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SpaceX’s Falcon Heavy successfully launches

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Re: SpaceX’s Falcon Heavy successfully launches

#531
post #192

Earlier quoted context omitted.

This is why I love the live streams hosted by John Innsprucker. He doesn't look like a TV star, he looks like an engineer, a rocket scientist. He looks real. The other hosts are great, but if you told me they were hired actors or PR people I'd believe it.

You're showing your biases here. The other people on the livestream are also rocket scientists. They aren't PR people. They just happen to be younger, or women, or of color. So you might want to re-evaluate what you think a rocket scientist "looks like", because your notion is outdated. Sorry to call you out like this, but these kinds of prejudices about who is the "correct" kind of person for tech jobs are harmful a…

Not to belittle your point, but in defense of the original comment, I think he looked "more like an engineer" because he looked like he'd been up for 48+ hours powered nothing by coffee

Re: SpaceX’s Falcon Heavy successfully launches

#532

Earlier quoted context omitted.

Star Wars takes place in the distant past, not in the future. Also, 2001: A Space Odyssey is a great movie about a great example why you do not pilot your ships with computers all the time. Also, you do not know what the future holds. You are living in the present, not the future, where we very well may have pilots piloting ships. Star Wars is not science fiction and it does not take place in the future. We are not l…

Isn't the key part of Sci-fi that it contains a society that has in some way advanced beyond our own? Saying it's not sci-fi because the fictional advance is set in our past (but at a development technologically beyond our own) seems quite a strange distinction.

No. The key part of SF is the "What if...?" question. A Science Fiction story should posit a difference about the setting from our own world and this difference should have consequences. Alternate history stories like "The Man in the High Castle" are Science Fiction. "What if the Nazis won?".

Likewise the key part of Romance genre fiction is the Happy Ending. It doesn't matter whether they sleep together (a lot of Romance aimed at older and Christian readers doesn't have any sex at all), or get married, but there must be a Happy Ending.

Re: SpaceX’s Falcon Heavy successfully launches

#534

Earlier quoted context omitted.

Should have, but didn't. At least not for manned spaceflight. We learned how to keep humans alive in space way back with the Gemini project. A long-duration orbital sojourn could have been had for the cost of the ISS. At the end of the day, I struggle to think of a single big thing we can do post-ISS that we couldn't without.

It may not make headlines, but the knowledge we have gained about long-duration human health in space from ISS is utterly beyond price. For all its problems, that alone makes ISS worth it.

I was not aware of this, do you have a link to any of that info?

Re: SpaceX’s Falcon Heavy successfully launches

#535

Did they need to modify the Tesla to make it vacuum worthy? Like, remove any fluids, remove any parts that might explode in the hot or cold of space, deflate the tires, etc. Note: I'm more interested in a scientific answer, as opposed to casual conjectures. Preferably from an engineer knowledgeable of such things. And specifically, the materials sciences aspect of how materials will survive in a vacuum.

As a mechanical design engineer (not of cars, of other vehicles) I can't think of any systems that you'd need to modify if you don't plan on driving the car again. This is all off-the-top-of-my-head theorycrafting, so I could be wrong.

Space is only -1 atmosphere and even then, it only affects sealed systems. For the rest, they'd equalise. Also, cooling in in space is actually fairly gradual as there's only radiation, not convection or conduction. Let's go through the systems and evaluate what that means:

For structural components, nothing will really change. After all, we built spacecraft out of aluminium before. The ISS has to cope with this more, as it goes in and out of sunlight every 90 mins, so it gets something like 15 cycles of high/low temperature a day. The thermal shock of going from darkness to sunlight is the main issue, but this won't be passing through the earth's shadow constantly since it'll be orbiting the sun, so changes will be far more gradual.

Bigger issues come from different materials joined together, such as steel to aluminium, since they expand at different rates, but that's not really a problem here and even if it is, it'll just crack a bit at the seam. That's not going to cause the car to explode into little fragments.

For unsealed systems with fluids, they'd just boil away in the vacuum before desubliminating into little frozen droplets and bounce around or whatnot.

The only sealed systems with fluids in them that I can think of are tyres and brake lines. Tyres tend to sit at about 30-35 PSI, which is ~2 atmospheres. They then have to endure significant heating/cooling, dynamic pressures of spinning, etc. so an extra atmosphere wouldn't cause issue from a pressure point of view. Ditto brake lines - you stomp on them with a mechanical advantage and they never rupture.

I think you'll find the worst damage will be to the paint over time, which will fade more aggressively since it's not protected from UV sunlight any more.

edit: I forgot the batteries, which I believe are a sealed unit. They might have just dropped the battery pack from the car. Not sure what a vacuum would do to them as I don't know enough about Li-Ion battery design to comment.

Re: SpaceX’s Falcon Heavy successfully launches

#536

Earlier quoted context omitted.

Star Wars takes place in the distant past, not in the future. Also, 2001: A Space Odyssey is a great movie about a great example why you do not pilot your ships with computers all the time. Also, you do not know what the future holds. You are living in the present, not the future, where we very well may have pilots piloting ships. Star Wars is not science fiction and it does not take place in the future. We are not l…

> Also, 2001: A Space Odyssey is a great movie about a great example why you do not pilot your ships with computers all the time. No, it merely illustrates why you want your AI properly bottled up and airgapped that way the flight computer will follow your instructions after you consult with the AI (assuming an AI is ever built...). Computers can control spacecraft just fine in the present without AI so really there…

Since 2012 the SpaceX Dragon capsule has been under AI control for rendezvous with the International Space Station for grasping and docking. It uses computer vision to estimate its pose relative to the ISS and steers accordingly.

Source: Andrew Howard of SpaceX, who is in charge of this software and has to endure the stress of each rendezvous. Screwing up could kill the ISS crew.

Re: SpaceX’s Falcon Heavy successfully launches

#537

Did they need to modify the Tesla to make it vacuum worthy? Like, remove any fluids, remove any parts that might explode in the hot or cold of space, deflate the tires, etc. Note: I'm more interested in a scientific answer, as opposed to casual conjectures. Preferably from an engineer knowledgeable of such things. And specifically, the materials sciences aspect of how materials will survive in a vacuum.

the car is not actually in the vacuum AFAI can tell from their GIF: https://tctechcrunch2011.files.wordpress.com/2018/02/spacero... id imagine a 360-camera is projected onto the inside of the sphere/case the car is actually inside of.

What are you talking about. That gif is showing the fairing separation. There's no sphere.

Re: SpaceX’s Falcon Heavy successfully launches

#538
post #482

Earlier quoted context omitted.

I don't see how that's much of a credit boost to the Soviet failures the parent is referencing. The Apollo program had the same constraints of lacking modern electronics and not knowing many of the things we know today.

The comparison was that N1 had a some 30 engines (Falcon Heavy has 27, given it's 3x Falcon 9's) and that was its downfall. In comparison, the Saturn V used only 5, they were just that much bigger. It's widely regarded that the 5 vs 30 was the difference as to why Saturn V was successful and N1 was not, as the Soviets simply had to roll too many dice in a situation where a failure resulted in complete mission loss. I…

It's interesting that in Soviet rocket engine school engines count by pumps, so, e.g. RD-180 is one engine, one pump, two chambers. In American rocket engine school engines used to count by chambers.

In this sense R-7 is remarkable because it has a good overall success record (most launched rocket) and 32 chambers working at liftoff. Some of those chambers are rather small - about 3 metric tons of thrust, about as much as main chambers on British launcher Black Arrow - but still.

Re: SpaceX’s Falcon Heavy successfully launches

#539

Raises some interesting secondary questions; Did the starman dummy contain telemetry? At lift off? Now? If I were SpaceX this is a good way to test your spacesuit, actually in space, if you instrument the dummy its on. Pressure sensors, temperature sensors, G sensors. Do they turn off the camera if its about to fly by something that would rather not be seen?

Elon said in the press conference afterward it was just a mannequin in the suit, no instrumentation.
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