The Reaction Engines Skylon Master Thread (1)

[alexterrell]

Thanks for that. I guess I'll be staying in on Wednesday.

I think the last sentence is a bit premature.

[Crispy]

Thanks for that. I guess I'll be staying in on Wednesday.

I think the last sentence is a bit premature.

Just an ambiguous sentence IMO (better copy editor needed!)

eg: I have taken a sabbatical from work to build my own house.

Doesn't mean that I have moved into it. Or that ground has even been broken.

And I too know where I will be on Wednesday night

[PMN1]

Thanks for that. I guess I'll be staying in on Wednesday.

I think the last sentence is a bit premature.

Positive vibes...positive vibes......the bridge will be up........

[alexterrell]

And I too know where I will be on Wednesday night

Perhaps we should all meet in a pub and ask the landlord to switch from Sky to BBC4. It'll be just like going to watch the Autumn Internationals

[Crispy]

That was a pretty good programme told the whole story, from hotol to skylon without too much glossing over the technical details, and only a couple of factual errors. Fingers crossed there will be another in 10 years to finish off the story!

[Matt32]

Yup, it was a good summary of the story so far. Didn't really learn anything new about the technical aspects of sabre/skylon, but some poignant comments from Alan Bond about the politics of it- particularly the classification of HOTOL technology stalling development for decades after government funding was withdrawn. Glad things seem to be moving now.

[Crispy]

Also, I never put 2 and 2 together and realised that they're based at the same research park as JET. You can go on (free!) guided (by scientists!) tours of that place, which I *highly* recommend: http://www.ccfe.ac.uk/visits.aspx

[elmarko]

Really good programme, my complaint is that they didn't explain WHY staging was necessary, ie, thrust-to-weight, heavy dead-weight etc. They just basically said "if you launch a normal rocket you have to do it in stages, but this new skylon jobbie doesn't need to do that"

I absolutely love BBC4. I can't believe they're cutting back on it

[ANTIcarrot]

Just watched it. Yet another programme on how 'wings are absolutely needed for rocket engines to work - somehow'. (Funny how technical details can get lost in a show about technology.) Couldn't help but sniggering when they confused NASP and the X-33. Or when they talked about NASA avoiding revolutionary rocket engines, while the screen showed a plug nozzel rocket test. So yeah. Methinks the technical advisors weren't quite on speaking terms with the final editing team.

A lot of model shots were noticably reused. How many times did we see HOTOL turn slowly through 90 degrees? And not a single picture of Dynasoar? (Low budget much?) I know what that is. I'm pretty sure most watching don't. And of course no pictures, model, or mention of the DC-X. Though that was understandable. The 'lone man with an idea' narative loses impact when there are other teams doing exactly the same thing, and the differences between DC-Y and Skylon might have forced the BBC to talk about technical issues, which they tend to hate doing.

Still, it was good to see Reaction Engines getting some good publicity.

[john smith 19]

Just watched it. Yet another programme on how 'wings are absolutely needed for rocket engines to work - somehow'. (Funny how technical details can get lost in a show about technology.) Couldn't help but sniggering when they confused NASP and the X-33. Or when they talked about NASA avoiding revolutionary rocket engines, while the screen showed a plug nozzel rocket test. So yeah. Methinks the technical advisors weren't quite on speaking terms with the final editing team.

I'm not sure what film you saw. I think the point was rather that *reusability* required wings to give *affordable* launch costs.

And not a single picture of Dynasoar?

Hermes, which was both mentioned and *pictured* was essentially the French in 1980 wanting to do what the US has rejected in 1962. That it was turned down pretty much covers the subject.

And of course no pictures, model, or mention of the DC-X. Though that was understandable. The 'lone man with an idea' narative loses impact when there are other teams doing exactly the same thing, and the differences between DC-Y and Skylon might have forced the BBC to talk about technical issues, which they tend to hate doing.

DC-X is a radically different concept to Skylon. The goal might be roughly similar but the approach was very different. Skylon *confronts* the payload mass fraction issue of SSTO head on, DC-X accepted it. I think it was pretty tactful of them not to mention the Shuttles payload being as bad as that of a conventional VTOL SSTO concept, without *any* of the benefits.

You need to consider the context for this film. It was a British made independent documentary (not made by the BBC) primarily for a UK/European audience on a mainly factual non mainstream digital UK channel. By modern standards it covered a *lot* of technical ground in a limited amount of time. The scramjet coverage was more relevant to an HTOL vehicle than the DC-X (DC-Y never got very far) and plug nozzles (including at least 1 *flightweight* LO2/LH2 design) have been in ground test since the early 1960s.

Still, it was good to see Reaction Engines getting some good publicity.

And for many viewers probably the first time they even knew it existed.

[93143]

I think it was pretty tactful of them not to mention the Shuttles payload being as bad as that of a conventional VTOL SSTO concept, without *any* of the benefits.

That's not fair either.  If the Shuttle had to simply dump its payload in the initial insertion orbit and immediately reenter empty, and all the major components were ditched without any opportunity for inspection, you might have a point.  Dirt cheap it wasn't, but it was also neither expendable nor a mere launch vehicle, not by a long shot.

Skylon doesn't quite match Shuttle's capabilities, but it comes a lot closer than any other currently-planned vehicle we know anything about, and it should be far cheaper, safer, and quicker to turn around between flights...

[PMN1]

Interesting program.

I liked the comparison of the modelling techniques used by the aerospace and atomic industries of the time.

[Space OurSoul]

Hi folks,

Long shot, but I don't suppose anybody knows a legal way to watch this in the US? I'm aware of the proxy-plus-iplayer route but I'm too straight to do that

I'm willing to watch it on YouTube before the Beeb pulls it, but i don't see that anyone has posted it yet...

Thanks
-Jeff

[ARD]

Hi folks,

Long shot, but I don't suppose anybody knows a legal way to watch this in the US? I'm aware of the proxy-plus-iplayer route but I'm too straight to do that

I'm willing to watch it on YouTube before the Beeb pulls it, but i don't see that anyone has posted it yet...

Thanks
-Jeff

I hope that posting the Youtube link doesn't violate any NSF rules. 

[Ric Capucho]

Just watched and enjoyed the BBC4 show. All sounds viable enough, and can see how it all hinges on that heat exchanger and also some form of altitude compensating rocket bell... Aerospike?

Anyways, if I was lucky enough to be an eccentric billionaire, then I'd still be looking at some form of proof of concept before I'd be willing to put a few hundred million into this. Perhaps a sounding rocket equivalent?

Ric

[RobLynn]

Just watched and enjoyed the BBC4 show. All sounds viable enough, and can see how it all hinges on that heat exchanger and also some form of altitude compensating rocket bell... Aerospike?

I am pretty sure that the altitude compensating E-D nozzle is nice to have but not essential, they operate at pretty high chamber pressure (15MPa?), and can over-expand to a large degree at sea level because they have such a high thrust to weight ratio and Isp that they can afford to throw some of that away for 2-3 minutes out of the 12 minutes of air-breathing.

Heat exchanger is the really critical part, an incredibly high number of fragile components in it that have to work reliably with large temperature and pressure changes, That would be the big risk item in my book.

They have done fantastic work in coming up with a vehicle configuration that has such low weight - something like 25 tonnes excluding engines but including 1100m³ fuel, landing gear, wings, thrust structure, TPS, payload bay, OMS etc while being stable with or without a payload aboard.  Crude calculations suggest that converting such a vehicle to SSME class rocket propulsion and vertical takeoff might just about work as an SSTO RLV without airbreathing (though with far less versatility and perhaps less safe abort modes).

[HMXHMX]

Just watched and enjoyed the BBC4 show. All sounds viable enough, and can see how it all hinges on that heat exchanger and also some form of altitude compensating rocket bell... Aerospike?

I am pretty sure that the altitude compensating E-D nozzle is nice to have but not essential, they operate at pretty high chamber pressure (15MPa?), and can over-expand to a large degree at sea level because they have such a high thrust to weight ratio and Isp that they can afford to throw some of that away for 2-3 minutes out of the 12 minutes of air-breathing.

Heat exchanger is the really critical part, an incredibly high number of fragile components in it that have to work reliably with large temperature and pressure changes, That would be the big risk item in my book.

They have done fantastic work in coming up with a vehicle configuration that has such low weight - something like 25 tonnes excluding engines but including 1100m³ fuel, landing gear, wings, thrust structure, TPS, payload bay, OMS etc while being stable with or without a payload aboard.  Crude calculations suggest that converting such a vehicle to SSME class rocket propulsion and vertical takeoff might just about work as an SSTO RLV without airbreathing (though with far less versatility and perhaps less safe abort modes).

I haven't been keeping up with the mass and volume details of Skylon, but a point I've made off-and-on for the past few years is that the propellant mass fraction of the vehicle is highly ambitious, and I say this as a long-time advocate of SSTO.  Using the data above, I note that if we replaced the 1100m³ of propellant volume with low-average density LOX-LH2, we're looking at a PMF of 0.94.  If we used LOX-RP1 or equivalent, it approaches 0.98.  In that respect, Skylon is more difficult to build than a pure VTHL SSTO.  The only real advantage which attends the HTHL concept is runway takeoff and marginally increased safety that is hard to quantify, so I question the wisdom of investing in the air-breather technology when it would be far less expensive and risky to go another route, like VTHL or VTOL (or even RASV-style HTHL with sled).

[e of pi]

Reaction Engine's Skylon technical page lists an unladen mass of 41 mT, and a fuel load of 220 mT, with 12 mT payload adding up to basically the cited 273 mT maximum takeoff mass. That's more like 81% fuel at takeoff if you count the payload in with the dry mass, or 85% if you don't.

[RobLynn]

Reaction Engine's Skylon technical page lists an unladen mass of 41 mT, and a fuel load of 220 mT, with 12 mT payload adding up to basically the cited 273 mT maximum takeoff mass. That's more like 81% fuel at takeoff if you count the payload in with the dry mass, or 85% if you don't.

Yes, but tank mass per volume is typically almost identical for LOX or LH2:
http://selenianboondocks.com/wp-content/uploads/2010/02/tankMERs.gif
so it is quite reasonable to compare mass fraction of Skylon converted to typical LOX/LH2 rocket mixture ratio of 6:1, and on that basis it has a very high Mass Ratio as Gary pointed out.

Skylon C1 is something like 220 tonnes of fuel with 950m³ of LH2 and 150m³ of LOX.  If it were all rocket at 6:1 mix with same total volume it would be more like 400 tonnes of fuel, 800m³ LH2 and 300m³ LOX so just 150m³ of LH2 tank would have to be changed to LOX tank.

Using the tank mass kg/m³ figures for the shuttle ET from the above link (and they don't include insulation) Skylon tanks 10560kg, LH2/LOX rocket tanks of same total volume 10690kg.

[FinalFrontier]

Was very impressed by the BBC documentary and I thought it gave a good overview of how things have gone so far.


Will be interesting to see how this concept develops during the next 10 years, if it really does work once its fully integrated (ie the full up engines on a small test bed style vehicle, sort of like SS1) then it will be a game changer.

It still has a long way to go but there was a time when space ship one, falcon and dragon, and the jet aircraft also had "a long way to go" and yet they all became a reality (though ss2 has yet to make an operational flight).

I have some measure of faith in this idea, I guess you could say, but I would very much be interested to see if, once it worked, how much you could scale it up. The initial vehicle can't do all that much in terms of Mass to Leo, but if it could be scaled it would have major implications.