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Background on the Falcon 9 Launch

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Re: Background on the Falcon 9 Launch

#61
post #51

I'm having some trouble with the opening salvo here: "Now imagine placing a marble somewhere on that slippery sheet -- it is guaranteed to fall into one of the funnels. " This holds for the case where there are two objects initially at rest, but I don't see it as obviously true if there are more than two objects in the universe.

This was lovely writing, and successfully enlightened me on a few points, but my mind immediately saw the marble deform the sheet. I'd suggest a ping-pong ball and a frictionless sheet for a less perplexing thought experiment.

The marble can deform the sheet and it still works.

Re: Background on the Falcon 9 Launch

#62
post #46
post #39

Earlier quoted context omitted.

In most companies the "Posts from the CEO" are a group effort (at my last company I wrote multiple statements that were supposedly from our CEO). What you're attributing to a single person is actually the work of many. This leads to your question: > But, I'm just in awe and I keep thinking 'how does he do it?'. What can us, mere mortals learn from him? We can't change our baseline raw intelligence (which effects how…

>In most companies the "Posts from the CEO" are a group effort (at my last company I wrote multiple statements that were supposedly from our CEO). What you're attributing to a single person is actually the work of many. If it's a group effort he was being pretty deceptive by ending with "apologies for typos in the above," making it sound like he just dashed it off himself.

Don't underestimate a good copywriter :) Christian Rudder's 'Dataclysm' has a funny example of someone who copy-pasted the same message to dozens of people on OK Cupid complete with an apology for spelling.

Re: Background on the Falcon 9 Launch

#63
post #22

Nice article, but I couldn't pass up a chance to correct Elon Musk's math: It is important to note that the amount of energy needed to achieve a given velocity increases with the square, so going from 1000 km/h to 2000 km/h takes four times as much energy as going from 0 km/h to 1000 km/h, not twice as much. Three times, not four--you already spent a quarter of the energy getting to 1000 km/h. Getting the rest of the…

I believe you've misunderstood his English. If it takes 1 Joule to accelerate the mass from 0-1000km/h, it will take 4 Joules to accelerate the same mass from 0-2000km/h. Elon is calling that four times as much as because he's considering the total energy required to accelerate from 0 in both numbers. I think you're just accounting for it differently by saying it takes 3 times as much as the original energy input to…

I think panic is correct. "from 1000 km/h to 2000 km/h" means from 1000 km/h to 2000 km/h, not 0-2000 kph. Though presumably Elon was thinking of the latter.

Re: Background on the Falcon 9 Launch

#64

Clearly this man's intellect is through the roof. Reading this post and him explaining these concepts in such first-principle terms (despite not being a physicist/rocket engineer) indicates his in-depth understanding (nothing new there). I know he has a Bachelors in Physics but bear with me. But, I'm just in awe and I keep thinking 'how does he do it?'. He's running two intensely technical and risky companies. Yet he…

Try explaining to someone an easy to understand version of your life's work, it probably comes out pretty easy. Same thing here. The impressive part is Elons explanation about the science is not typical CEO material

Re: Background on the Falcon 9 Launch

#65

Earlier quoted context omitted.

SES already said that they're willing to be the first customer for a used booster[1]. Before they get that far, it'd be interesting to see if SpaceX flies a used engine, since they've got "one engine out" capability. Which has already been tested twice. 1: http://spacenews.com/spacex-early-adopter-ses-ready-to-reuse...

That article raises an interesting point I really hadn't considered, who owns the first stage? If you pay "full price" for a launch and SpaceX recovers the first stage to re-use, did the person who paid to launch it own it or does SpaceX? It was presumed lost of course. No doubt there is language in the contracts about that. Would be interesting to see a launch contract.

SpaceX own the first stage.

You pay to get your payload delivered to a specified orbit. You don't actually buy the rocket.

It's like flying, you buy a ticket, not the plane.

Re: Background on the Falcon 9 Launch

#66

Clearly this man's intellect is through the roof. Reading this post and him explaining these concepts in such first-principle terms (despite not being a physicist/rocket engineer) indicates his in-depth understanding (nothing new there). I know he has a Bachelors in Physics but bear with me. But, I'm just in awe and I keep thinking 'how does he do it?'. He's running two intensely technical and risky companies. Yet he…

> despite not being a physicist/rocket engineer

The article's description of newtonian mechanics of orbits and energy is freshman physics stuff, and every engineer should know it.

Nevertheless, Musk is an astonishing man and I suspect he'll go down in history as one of the greatest engineers. I wish I could buy a few shares of SpaceX and own a tiny morsel of the dream :-)

Re: Background on the Falcon 9 Launch

#67

Clearly this man's intellect is through the roof. Reading this post and him explaining these concepts in such first-principle terms (despite not being a physicist/rocket engineer) indicates his in-depth understanding (nothing new there). I know he has a Bachelors in Physics but bear with me. But, I'm just in awe and I keep thinking 'how does he do it?'. He's running two intensely technical and risky companies. Yet he…

Try explaining to someone an easy to understand version of your life's work, it probably comes out pretty easy. Same thing here. The impressive part is Elons explanation about the science is not typical CEO material

The analogy of the membrane with weights placed on it is pretty standard, I encountered it in the 1970's, and have seen it on episodes of Nova.

Re: Background on the Falcon 9 Launch

#68
post #3

One thing I've not seen mentioned in the coverage so far: how much payload is sacrificed by the need to keep fuel in reserve for the return to base? I'm guessing the sacrifice is roughly equal to the mass of unburnt fuel in the booster at the point of booster separation, but don't much trust my intuition on these things.

> how much payload is sacrificed by the need to keep fuel > in reserve for the return to base? Simple answer: None. A more detailed answer is that building a system which can be reused is an economic proposition. So that the Falcon 9 can lift X Metric tons to orbit for $Y. The way in which they keep the value $Y low is by re-using the first stage. Every satellite project knows the throw weight of all the common launc…

The jet engines on the Me-262 jet fighter were only good for 10 hours. (The airframe didn't last much longer, and so the Germans didn't bother with things like corrosion protection.)

Even so, a lot of expensive parts on the rocket likely have much longer service lives.

Re: Background on the Falcon 9 Launch

#69

Earlier quoted context omitted.

That article raises an interesting point I really hadn't considered, who owns the first stage? If you pay "full price" for a launch and SpaceX recovers the first stage to re-use, did the person who paid to launch it own it or does SpaceX? It was presumed lost of course. No doubt there is language in the contracts about that. Would be interesting to see a launch contract.

SpaceX own the first stage. You pay to get your payload delivered to a specified orbit. You don't actually buy the rocket. It's like flying, you buy a ticket, not the plane.

Just for reference, I got an inside look at what it took to get OSCAR16[1] launched and it isn't like flying :-). Now I don't doubt things are more streamlined now but every launch starts with a basic contract and that contract has to cover everything from contingencies to insurance to liability to disposal.

Trying to search for a boilerplate launch contract I found an article[1] where it discusses that Spaceflight Industries bought a Falcon 9 launcher [emphasis mine] which suggests that one buys the entire rocket. That would imply that if they land it, you still own it does it not? Can you then go over to the landing zone pick up your rocket and resell it for parts to offset your original purchase price? :-)

I am really confident that ownership of the first stage is covered in the launch contract if it is returned to the landing field. And the math there would no doubt be really interesting to an insurance company since you have the possibility that the launch is a success and the first stage lands, the launch is a success and the first stage crashes, the launch effectively fails (second stage failure) but the first stage successfully returns, and both stages are lost. That is a number of different outcomes to insure.

Frankly my mind is boggling at the potential legal complexity here.

[1] https://en.wikipedia.org/wiki/AMSAT-OSCAR_16

[2] "SpaceIL has purchased launch services from Spaceflight Industries; an American space company who recently purchased a SpaceX Falcon 9 launcher and will manifest SpaceIL’s spacecraft as a co-lead spot, " -- http://lunar.xprize.org/press-release/israeli-google-lunar-x...

Re: Background on the Falcon 9 Launch

#70
post #63

Earlier quoted context omitted.

I believe you've misunderstood his English. If it takes 1 Joule to accelerate the mass from 0-1000km/h, it will take 4 Joules to accelerate the same mass from 0-2000km/h. Elon is calling that four times as much as because he's considering the total energy required to accelerate from 0 in both numbers. I think you're just accounting for it differently by saying it takes 3 times as much as the original energy input to…

I think panic is correct. "from 1000 km/h to 2000 km/h" means from 1000 km/h to 2000 km/h, not 0-2000 kph. Though presumably Elon was thinking of the latter.

Read it as "going from target velocity of 1000km/h to 2000km/h".
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