Mad Rocket Scientist

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About Mad Rocket Scientist

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    Flight Director

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  • Location Gizmonic institute

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  1. SpaceX Discussion Thread

    Looks like the Q&A is down, hopefully they'll reupload an edit version with good audio. I stole this transcript from FutureMartian97 on reddit. (Edit: removed link just in case, it was on r/spacex) "How long will this take?" - I'm optimistic but i'm trying to re-calibrate, but we are building the first ship right now, and I think we can start doing the first up and down flights in the first half of next year. If rapid re usability works out we are confident we can get the cost of a BFR launch down to 5 or 6 million dollars. "How do you manage your time?" - At SpaceX 80-90% of my time is focused on engineering and Gwynne Shotwell handles the business side of things. And that video is the result of the great people at SpaceX. "Who are you inspired by" - Kanye West obviously. laughter "So why do all of these things?" - Well I thought to myself why are we not making progress in space? Where are the bases on the moon and the space hotels as promised? I looked at NASA's website and it never says when were going to Mars. There will also be no will to go to Mars if there is no way to get there. "Why is no one else doing these things?" - What's your pain threshold? "What was your biggest failure and how did it change you?" - Tons of failures along the way. For SpaceX, the first 3 Falcon 1 launches failed. Maybe if I was able to higher a better chief rocket designer, then maybe we would've had less than 3 failures. "How do you prioritize all your companies?" - For business stuff almost all time is dedicated to SpaceX and Tesla. For non business stuff it's my kids. Boring Company started as a joke because it sounded funny. "Why are you so concerned about AI?" - The biggest issue with civil AI experts is that they think they know more than they really do. Very close to the cutting edge of AI, and it scares the hell out of me. I think the dangers of AI are way worse than nukes. "What issues should the next generation be solving?" - Making life multi-planetary. Need to make sure there is a seed to keep humanity going in case of another dark age, possibly caused by a third World War. Sustainable energy is also really important. "What do you hope the world will look like when children born today are your age?" - Mostly transferred to sustainable energy, base on the Moon and Mars. Anyone can go to Mars or anywhere in the Solar System. Achieve symbiosis with AI. "What can you tell us about Starlink" - Internet for people with no internet, good for sparsely and moderately populated areas. Will be good to fund BFR. "What kind of government for the first Martian colony? Your position?" - Emperor or God Emperor? Really most likely direct democracy. Everyone votes on every issue. Keep laws short. If the word count on a law exceeds Lord of the Rings then it's to long and suspicious.
  2. SpaceX Discussion Thread

    Here's the official youtube video:
  3. Vacuum Engines

    Yes. Basically, the faster the exhaust, the higher the specific impulse, and the more efficient the engine is. And to get speed, you first need to make the area the flow is going through smaller, trading pressure for speed like a garden hose nozzle. But at supersonic speeds, that no longer works and you have to start expanding the area. The shape of this is called a de Laval nozzle, and looks like this: When the exhaust comes out of a rocket engine, it has very little pressure, and a lot of speed. When the pressure drops below the ambient pressure, it stops working very well, and can even destroy the engine, so atmospheric engine are designed to expand the exhaust to around sea level pressure, and vacuum engines designed to expand the exhaust to as low a pressure as possible, before the weight of the bell exceeds the benefit of higher specific impulse.
  4. That's interesting, I didn't know it was calculated that way for jet engines.
  5. Anyone here heard of Projectrho?

    This is an amazing website too: Very hard to navigate, but has loads of info on space stuff. Check this page too:
  6. Yes, but it's because the mass ratio is infinite, not the effective exhaust velocity * g0.
  7. I guess this is the right place to post this: EDIT: My opinion on the expansion is that I'm excited for it, and I'm going to buy it, but I'm also going to be slightly annoyed by the mismatch of part quality.
  8. SpaceX Discussion Thread

    It still seems odd, considering that they released the footage of failed landings. Plus, it reflects well on SpaceX that their rocket can land even in terrible situations.
  9. Boring company

    Ah, I didn't see any numbers on slip right at the fault itself. (Due to a lazy search) Thanks for correcting me. I wonder whether they figure the chances of a train being right at the fault during an earthquake is just low enough that it doesn't matter. If that's the case, then the sleds are no more dangerous. The hyperloop might be, depending on long it take for it to decelerate in emergency. I said not to do that! Yep, it looks like there's lots of slip. That photo brings up a couple of questions, though. First of all, why is it an S-curve, with both ends inline with each other? I imagine that a slip fault would just offset both ends, and leave a simple curve. Second of all, why is the ballast still straight? It seems like this might be a normal or thrust fault, which would explain the S-curve too; the rails have been shortened, causing them to buckle. Not to deny that it would be a problem for a tunnel, but it seems like tunnels aren't much more dangerous than other forms of transport during an earthquake.
  10. Boring company

    I've looked into this a bit, because I've seen it before, and it seems like earthquakes have not historically been very damaging to subway networks. I found this: And this: Both of which say that it is fairly safe. It seems that in the area around the fault, the ground shakes mostly uniformly, and wouldn't damage a tunnel. For one thing, the majority of injuries from earthquakes come from objects and loose parts of buildings falling. Don't quote me on this, but I think that at the fault itself, there isn't very much slip, and the energy of the earthquake comes from the fact that the fault is long and deep, so even a slip of a few inches means a lot of energy. EDIT: Turns out faults do slip more than I thought.
  11. Help calculating interplanetary transfers

    Ah, that makes sense. Thanks!
  12. I've been trying to calculate a transfer from earth to venus for my blog, but I'm stuck. Here's what I have so far: Source for constants: A transfer orbit between Earth and Venus depends on the position of the planets at departure and arrival. For this example, the position of Venus does not matter, as aerobraking will work at either of those speeds. Earth should be at apoapsis, because in this case we want to lose, rather than gain, velocity as Venus is in a lower orbit than Earth. Let's begin. First, the velocity of Earth around the Sun at apoapsis. We don't really need to calculate this, as it is well known: 29290 m/s. The transfer orbit is an elliptical orbit with its apoapsis at Earth's apoapsis, and its periapsis at Venus' apoapsis (I think this gives the lowest delta-v). This gives a semi-major axis of: (Radius of Earth's orbit at departure + Radius of Venus' orbit at arrival)/2. Or (152.1 * 10^9 m + 108.94 * 10^9 m)/2 = 130.52 * 10^9 m. Velocity at apoapsis: v^2 = 1.327 * 10^20 (2/152.1 * 10^9 - 1/130.52 * 10^9) v = 26985.2 m/s Velocity at periapsis: v^2 = 1.327 * 10^20 (2/108.94 * 10^9 - 1/130.52 * 10^9) v = 37676.3 m/s The velocity of the spaceship in Earth orbit can be calculated from the altitude, and the altitude is as low as possible to take maximum advantage of the Oberth effect. I'm going to guess around 200 km. v^2 = 3.986 * 10^14 (2/6578000 - 1/6578000) v = 7784.34 m/s. Up until here everything seems fine. Now we subtract the spacecraft's orbital velocity from the earth's orbital velocity: 21505.66. We subtract because we need to lose velocity. But now it seems like we have too slow an orbit even before the escape burn, which seems unlikely to me. I can't find anything that could help me here anywhere else. Any ideas on where I messed up?
  13. the steam summer sale is live

    No, but I don't think it ever goes on sale. It's worth 20$, though.
  14. the steam summer sale is live

    Alright, I just bought Bastion Gunpoint The Half-Life bundle, with 11 games. OneShot Papers, Please Please, don't touch anything and The Room For a little over 20$ USD.
  15. SpaceX Discussion Thread

    SpaceX doesn't patent anything they do.