a higher temperature than the melting point of the fan.

I would assume that only Rolls Royce, GE and Pratt and Whitney have really mastered this technology.

Offline Rocket Science

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Re: The Reaction Engines Skylon Master Thread
« Reply #1502 on: 11/29/2012 09:19 am »
Exotic engines aside my concern with Skylon is one of directional stability. All hypersonic vehicles had a lager vertical stabilizer ala X-15 to Shuttle. Skylon looks like an X-3 redo with all its inherent problems. I guess we’ll see the final configuration....

http://www.456fis.org/DOUGLAS_X-3.htm

One important difference is that while the X-3 had fuselage-mounted engines, Skylon has them on the wingtips which should give a bit more stability.

Skylon should really be counted as a 'hypersonic' vehicle as it doesn't get into hypersonic flight & stay there, it merely passes through that part of the speed range as it accelerates (out of the atmosphere) up to orbital velocity.
I believe I did say “hypersonic” and still exo-atmospheric flight will require RCS then as well. Transonic regions pose different problems... The engine pods should help and I agree with you on that...
"The laws of physics are unforgiving"
~Rob: Physics instructor, Aviator

Offline Rocket Science

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Re: The Reaction Engines Skylon Master Thread
« Reply #1503 on: 11/29/2012 09:20 am »
The thing is full of liquid hydrogen, and it has a very light structure.  The control surfaces do indeed look too small if you're used to kerosene-fueled vehicles, but these are not "artist's impressions"; they represent the results of actual analysis.
Agreed, it is a light structure being composites but the weight savings are smaller than we sometimes think. You have to lay-up a thick section to equal the strength of some of the alloys and honeycomb used in past aerospace vehicles using a monocoque fuselage.
 
As far as the vertical stabilizer goes I have no information on high mach wind tunnel tests and if anyone has some to share I would be eager to see it. As we both know several “thoughtful” designs ended up making a big hole in the ground. I really wish the project well; it is always interesting to see a new approach to an old problem...
"The laws of physics are unforgiving"
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Offline Crispy

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Re: The Reaction Engines Skylon Master Thread
« Reply #1504 on: 11/29/2012 11:10 am »
It's not a monocoque fuselage. It's a spaceframe, supporting a non-structural skin and internal non-structural tanks. It's more similar to a Zeppelin than an aeroplane or rocket.

Offline Jim

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Re: The Reaction Engines Skylon Master Thread
« Reply #1505 on: 11/29/2012 11:11 am »

One important difference is that while the X-3 had fuselage-mounted engines, Skylon has them on the wingtips which should give a bit more stability.


It is the exact opposite.  Then there are engine out considerations.

Offline Jim

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Re: The Reaction Engines Skylon Master Thread
« Reply #1506 on: 11/29/2012 11:14 am »

Actually, if SABRE works as planned, governments may decree that it replace conventional fossil fuel engines on airliners in order to cut down on CO2 emissions. In that case it would make a profit by government decree. There seems to be a high likelihood of this happening considering the deteriorating state of the environment. It's a straightforward fix for the pollution from airliners.

Wrong.  Hydrogen production is done through hydrocarbon cracking.

Offline tlesinsk

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Re: The Reaction Engines Skylon Master Thread
« Reply #1507 on: 11/29/2012 11:23 am »
Isn't crack growth now prevented by having a turbine balde grown from a single crystal, complete with ventilation channels. Part of the improvment in commerical engines such as the Trent is that they now operate at a higher temperature than the melting point of the fan.

I would assume that only Rolls Royce, GE and Pratt and Whitney have really mastered this technology.

Snecma too:

http://www.snecma.com/-m88-.html?lang=en

(owner of SEP, maker of Ariane 5's Vulcain engines). Probably others.

That raises the question of who will be RE's elusive partners in manufacturing the engines and the spacecraft. If you eliminate US companies for ITAR reasons, it doesn't leave *that* many options. Has RR been involved in space propulsion recently ?

Offline Rugoz

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Re: The Reaction Engines Skylon Master Thread
« Reply #1508 on: 11/29/2012 11:41 am »
Quote
$20m also conveniently enables complete payback on the $2bn investment in only 100 missions or half the airframe's life, opening the window for the Skylon operator to make profit.

If you sell your flights at 40m that is, otherwise it will only cover operating costs.

I think RE plan to produce a vehicle for only 190m, so they make a big plus is they sell at 2bn. Which they have to.

Quote
That raises the question of who will be RE's elusive partners in manufacturing the engines and the spacecraft. If you eliminate US companies for ITAR reasons, it doesn't leave *that* many options. Has RR been involved in space propulsion recently ?

Well RR designed the original HOTOL engine. They have a history of cooperating with snecma, so they may get some help from there (and Astrium, Avio).

Is ITAR so restrictive? I mean there is cooperation between american and european companies in aerospace...
« Last Edit: 11/29/2012 11:41 am by Rugoz »

Offline Crispy

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Re: The Reaction Engines Skylon Master Thread
« Reply #1509 on: 11/29/2012 11:48 am »
Has RR been involved in space propulsion recently ?
Their last major involvement was actually in the HOTOL project, so they should have some experience. Although that may make things difficult, what with the HOTOL technology being a state secret.

Offline Rugoz

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Re: The Reaction Engines Skylon Master Thread
« Reply #1510 on: 11/29/2012 12:13 pm »
^

I thought the technology being state secret worthy are the heat exchangers, and REL intends to manufacture them themselves.

Offline Rocket Science

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Re: The Reaction Engines Skylon Master Thread
« Reply #1511 on: 11/29/2012 01:28 pm »

One important difference is that while the X-3 had fuselage-mounted engines, Skylon has them on the wingtips which should give a bit more stability.


It is the exact opposite.  Then there are engine out considerations.
Jim is of course correct in this vein.  In the event of an “unstart” with the engines sitting so far from the center of gravity you would have a massive asymmetrical thrust and yaw. See our experience with the SR-71 with engines closer inboard...

http://www.barthworks.com/aviation/sr71breakup.htm

"The laws of physics are unforgiving"
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Offline Turbomotive

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Re: The Reaction Engines Skylon Master Thread
« Reply #1512 on: 11/29/2012 01:43 pm »

If you sell your flights at 40m that is, otherwise it will only cover operating costs.

I think RE plan to produce a vehicle for only 190m, so they make a big plus is they sell at 2bn. Which they have to.

Good point. Let's split the difference at $30m, on the assumption that the REL figure of $10m covers the operating costs for a launch? this gives a cost/kg to LEO of $2,000. Still cheaper than Falcon Heavy...

Quote

Is ITAR so restrictive? I mean there is cooperation between american and european companies in aerospace...


Mark Hempsell, on this thread, has categorically ruled out US involvement in Skylon due to ITAR considerations. As I understand it, once a US company's tech is involved, Skylon's potential sales will be restricted by ITAR.




"Men might as well project a voyage to the Moon as attempt to employ steam navigation against the stormy North Atlantic Ocean." - Dionysius Lardner, 1838

Offline Rocket Science

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Re: The Reaction Engines Skylon Master Thread
« Reply #1513 on: 11/29/2012 01:45 pm »
It's not a monocoque fuselage. It's a spaceframe, supporting a non-structural skin and internal non-structural tanks. It's more similar to a Zeppelin than an aeroplane or rocket.
I would appreciate a link for that if you have one handy...
"The laws of physics are unforgiving"
~Rob: Physics instructor, Aviator

Offline Crispy

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Re: The Reaction Engines Skylon Master Thread
« Reply #1514 on: 11/29/2012 03:19 pm »
It's not a monocoque fuselage. It's a spaceframe, supporting a non-structural skin and internal non-structural tanks. It's more similar to a Zeppelin than an aeroplane or rocket.
I would appreciate a link for that if you have one handy...
"Application of Carbon Fibre Truss Technology to the Fuselage Structure of the SKYLON Spaceplane"
Richard Varvill and Alan Bond, 2004
http://www.reactionengines.co.uk/tech_docs/JBIS_v57_x-x.pdf

I'm sure the design has moved on quite a bit in 8 years though!

Offline e of pi

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Re: The Reaction Engines Skylon Master Thread
« Reply #1515 on: 11/29/2012 03:33 pm »
It's not a monocoque fuselage. It's a spaceframe, supporting a non-structural skin and internal non-structural tanks. It's more similar to a Zeppelin than an aeroplane or rocket.
I would appreciate a link for that if you have one handy...
Not a technical report like Crispy's link, but there's this off their site:

Quote
Material Construction

SKYLON's fuselage and wing load bearing structure is made from carbon fibre reinforced plastic and consists of stringers, frames, ribs and spars built as warren girder structures. The aluminium propellant tankage is suspended within this, free to move under thermal and pressurisation displacements.

The external shell (the aeroshell) is made from a fibre reinforced ceramic and carries only aerodynamic pressure loads which are transmitted to the fuselage structure through flexible suspension points. This shell is thin (0.5mm) and corrugated for stiffness. It is free to move under thermal expansion especially during the latter stages of the aerodynamic ascent and re-entry.

Text from here on the Reaction Engines site.

Offline Elmar Moelzer

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Re: The Reaction Engines Skylon Master Thread
« Reply #1516 on: 11/29/2012 03:43 pm »
Quote
In the event of an “unstart” with the engines sitting so far from the center of gravity you would have a massive asymmetrical thrust and yaw.
I would assume that these engines are able to deep throttle like jet engines. So they would probably start them throttled down all the way. But I admit that I may be way off the mark there.

Offline Jim

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Re: The Reaction Engines Skylon Master Thread
« Reply #1517 on: 11/29/2012 03:48 pm »
Quote
In the event of an “unstart” with the engines sitting so far from the center of gravity you would have a massive asymmetrical thrust and yaw.
I would assume that these engines are able to deep throttle like jet engines. So they would probably start them throttled down all the way. But I admit that I may be way off the mark there.

Unstart is an inlet issue and not related to starting the engine

Offline Elmar Moelzer

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Re: The Reaction Engines Skylon Master Thread
« Reply #1518 on: 11/29/2012 03:53 pm »
Quote
Unstart is an inlet issue and not related to starting the engine
Learned something new today :)

Offline Crispy

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Re: The Reaction Engines Skylon Master Thread
« Reply #1519 on: 11/29/2012 04:04 pm »
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?

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