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Skylon Spaceplane

RanulfC

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Thanks. RanulfC, you are correct as far as you go. However, SSTO projects used to be all the rage and they carry far more dead weight into orbit. Any kind of two-stage system is a great advance on them in the terms you describe. The original B.Ae concept when migrating HOTOL to a more realistic two-stage scenario was to use a subsonic mothership for the low-altitude, low-speed bit, where the demands on engine intake geometry vary dramatically from those at high Mach numbers. That really did relieve the Reaction Engines team of some notoriously intractable intake optimisation problems. That they now think it is worth grappling with those problems for the sake of lower orbiter mass is the bit I find interesting.
Interim HOTOL (the one using the An-225) was not Alan Bond team but BAe, after the two went their own, separate ways (REL was funded in 1989).
Of course if Interim HOTOL had actually been advanced then StratoLaunch would have had something to point at they could carry :)

Randy
 

steelpillow

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... as rocket exhaust flares sideways far more than jet exhaust and cooked Skylon's tail section.
While it needed to be better addressed than REL did the answer was beefing up the insulation and adding a heat resistant structure. One of the reasons for having a TSTO instead of an SSTO is that you can adjust the structures of both stages to optimized levels.
Putting permanent re-usable structure in the path of a rocket exhaust has never been done before that I can recall. It is a pretty hairy environment and would need a raft of technological advances to cope with the violent thermal fluctuations, mechanical vibration and reactive chemicals. It's not tame like a re-entry plasma.

Then there are little things like the one-engine-out condition when too high up for the rudder to work.
That's a misson abort, throttle down to minimum of the working engine and heavy use of the RCS till you get low enough for the rudder to be effective and limp to the nearest airfield that can handle the vehicle. It was a risk but keep in mind the vehicle was designed to show off the engines and was a very conservative design given the parameters so it could afford some added structure and weight gain. Most other SSTO's can't.
Easy enough in air when you have a fin to apply a counter-torque. But in space, an engine failure would set the craft spinning faster and faster until the other engine was also cut. You would have to ensure automatic cutoff within a very short space of time and enough manoeuvring thruster authority to counter the maximum spin that might have been applied by then, and with enough reserve to decelerate for re-entry. I am not convinced that the added weight would remain manageable.

If the Space Shuttle can get the CG right with rear-mounted rockets, I don't see why B.Ae can't.
HOTOL had issues because it had two engine systems in a way since the intake and heat-exchanger mass was forward,
That second system forward of the CG just meant adjusting the wing position a little. HOTOL's main problem with the CG was that to keep it from moving aft, a more complicated fuel/oxidant tankage arrangement would have been needed and that would have weighed too much. Now I stop to think more about the Shuttle, it didn't have to balance when fully laden, as it took off vertically, so the fuel and oxidant could go anywhere. Of course nowadays we just ensure the control authority is there and let the silicon worry about the stability, so Skylon could end up highly unstable with an aft CG and still land safely.
 
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Archibald

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Of course nowadays we just ensure the control authority is there and let the silicon worry about the stability, so Skylon could end up highly unstable with an aft CG and still land safely.
Spot on, in a rather hilarious way that made me smile. We are living at a time when algorithms and "silicon" could make a brick fly. Have you see that Iron Man wannabee flying over Les Champs Elysées on July 14th ? the media was astounded, but I wasn't. There was a very similar "flying platform" 70 years ago, in the 50's, but instability killed it, the unfortunate pilot couldn't control the thing. It took 70 years but nowadays, algorithms can tame unstabilty. Also see all the drones and quadcopters: they are extremely ugly and an absolute insult to aerodynamics, yet they fly.


Vive la France, yes, but that is hardly knew - only with fast computing and algorithms to tame the unstability, really.
 

martinbayer

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Thanks. RanulfC, you are correct as far as you go. However, SSTO projects used to be all the rage and they carry far more dead weight into orbit. Any kind of two-stage system is a great advance on them in the terms you describe. The original B.Ae concept when migrating HOTOL to a more realistic two-stage scenario was to use a subsonic mothership for the low-altitude, low-speed bit, where the demands on engine intake geometry vary dramatically from those at high Mach numbers. That really did relieve the Reaction Engines team of some notoriously intractable intake optimisation problems. That they now think it is worth grappling with those problems for the sake of lower orbiter mass is the bit I find interesting.
Interim HOTOL (the one using the An-225) was not Alan Bond team but BAe, after the two went their own, separate ways (REL was funded in 1989).
Of course if Interim HOTOL had actually been advanced then StratoLaunch would have had something to point at they could carry :)

Randy
Randy,

I hear you - I've been kvetching rather unsuccessfully about this very same fact over at https://www.secretprojects.co.uk/threads/stratolaunch.14179/...

Martin
 
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Archibald

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Martin: there is a whole bunch of papers from the decade of the 2000's - Sorensen / Bonometti "Crossbow", David J.Salt, DARPA / NASA "air launch grand trade studies", and M. Sarigul-Klijn that indeed show the advantages of air-launch. Cuts into the gravity losses, brings the delta-v to orbit tally from 9.2 km/s to barely 8 km/s.
If you are interested I will make a massive post on this forum.
 

Archibald

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Heck don't start me on this. Since 2008 I have downloaded like crazy, I lost the count of all the Pdf I have (in fact I never, ever tried to count them... and I have a degree in archives, supposedly) :p
a rapid count just said me I have 6104 files, and it is a very uncomplete backup. I must have 5000 pdfs.
(I did not dare to write "a massive dump" because of possible scatologic interferences, you nver know, with foreign languages)
 

martinbayer

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Archibald, I'm aware of a few authors you mentioned, but I'm definitely interested as well.
 

Archibald

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Chose promise, chose due (as we say in french) :cool:
 

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steelpillow

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Thank you!
If you still have a record of the source urls (being a good archivist!) you could just post those.
 

Archibald

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ha ha you have a point.
Unfortunately, no, I didn't kept the URLs, for many reasons, the idiot Frank Wolf (am I allowed to use the world idiot ? just asking, because Frank Wolf is an idiot, and there is no other word to call him that it is not rude) being a major one. Also not all downloadings were exactly *legal* (hrrrmmmm). Finally they come from a helluva amount of different sources.
 

RanulfC

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ha ha you have a point.
Unfortunately, no, I didn't kept the URLs, for many reasons, the idiot Frank Wolf (am I allowed to use the world idiot ? just asking, because Frank Wolf is an idiot, and there is no other word to call him that it is not rude) being a major one. Also not all downloadings were exactly *legal* (hrrrmmmm). Finally they come from a helluva amount of different sources.
That last bit is especially true in trying to find them around the web :)

If you can even find them which is becoming harder to do as well. And even then I've noted a trend where certain links tend to overwhelm a search result as well. So thanks Archibald :)

Randy
 

Archibald

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m
ha ha you have a point.
Unfortunately, no, I didn't kept the URLs, for many reasons, the idiot Frank Wolf (am I allowed to use the world idiot ? just asking, because Frank Wolf is an idiot, and there is no other word to call him that it is not rude) being a major one. Also not all downloadings were exactly *legal* (hrrrmmmm). Finally they come from a helluva amount of different sources.
That last bit is especially true in trying to find them around the web :)

If you can even find them which is becoming harder to do as well. And even then I've noted a trend where certain links tend to overwhelm a search result as well. So thanks Archibald :)

Randy
maybe I could open a thread somewhere on that Forum called "Archibald treasure trove" and start posting all that stuff ?
On my HD it is grouped in broad themes (quite broad at times)
In The bar section maybe ?

To Overscan and the mods - any issues ? broadband copyright something else ?
 
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