Venturestar reborn?

[GIThruster]

http://phys.org/news/2013-09-experiment ... orbit.html

[GIThruster]

Not stuck on horizontal:

http://www.space.com/22836-military-exp ... darpa.html

[GIThruster]

Just checked: Grasshopper doesn't qualify since it makes its first stage sep at Mach 6 as opposed to Falcon's Mach 10.

If Grasshopper can't do what DARPA wants, what can?

"The reusable launch system technology is under consideration for both the Falcon 9 and the Falcon Heavy launch vehicles. It is particularly well suited to the Falcon Heavy where the two outer cores separate from the rocket much earlier in the flight profile, and are therefore moving at slower velocity at stage separation. If the technology is used on a reusable Falcon 9 rocket, the first stage separation would occur at Mach 6 (4,100 mph;6,500 km/h) rather than the much faster Mach 10 (7,000 mph;11,000 km/h) for an expendable Falcon 9, in order to provide the residual fuel necessary to complete the deceleration and turnaround maneuver, as well as the controlled descent and landing.[1]"

http://en.wikipedia.org/wiki/SpaceX_reu ... ing_system

Of course, if the DARPA requirements are loose enough, the 2nd stage of Grasshopper seems would more than fit the requirement, so long as it can be launched every day for 10 days. Not really sure that's possible.

[kunkmiester]

That doesn't look like Venturestar, but Dyno-soar.

[GIThruster]

The artists rendition has nothing to do with the DARPA requirements. As is seen in the second link, they are no even focused on Horizontal launch and land. It's an open field for people to press forward on tail sitting rockets like the Grasshopper.

A slightly larger Grasshopper first stage could go single stage to suborbital Mach 10, and still land itself. I think Musk will be all over this.

[djolds1]

That doesn't look like Venturestar, but Dyno-soar.

It looks like Black Horse.

[GIThruster]

IIRC, the original Venturestar concept would have taken only a tiny performance hit from using SSME's instead of the Aerospike. Given a LiAl tank or a properly wet-filament wound composite tank, and SSME's, Venturestar would more than meet the DARPA requirement. If I were at Lock-Mart I'd be dusting off the specs ASAP.

[GIThruster]

Just checked: Grasshopper doesn't qualify since it makes its first stage sep at Mach 6 as opposed to Falcon's Mach 10.

Ooops. . .em. . .given Grasshopper is expected to lift a second stage, it seems to me entirely possible it could reach Mach 10 while carrying enough fuel to land without the additional stage. I think that means the only requirement it might not meet is the cross-range and I'm not familiar with the details of this. Could be Musk already has what he needs for the DARPA offering?

[GIThruster]

I'm surprised no one is posting here! Where is Skippy?

Just as a note about tail sitters: the reason DOD is not much interested in vehicles with no cross range, like Grasshopper; is that for things like polar launches, cross range is necessary. With all these craft, single orbit aborts are considered significant safety ability, but because the world turns, polar launches cannot return to the launch pad without significant cross range ability.

The Grasshopper does not have significant cross range ability.

However, Grasshopper does prove out much of the engineering needed for a tail lander like DC-X. DC-X was much like Grasshopper, save that it's much wider body allowed for significant cross range. Of course, DC-X got it's larger body from use of H2, like the X-33/Venturestar.

So in a nutshell, if DARPA continues to REQUIRE cross range ability (something Skippy hates), then you're stuck with H2 engines rather than RP-1. And H2 engines to date need more maintenance than can be allowed with single day turnarounds.

I say, leave off the cross-range stuff. It's too difficult a task used too infrequently. If DOD knows better that they really NEED to launch polar, then they should make that case rather than simply require it.

[Skipjack]

This thing is not going to go to orbit, but is only going to fly a suborbital trajectory at mach 10. This means that you do not have to deal with the need to return to the launch base after only one polar orbit (as the vehicle never goes to orbit).
Also, you can actually make VTOL vehicles with a sufficient cross range. A good example would be the DC-X project which would have resulted in a VTOL suitable for DOD use.
A design based on the F9 1.1 (F9R) first stage should be able to fulfill the requirements pretty well. The current changed trajectory and mach 6 stage separation speeds are based on the need to return to the base after having accelerated a full first stage and more than 10 tons of payload. Darpa only wants 45 kg payload. That would require a MUCH smaller second stage, if any at all. I actually think that SpaceX could almost make the Falcon 9R first stage (or a slightly modified derivative of it) an SSTO with such a small payload requirement (which then is a problem with the cross range though).
The more problematic requirement is the rather short maintenance time. I dont think that SpaceX can do that with their current design.
So this is definitely an interesting project. I just hope they dont give the job to Lockheed again. Lockmart does not have a history of delivering much in government contracts lately...
The Venturestar was a flawed design and I would not go back to that for sure. Plus Lockmart spent way to much on just the suborbital prototype (X33) to make this project worth its money. For the same reason, I also hope that this wont be a single contractor cost plus programme this time.