Rebel Engineers Talk To NASA

DeltaV · Post by **DeltaV** » Mon Feb 01, 2010 6:38 pm

I wish Skylon the very best success, and feel it would be of great benefit to the world, but engine-out during high thrust is not a trivial concern, especially with such a complex, bleeding-edge engine design --

coupled with wingtip mounting and small rudder area --

The SR-71 has automated systems to deal with an 'inlet unstart' at high Mach, the idea being to restart (more precisely, return the shock to inside the inlet) before yaw diverges too far. If restart is not possible, the only remaining option is to compensate with rudders and quickly throttle down the remaining engine. Maybe RE should consider some sort of lightweight, tail-mounted, fast-acting, solid-rocket module to provide corrective yaw moment in the case of a single engine failure.

DeltaV · Post by **DeltaV** » Mon Feb 01, 2010 6:45 pm

kunkmiester wrote: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.

Unless a turbine fractures and breaches containment.

http://www.iasa.com.au/folders/Safety_I ... tated.html

Heath_h49008 · Post by **Heath_h49008** » Mon Feb 01, 2010 8:48 pm

Skylon's engine cut away may be pretty enough for investors, and inaccurate enough for potential competitors. Just a thought here. I think they may have solved the cooling issues by more than just a more efficient exchanger. I think they may have also found a better method of managing their cryogenics to reduce the amount required.

Hearing a rocket advocate bemoan the innate instability of an inverted force pendulum design is a bit odd.

(I couldn't resist the cheap shot)

Simple solutions... drop the engines before re-entry, fly them back under a steerable wing. (sloppy) The airframe is SO simple.... and I hate to repeat that, considering all of the stresses and cost issues... but compared to the initial development of YF-12 it really is.

Simpler solution...

IF the engine works... and IF it doesn't get locked down by a governmental body... Give a couple to Burt Rutan and the rest of the real innovators playing out in the market and stand back.

This tech is easily applicable to atmo-skip airliners, and cruise missiles, so if it works, it will be popular. Wind tunnels all whistle the same tune, and the airframe will be dependent upon the needs of the powerplant(s).

After all, nothing prevents us from putting this engine on a traditional rocket. Unless you really love lifting unneeded O2 that is.

DeltaV · Post by **DeltaV** » Mon Feb 01, 2010 9:22 pm

I generally hate the idea of using solids for propulsion, but they do have their uses. For emergency yaw compensation, I was thinking of something along the line of SDACS:

http://www.mda.mil/global/documents/pdf/05fyi0041.pdf

These are arrays of very small, quick burning, solid fuel thrusters, pointing laterally outward and fired in a computer-controlled sequence to approximate some desired lateral force vector.

MSimon · Post by **MSimon** » Mon Feb 01, 2010 9:32 pm

LOM = Loss of Mission

i.e. abort

MSimon · Post by **MSimon** » Mon Feb 01, 2010 9:42 pm

http://www.flickr.com/photos/asten/75815378/

I was there last summer. Family reunion. About 200 people. I had dinner under the SR-71. Also a couple of beers (open bar). The first mate. #2 son, #3 son, and #1 daughter, plus my mother were all there.

DeltaV · Post by **DeltaV** » Mon Feb 01, 2010 9:48 pm

Hard to believe it came from this world...

CaptainBeowulf · Post by **CaptainBeowulf** » Tue Feb 02, 2010 12:30 am

Have we crossed the event horizon yet?

We're waiting for them to turn the Large Hadron Collider back on...

choff · Post by **choff** » Tue Feb 02, 2010 1:44 am

It looks even more impressive when its standing almost vertically on its afterburners only a few hundred feet overhead.

DeltaV · Post by **DeltaV** » Tue Feb 02, 2010 2:25 am

The windscreen reached 550 F in cruise and was used by the crew to heat food.

Heath_h49008 · Post by **Heath_h49008** » Tue Feb 02, 2010 2:28 am

The best quote I ever read was... "You could always tell which engine had just 'un-started' because it was the opposite from the side of your head that was hurt."

A beautiful bird, that deserves an heir...

Betruger · Post by **Betruger** » Tue Feb 02, 2010 5:16 am

DeltaV wrote:The windscreen reached 550 F in cruise and was used by the crew to heat food.

Excellent.

Betruger · Post by **Betruger** » Sat Feb 06, 2010 4:46 pm

93143, If I argued the following (aside the fact that I sounded angry), how would you refute it?

You cannot build a plausible Mars mission out of 20-ton chunks, not with current technology and launch vehicles.
That statement is asserted with no proof. I don't accept it at all, unless what he means by "current technology" is NASA's current technology IN PLACE, AS IT IS. Then duh, but that's circular reasoning.

Tell me something which cannot be built reasonably efficiently from 20 ton pieces.

I can think of things incidentally ... a full-size civilian nuclear reactor (pressure vessel), a WWII battleship ... but the idea that one cannot build an interplanetary launch stack from 20 ton pieces strikes me as a very strange claim.

Also if you look at the claim
Even with moon missions, if you want more than one per year, Jupiter is cheaper than EELV, and the difference only grows with mission rate.
The "EELV" he's talking about is Delta, and he's assuming that the very optimistic claims for Jupiter costs (which of course are entirely speculative ... perhaps I should just be honest and saw "low balled" ... are real)

I think the claim that Jupiter will beat any routinely operating COMMERCIAL launcher on kg/$ to LEO makes no sense. Of course Delta is not really a routinely operating commercial launcher.

And one per year ... you so sure there would be one per year? One of my biggest objections to the big launchers is that they can't be even remotely economic unless you commit to a rather high launch rate.

Skipjack · Post by **Skipjack** » Sat Feb 06, 2010 5:39 pm

But Jupiter will never have enough launches to be cost effective. Just like the shuttle. Each individual launch will be too expensive and the total number of heavy lift launches that are needed worldwide is too low. That is why Ariane 6 will actually have LESS payload than Ariane 5 currently has. So a low cost, low payload vehicle with a higher flight rate will be cheaper than a high cost, high payload vehicle with a lower flight rate (or do you want to argue that the shuttle ever was cost effective?).

Edit:
The other thing to consider is that a lower cost LV, can open new markets. There are a lot of people that need very small payloads and generally satellites are getting smaller.

Betruger · Post by **Betruger** » Sat Feb 06, 2010 6:13 pm

I'm not arguing this. I'm curious to see how the arguments from 93143 and someone else on another forum play out. Unfortunately the other debater kind of refuses to play nice because he's jaded with debate.. From debating global warming with deniers. So if I want to see any action (actual brass tacks debate), I have to kick start things myself by either getting 93143 to show his math on the other forum or ask him nicely to tell me the basis he's arguing on, in brief, so that I can at least see how things stand.
It's the most satisfaction I'm going to get out of this whole new space policy thing. It's too time consuming to wade thru all the emotional arguments from everyone involved that otherwise would present polite, informed debate.

Here's the external thread.. Debater #2 is BadAndy.
I hope trying to spark this debate wasn't done too impolitely. In my experience there's more to learn from watching two sides of a particular subject of contention debate things, than just reading either one under vacuum.