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[IMAGE] SpaceX Falcon 9 Launch Profile


Caelib
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10 hours ago, Mitchz95 said:

6 meters per second? By KSP standards that's cutting it pretty close. ;)

Considering the forces that the booster survives at launch, when it's 10x as heavy, a 6m/s landing doesn't sound that horrible.  Spread over the 1-2m flexibility of the legs it doesn't seem that bad.  It would be rough on a human but easily survivable in a good seat.  The deceleration burn(s) might be nearly as brutal.  6 would also be the max, with 6.1 probably breaking parts and writing off the entire booster.

Edited by Sandworm
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 Yet only 95km down range. The second stage is practically doing all the work.

I wonder how SpaceX dictates trajectory and burn time for a given payload. Do they fly the same trajectory and burn longer or do they burn for the same time then fly a more efficient trajectory?

My RTLS efforts have been very successful, but it's tricky because of that. My rocket has a payload range between 10 and 30 tons. Far more without RTLS. MECO occurs at 30km with 900-1100 Dv remaining depending on my trajectory. 

So I wonder which is more important. Burn longer or fly shallower. Or a combination of both.

Edited by Motokid600
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1 minute ago, Motokid600 said:

Not surprised. Its just.. one cant help but think how much money all this is saving as opposed to just using a smaller disposable rocket flying a regular trajectory.

Let's not ignore the nine engines and associated plumbing that aren't being smashed into the ocean. Also bear in mind that the trajectory is not completely insane, yes it's not the most efficient but its not bad by any stretch of the imagination

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Do remember that first stage needs to haul entire stack 3\4 of way to space. Through densest atmosphere , fighting against aerodynamic forces. Second stage takes over when there is little to no gas around - which also allows for better Isp.

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The first stage may not go very far compared to the second stage or nearly as fast but it does literally do most of the heavy lifting, and represents much of the cost of the rocket.  Assuming that they can really easily reuse them getting those 9 rocket motors back is huge.

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Something I've been thinking about is how much easier upper stages have it.

1. No fairing or interstage, in some cases they don't have to stand up to any dynamic pressure

2. Higher nozzle expansion ratio (higher isp)

3. Lower TWR (more fuel for a given engine)

4. Lighter structure in general due to lower forces (although not really in the case of F9, the upper stage can pull 3+ G's)

Tbh I'm sure there are more but I don't wanna get too far off topic.

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  • 3 years later...
On 1/12/2016 at 12:23 PM, KerbonautInTraining said:

Guys, it says the max vertical speed is 6 m/s. That's some pretty robust landing hardware if you ask me.

Has a booster hit at 6 m/s and survived?  Some of them have come down pretty hot, this might be more a real number than a calculated one.

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