Comments on: SpaceX wrapping up Falcon 9 second stage investigation as it moves on from Grasshopper

By: Dudely

Dudely — Thu, 07 Nov 2013 14:33:16 +0000

The picture was taken from an aircraft using a powerful zoom lense. So there is an extreme angle and lots of atmospheric blur causing it to look weird. It really is 3 meters away. The engines are actually IN the spray so you can’t see them.

By: Dudely

Dudely — Thu, 07 Nov 2013 14:31:06 +0000

Actually they tried using chutes on Falcon 9 v1.0 and abandoned it. It’s just not workable for what they’re trying to accomplish.

This is actually their second attempt at reusability.

By: JohnG

JohnG — Tue, 29 Oct 2013 13:26:04 +0000

Spacex did not truly engineer their parachute recovery system. They bought some off-the shelf cargo parachutes and attached them to the booster. It was not a serious attempt at recovery, it was a why-not experiment carried out after the mission objectives were satisfied, which is a fine approach, BTW. However, the stage structure was not designed to survive the reentry/ deceleration forces and it came apart. Those results have no bearing on the viability of parachute recovery. Even in a boost back mission there may very well be an application for a parachute to provide passive orientation, ullage force, etc.

By: JohnG

JohnG — Tue, 29 Oct 2013 13:18:14 +0000

The SRB parachute systems added about 5% to the return weight of an SRB. What’s 5% of an F9, 2000-2500 lbs? The SRB was also a much tougher steel structure that could take the forces of reentry deceleration. The light structure of an unreinforced liquid stage cannot survive that without a retro burn. The question is, what method takes less mass, and facilitates reuse better. If boost back fits the requirements better, that’s your answer. That said, those that just write off parachutes as an obsolete technology are just as closed minded as those that say boost-back can’t be done.

By: Roger

Roger — Mon, 28 Oct 2013 15:43:29 +0000

SA’s advantage is no planes flying overhead, since it’s near White Sands Missile Range.

By: Rod

Rod — Sat, 26 Oct 2013 18:19:50 +0000

Interesting pic. But judging from the location of the spray relative to the bottom of the rocket, and knowing the length of the stage, I’d say it was more like 15 meters from touchdown. The pic seems to show the engine still firing (or just in the process of stopping) so they must have been really close to success. I was thinking that the engine had quit at a much higher altitude than what this shows.

By: DocM

DocM — Sat, 26 Oct 2013 02:37:20 +0000

The SRB’s dropped off lower down and slower. When SpaceX tried them with the lighter/smaller F9 1.0 cores they didn’t survive. Adding energy isn’t going to fix that.

By: Ben H

Ben H — Fri, 25 Oct 2013 02:10:27 +0000

What’s with the attempt to use an engine relight to slow down the Falcon 9 v1.1 first stage before water impact? Why not just use parachutes? Worked fine for the SRBs.

– Ben

By: Lori Robin

Lori Robin — Wed, 23 Oct 2013 06:20:44 +0000

Gwynne Shotwell is a rock star! AWESOME!!

By: Robert Clark

Robert Clark — Wed, 23 Oct 2013 05:35:58 +0000

Jeff, can you get a firm answer on the question of whether the F9R-1 test vehicle will have 9 engines or not? The statement from Shotwell that it will be “as flight-like as possible” suggests it will have all 9 engines. But discussions on NasaSpaceFlight.com suggest it will only have three.
Giving this test vehicle only three engines would make sense since only three are used during the actual descent, and you would avoid an expensive loss of all 9 engines during a failed test.
However, giving it all 9 engines and a full fuel load does have an advantage. If you apply the rocket equation to the claimed 311 s Isp and 20+ mass ratio of the stage, you see the first stage can be SSTO. This would be a major technical advance for SpaceX to accomplish.

Bob Clark