SpaceX Grasshopper 744m Test Video. Stunning!

[tridim]

[Warren DeMontague]

1. So fucking awesome.

I'm not thoroughly convinced the energy expenditures vs. cost savings justify powered flight up AND down, but the concept is extra fucking cool regardless.

And the potential applications in terms of landings on other bodies, speak for themselves.

[BlueStreak]

4. Energy expenditure

I share your skepticism about that. Basically this would have to carry twice as much fuel as the rockets that can't descend under control. And when we are talking about lifting to geosynchronous (as opposed to just going up a half mile for a photo op) the payload is already limited to about 3% of the total weight.

The control system is definitely cool and impressive, but Musk seems to have this "then the laws of physics suspend just for me" attitude with both this project and Tesla.

[Warren DeMontague]

5. Actually I think Tesla has been pretty successful.

The fact that Elon Musk is behind this makes me far more inclined to suspend my skepticism. He's pulled off a lot of things other people wouldn't be able to.

[BlueStreak]

7. He has fundamentally miscalculated the energy capacity of battery storage

He approached Tesla the same way he approached Paypal, with an assumption that technology would do the "Moore's Law thing" so he didn't really have to worry about that. But in fact, we are approaching the theoretical densities of what we can store in the kind of batteries suitable for cars. That makes Tesla more or less a curiosity rather than a generally practical vehicle for the future. That's not to say he hasn't had an impact. He has. But I see Tesla as the finest product that can be produced on that dead-end road.

And likewise for rocket power, I doubt he can come up with a way to make rocket propulsion twice as efficient as all the rocket scientists that have gone before him have been able to do. And that's what you have to do to do a powered return.

Maybe he will prove me wrong. But let's see him use that approach when traveling to -- and returning from -- satellite altitudes.

To be fair, it doesn't take as much fuel on the return trip because the return weight is a small fraction of the launch weight, so maybe the numbers will work out for him.

[Warren DeMontague]

9. Give the guy a little credit. He put together an orbital-capable launch operation in the space

Of a decade or so.

Whether or not this particular idea pans out, the Falcon is an impressive piece of machinery.

[architect359]

17. +1

Thanks.

[caraher]

6. Actually, his attitude is, "I know the laws of physics"

He is trained in physics, after all, and credits that part of his education for much of his success:

L: You had stated in an interview recently that one of your pieces of advice for people looking to innovate is to "study physics and learn how to reason from first principles rather than reason by analogy." Can you expand on what you meant by that?

M: Of necessity, physics had to develop a framework of thinking that would allow understanding counter-intuitive elements of reality. Something like quantum physics is not very intuitive, and in order to make progress, physics essentially evolved a framework of thinking that was very effective for coming to correct answers that are not obvious. And in order to do this, it requires quite a lot of mental exertion. One cannot conduct one's everyday life reasoning from first principles; it would just require too much mental energy. So I think you have to operate most of your life with reasoning by analogy or essentially copying other people with minor variations. But if you are trying to break new ground and be really innovative, that's where you have to apply first-principle thinking and try to identify the most fundamental truths in any particular arena and you reason up from there. This requires quite a bit of mental exertion and I can give you some examples of how this helps one in the rocket business.

[BlueStreak]

8. Just to be clear, that's a Bachelor's degree.

But that should be enough for him to appreciate some of the fundamental limits. We shall see if his numbers add up.

[soniasharp]

10. Not a completely controlled descent

Actually, the real reusable rocket won't be firing all the way down. This is essentially just a test of the final few seconds of landing. In reality, there will be 2 separate short burns to bring the stage back - a deceleration burn, and then a final burn close to the ground for a soft landing. It only needs a very small fraction of the total initial fuel to achieve that. SpaceX is achieving some incredible stuff, I'm willing to bet they'll have a first stage recovered by the end of next year.

[BlueStreak]

11. So which stage is this test simulating?

[soniasharp]

13. First stage (kinda)

Well, essentially the same landing method can be used in landing both first and second stages. But Grasshopper was specifically intended to simulate the Falcon 9 first stage tank. Second stage recovery is a little more difficult naturally, since it has to deal with larger speeds and harsher atmospheric re-entry conditions than the first. Have to start somewhere.

[Warren DeMontague]

16. Welcome to DU.

[gopiscrap]

15. Welcome to DU

cool name btw

[Kablooie]

2. Looks kind of old fashioned.

Rockets could do this back in the 1950's.

In movies.

[hunter]

12. Or in Ray Bradbury books...

[BlueStreak]

14. Rockets could do this for real in the 1960s

OK, maybe not a controlled landing. That's a neat trick, and fun to watch. But the walleye missile had a very advanced guidance system.

http://en.wikipedia.org/wiki/AGM-62_Walleye

I know several mechanical engineers who worked on this project. Almost every day I drive by the research facility where they designed that. It was capable of directing the missile to fly down a stairway to reach its target, for example.

[Cooley Hurd]

3. Holy Shit!!!!!

doesn't even cut it!!!!!!

I love these guys!!!! Elon Musk and his team are AWESOME!!!!