Elon Musk’s plan to build one Starship a week and settle Mars • Hacker News Board

Re: Elon Musk’s plan to build one Starship a week and settle Mars

#91

Post by derekp7 » Thu, Mar 05, 2020, 3:38 PM UTC

KineticLensman wrote: post #55

aphextron wrote: post #48

Earlier quoted context omitted.

>Why does it need to be super-large? To simulate gravity? Rocket efficiency scales infinitely with size.

The rocket equation [0] disagrees: "In what has been called 'the tyranny of the rocket equation', there is a limit to the amount of payload that the rocket can carry, as higher amounts of propellant increment the overall weight, and thus also increase the fuel consumption" [0] https://en.wikipedia.org/wiki/Tsiolkovsky_rocket_equation

I'm having a mental blockage on this, as you can always launch 10 rockets at the same time and get 10 times the payload. Having those 10 rockets strapped together should not change the payload of them flying independently.

What am I missing here -- I'm sure I'm overlooking something.

Re: Elon Musk’s plan to build one Starship a week and settle Mars

#92

Post by Miraste » Thu, Mar 05, 2020, 3:39 PM UTC

addisonl wrote: post #60

ajnin wrote: post #45

Earlier quoted context omitted.

No, not in aerospace. The common approach is to spend years designing, simulating, and then actual tests come at the very end, and sometimes you don't even test because you can't or it would be too expensive. That's what Boeing are doing with their own rockets; Mars missions until now didn't really go through an iterative process; satellites are usually manufactured only by one and they better work once in orbit.

> years designing, simulating So trial and error, but virtually. You're telling me we went to the moon on the first try? We went into space on the first try? The Wright brothers were successful on their first flight? No, it was all trial and error.

Simulation is not the same as trial and error. There's no such thing as a perfect simulation, and imperfect simulations without real world testing and iteration result in disasters. There are many examples, but the Mars probe that crashed because of a unit conversion error comes to mind.

Re: Elon Musk’s plan to build one Starship a week and settle Mars

#93

Post by SEJeff » Thu, Mar 05, 2020, 3:40 PM UTC

jcims wrote: post #63

petewailes wrote: post #40

Earlier quoted context omitted.

Tonnage. If you're wanting to move 7/8 figure tonnage loads over a period of time, you're going to need a big trunk. In space vehicles, that means everything gets really, really big.

https://en.wikipedia.org/wiki/Payload_fraction Launch vehicles tend to scale payload capacity at a greater rate than dry mass. So a small launch vehicle like RocketLab's Electron might have a wet mass of 12,000kg at launch and an LEO payload capacity of 225kg (225/12000 ~ 1.8% payload), the SpaceX Falcon9 has a wet mass of 550,000kg and an LEO payload capacity of 22,800kg (22800/550000 ~ 4.1% payload). This just tend…

A Falcon 9 has a LEO payload capacity of 22,800kg in expendable mode, something SpaceX does not like to do. The largest payload mass they've carried to LEO was Starlink-2 at approximately 15,600kg (60 satellites at 227 kg each).

Re: Elon Musk’s plan to build one Starship a week and settle Mars

#94

Post by [deleted] » Thu, Mar 05, 2020, 3:40 PM UTC

KineticLensman wrote: post #55

aphextron wrote: post #48

Earlier quoted context omitted.

>Why does it need to be super-large? To simulate gravity? Rocket efficiency scales infinitely with size.

The rocket equation [0] disagrees: "In what has been called 'the tyranny of the rocket equation', there is a limit to the amount of payload that the rocket can carry, as higher amounts of propellant increment the overall weight, and thus also increase the fuel consumption" [0] https://en.wikipedia.org/wiki/Tsiolkovsky_rocket_equation

[deleted]

Re: Elon Musk’s plan to build one Starship a week and settle Mars

#95

Post by brlewis » Thu, Mar 05, 2020, 3:41 PM UTC

mdorazio wrote: post #35

bryanlarsen wrote: post #9

Earlier quoted context omitted.

I assume that an "all-hands" meeting at 1AM means an all-hands for everybody working the night shift, not the entire staff. Yes, shift work sucks, but that doesn't necessarily mean overwork.

Having several SpaceX employees in my circle of friends, I would not assume that at all.

Are your friends up at 1am because they're excited about what they're doing?

Re: Elon Musk’s plan to build one Starship a week and settle Mars

#96

Post by brlewis » Thu, Mar 05, 2020, 3:42 PM UTC

virgilp wrote: post #11

justapassenger wrote: post #4

Is it me, or does this article basically romanticize abusing workers and glorifies running projects without a plan, just with a goal?

AFAIK they work in shifts, non-stop; crazy hours & weekend is irrelevant in this context.

This part of the article is about shifts for assembly workers:

So Musk is making the machine to make the machine. Musk has brought lessons learned from Tesla’s assembly line so workers do not burn out. They will work three 12-hour days and then have a four-day weekend. Then they’ll work four 12-hour shifts with a three-day weekend. Thus, with four shifts, the Boca Chica site can operate at full capacity 24 hours a day, seven days a week. SpaceX is throwing in hot meals every three to four hours, for free.

Re: Elon Musk’s plan to build one Starship a week and settle Mars

#97

Post by FeepingCreature » Thu, Mar 05, 2020, 3:42 PM UTC

derekp7 wrote: post #91

KineticLensman wrote: post #55

Earlier quoted context omitted.

The rocket equation [0] disagrees: "In what has been called 'the tyranny of the rocket equation', there is a limit to the amount of payload that the rocket can carry, as higher amounts of propellant increment the overall weight, and thus also increase the fuel consumption" [0] https://en.wikipedia.org/wiki/Tsiolkovsky_rocket_equation

I'm having a mental blockage on this, as you can always launch 10 rockets at the same time and get 10 times the payload. Having those 10 rockets strapped together should not change the payload of them flying independently. What am I missing here -- I'm sure I'm overlooking something.

Correct. You can (super¹)linearly increase launch mass by adding fuel. The rocket equation hits when you're trying to go farther, rather than more massive.

¹ Superlinear because tank mass scales with a lower exponent than tank volume.

Re: Elon Musk’s plan to build one Starship a week and settle Mars

#98

Post by 101404 » Thu, Mar 05, 2020, 3:44 PM UTC

aguyfromnb wrote: post #88

peeters wrote: post #74

Earlier quoted context omitted.

I'm not in that area, but I struggle to find an analogue of a large pressurized tank on Earth where mass is the dominant cost factor. You might have equally big tanks on Earth, under equal pressures, but it will be more cost-effective to just increase the material used on the shell of the tank to solve your problems. Whereas in space, every kg that can theoretically be removed from the launch vehicle is worth investi…

> So yes it seems reasonable to me that these are groundbreaking challenges. Isn't weld strength something engineers would know/understand in advance, though? How would it come as a surprise that the welds would fail under pressure? It seems strange to me that Musk could be spending so much time working on Starship, and somehow a "badly designed, badly built, and badly checked" rocket makes it to the platform and exp…

They are currently not primarily working on the rocket, but in the production process.

Re: Elon Musk’s plan to build one Starship a week and settle Mars

#99

Post by StaticRedux » Thu, Mar 05, 2020, 3:45 PM UTC

grecy wrote: post #80

throwaway13337 wrote: post #23

It's quite inspiring to see a real goal and drive towards it. Purpose is so hard to come by now because we all don't know what we want. When we do know, we're constantly unsure about it. Such a clear goal makes it easy to have greater purpose that you don't second guess. This isn't a scheme to get rich, a zero sum political movement, or a narcissistic artistic endeavor. It's pretty unique there. There's that whole da…

> Purpose is so hard to come by now because we all don't know what we want. When we do know, we're constantly unsure about it. This statement resonates deeply with me. Whenever I meet someone new or that I might be interested in dating I ask "What are you doing with your life?" or "What are you striving for?" and I find the extreme majority of people don't have an answer beyond "I just go to a job I don't really like…

Why do they have to? I have that drive, but my wife is perfectly happy with a calm, comfortable, stress-free life. And in fact it helps to bring me back down to Earth sometimes also.

There's nothing wrong with wanting a life that free. In fact it's oftentimes admirable. Especially at times when I'm wound so tight I feel like I could pop.

If you're choosing a partner based solely on whether they want to be the next Elon Musk or not, you're doing yourself a serious disservice.

And if you really ask those questions to every potential date, you should stop, because dude, wtf?

Re: Elon Musk’s plan to build one Starship a week and settle Mars

#100

Post by pjc50 » Thu, Mar 05, 2020, 3:46 PM UTC

So we've accepted that we're never going to find life on Mars, and that there's no concern of "contamination"? Or is this just a big plan to build a city in the first bit of "unspoilt" wilderness we can find off planet?