Rebel Engineers Talk To NASA

[MSimon]

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http://www.popularmechanics.com/science ... 44095.html

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[djolds1]

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http://www.popularmechanics.com/science ... 44095.html

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The contemptuous take on the same issue:

http://nasawatch.com/archives/2010/01/d ... usion.html

[93143]

The guy at NASAWatch seems to have an irrational hatred of DIRECT. Maybe it's because they inadvertently sicced Gaetano Marano on him...

[Heath_h49008]

Gentlemen, I think it may be a moot point if they have the heat exchanger issues fixed with their engine design...

http://www.youtube.com/watch?v=3H7BeyQOnPk

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

[Josh Cryer]

The NASAWatch guy is kind of schitzo, all of the anti Ares I stuff came from Direct proponents or advocates inside NASA. He was happy to post their reports.

[93143]

Gentlemen, I think it may be a moot point if they have the heat exchanger issues fixed with their engine design...

http://www.youtube.com/watch?v=3H7BeyQOnPk

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

Not necessarily. Skylon is 10 years away and much lower confidence.

I'm a huge fan of Skylon, but trying to break a Mars mission into 15-ton chunks that fit in Skylon's payload bay could well be significantly more expensive than just launching it on a half a dozen Jupiters. Never mind the fact that the early, low-flight-rate Skylon launches won't really be any cheaper than Jupiter... Heavy lift has its place.

But that's an argument for another thread (ie: didn't we just leave this party?)...

[Skipjack]

I'm a huge fan of Skylon, but trying to break a Mars mission into 15-ton chunks that fit in Skylon's payload bay could well be significantly more expensive than just launching it on a half a dozen Jupiters. Never mind the fact that the early, low-flight-rate Skylon launches won't really be any cheaper than Jupiter... Heavy lift has its place.

This is where I absolutely do not agree. I think that especially a high flightrate is what makes a launcher cheaper. The lower the flightrate, the higher the price and the risk as well.
Yes the first few flights might be expensive, but and I am sure of that, they will still be much cheaper than anything else, including a heavy lifter.
Plus, when does NASA ever get any cost estimates right?

[93143]

I said "low-flight-rate". The initial market is what we have now, and even Reaction Engines admits the current market is not big enough to get Skylon much below Falcon 9 - which as I've calculated before is roughly equivalent to Jupiter (assuming Jupiter gets a decent flight rate going) even if SpaceX manages to hit its cost targets.

Naturally if things take off, Skylon's costs drop by a factor of at least 10...

Also, Jupiter's costings are mostly Shuttle costings, with hefty margins added where the DIRECT team thought it prudent. They're pretty solid, and anyway The Aerospace Corporation produced roughly the same result in their analysis for the Augustine Commission (which then got ruined by the Commission's attempt to stretch out HLV development without regard for the fixed-cost penalty thus incurred)...

Also, it may not matter even if Skylon is free - it will still be far easier, and thus probably cheaper overall, to design and integrate a large interplanetary mission in Jupiter-sized loads than in Skylon-sized loads. Propellant and small pieces can go up on Skylon, but not everything. I would not be at all surprised if limiting components to 15 mT and the volume of Skylon's payload bay turned out to make a Mars mission prohibitively difficult and expensive...

[kunkmiester]

With the margins indicated, even fuel might be easier on a Jupiter--you'd just be getting a whopping buttload at a time, rather than the smaller trickle from something like Skylon.

Leave light lift for humans, and maybe for returning stuff to earth. Everything else goes up on a Jupiter.

If you went to integrating large numbers of satellite launches into single Jupiter launches, would that be practical?

[93143]

No no. Fuel is Skylon's job, for sure. It's not a trickle if you can launch a Skylon every couple of days, versus a Jupiter every month or so. That's twice the upmass even if you only have one Skylon, which shouldn't be the case... (You can obviously salvo two Jupiters, and since the VAB has four High Bays you could potentially do this twice in a fairly short period of time, but DIRECT thinks a sustained flight rate of about 12 per year is optimum for Jupiter - the flight rate would have to be a lot higher than that to get the price down much further.)

The flight rate is the key to Skylon's magic. If you've got something that needs lots of launches, and they don't particularly need to be huge, put Skylon on it and the price will go through the floor. It's what Shuttle was supposed to be - expensive to develop, fairly expensive to build, dead cheap to operate. And with the low turnaround time Shuttle was never able to realize.

This applies for small satellite launches too, not just propellant. Jupiter is for when shoehorning something into Skylon's payload mass and volume capacity is either an expensive PITA or outright impossible.

Of course, if Skylon hits a roadblock or fizzles, we're stuck with SpaceX, which isn't bad but doesn't have a vast advantage over Jupiter. Give them the flight rate and they should do okay.

[CaptainBeowulf]

But that's an argument for another thread (ie: didn't we just leave this party?)...

The TalkPolywell party... you can check out anytime you like, but you can never leave...

[DeltaV]

Have we crossed the event horizon yet?

[Heath_h49008]

If Skylon has the heat exchanger issues dealt with, Why should they be 10 years out? The airframe is simple.


If they have the engine, we can blow the dust off the X-30 wind tunnel data, and tell Lockheed to fire up the CNC mill.

The shape and engine positioning design they show is silly. You want as near centerline thrust as is possible. Can you imagine the yaw in an engine out situation with the one they picture?! Ouch!

[93143]

Skylon is a British design, so no Lockheed Martin (hopefully some Buy American rule doesn't prevent NASA from leveraging it...). Reaction Engines has a plan, and the plan says 10 years to IOC. Heck, it could easily take 10 years to build Jupiter if the program got unexpectedly squeezed for cash, and Jupiter is much more of a technological slam dunk than Skylon...

And the shape is actually very well thought out.

HOTOL's big problem was that the engines were at the back, meaning the centre of gravity was at the back, which made it horribly unstable during reentry, which ended up reducing the payload too much. Skylon has the engines in the middle, which solves that problem.

The reason they're so far apart? Well, this is just a guess, but I suspect that if they were any closer to the main aeroshell, they'd be roasting it with their exhaust plumes...

Engine-out is probably LOM anyway. This is an SSTO, after all...

[kunkmiester]

What's LOM?

It also seems from some of their pictures that there's four engines in each nacelle. If so, you'd probably need to loose quite a few to cause trouble.