Focus Fusion July Update and other stuff.

[GIThruster]

Well I stand corrected! but truly, I'm pretty sure X-37B must have something more advanced because it's got much higher loading. Now if that stuff were available to NASA, we might have some interesting designs on the table. As is, we don't.

For that matter, we could just scrap the aerospike and give tank construction to Scaled Composites, and we could probably revive the Venturestar program quite handily, even with no new TPS.

The way to do that is hand the ball to LockMart for development but with only limited promises if they fail to perform. Let them bare the brunt of failure but not enough to break them. . .motivate them to get the job done on budget and on schedule--something we've forgotten how to do.

Kelly Johnson didn't get paid for failure. . .so everyone busted their assess.

[Skipjack]

Unfortunately information on the details of the X33 and Venture star is getting more and more sparse as the years go by. A few years ago there was a lot more info on the TPS out there.
Here is some more good read on the X33 over all.
http://www.nasaspaceflight.com/2006/01/ ... -happened/

It also mentions the TPS here:

Not only was the program cancelled, but all the successful new technology was laid to rest along with the death of the X-33. The metallic TPS developed by BF Goodrich is still seen by some engineers as one of the most impressive parts that made up the X-33.

My guess is that it is now in the X37b and probably also used elswhere...

[Skipjack]

I would not do that. The Venture Star had quite a few issues. One of them was that Lockmart was not able to attract investors for the project. NASA did not want to spend any more money and they had some technical problems too at the time.
Personally I would rather do a DC-X style vehicle. It is easier to operate than the Venture Star would have been. I would trade some of the payload for that.

[Skipjack]

Oh, in regards to TPS, I can not wait for the results of tests regarding an MHD based design. Basically a strong magnetic field that prevents direct contact of the nose with the hot plasma, thus reducing the need for high temperature TPS in this area. This has been a pet idea of mine for 20 years. Finally they are doing some testing with that. God knows what took them so long.

[GIThruster]

I would not do that. The Venture Star had quite a few issues. One of them was that Lockmart was not able to attract investors for the project. NASA did not want to spend any more money and they had some technical problems too at the time.
Personally I would rather do a DC-X style vehicle. It is easier to operate than the Venture Star would have been. I would trade some of the payload for that.

I looked at the X-33 debacle more closely a few years ago and to be honest, if there was a single problem with the program, it was in systems engineering.

NASA didn't hire Scaled Composites, but instead a group with no expertise in building large composite structures. When the engineers gave shape to the vehicle, they were not aware that that shape would require many seams in the tank design, and that this would require the tank to not only weigh too much, but to weigh even more than the lithium-aluminum tank they already knew was too expensive. Then the aerospike people came forward with the fact they needed an enormous heat sink that would likewise add weight, and the design was dead. All of this would have been avoided with better systems engineering from the start, and working with people with real expertise. If the tank issue had not come up, a switch to more conventional thrusters might have been possible.

Something that is a cross between a tail sitter and a glider might be possible. Tail sit from LEO to ~100 miles and fly back the rest of the way would save a lot of propellant.

But looking at all this, without a really revolutionary propulsion system, probably no one is going to design a system that can beat Elon Musk as his game. Better is to design craft to fly past LEO and let Musk and the private sector compete for LEO service--IMHO.

[Skipjack]

If the tank issue had not come up, a switch to more conventional thrusters might have been possible.

No, they would not have had enough ISP. They already had to quite radically change the design in order to keep the payload.
Venture Star was meant to replace the shuttle in every aspect. It again was meant to be a heavy lifter, a black ops vehicle with a large cross range, a crewed vehicle and an orbital service platform.
All these requirements caused the shuttle to fail and they were what made the Venture Star fail. Also NASA wanted to put as many new technologies into a vehicle as possible, instead of relying on off the shelf parts. It was a failed concept from the start and a good demonstration of NASAs inability to manage LV design and construction.
The DC-X had a much different philosophy. Start with small goals and off the shelf parts and then gradually expand the envelope.
Arianne Space is currently downsizing from Arianne 5 for Arianne 6 because they have realized that they dont need a heavy lifter, which only raises the cost. Most of their payloads are much smaller.
A DC-X vehicle with a rapid turnarround would just need to transport 3 crew or the equivalent in cargo to LEO and that would make them plenty of profit already. Instead the thing would launch evey other day.
High flightrate = more cost efficient.

But looking at all this, without a really revolutionary propulsion system, probably no one is going to design a system that can beat Elon Musk as his game.

At least Musk wants to reuse his stages. I personally dont regard their designs very highly. They are very conservative. But at least they are cheap. In the current situation that is at least something. Would really love it, if they did something DC-X like though. The Merlin2 could bring that maybe.

[GIThruster]

SSME has higher Isp than the aerospike planned for X-33.

SSME= 453 in space, 363 at sea level.
Aerospike = 428 in space, 338 at sea level (and it weighs much more than SSME)

http://cobweb.ecn.purdue.edu/~propulsi/ ... s2200.html

It was a case of people wanting lots of new toys and not keeping their eye on the goal--a profitable transport system.

[WizWom]

SSME has higher Isp than the aerospike planned for X-33.

SSME= 453 in space, 363 at sea level.
Aerospike = 428 in space, 338 at sea level (and it weighs much more than SSME)

Yep, right now, Aerospike is an interesting concept, that might contribute but does not.

ISP is not the most important feature to orbit, nor is the rocket engine mass.

Tankage, rockets, pumps, control systems, ISP curve as you move through the atmosphere, all these things play a part.

LOX/RP-1 is probably the best choice for now. In a plain rocket like the Merlin-1D or Merlin-2.