I think at the scale of spacelift required to maintain a colony on Mars, the weight efficiency of the asteonauts would be less than a rounding error.
Maintaining a colony on Mars indefinitely will require the transport of millions of tons of material. It’s one thing to plonk down a temporary lander that takes off in a few weeks. If that"s what you are doing, lighter astronauts with lower food/air requirements might make a difference. Maybe that’s the context in qhich Zubrin was speaking?
But if we want permanent habitats, they require a constant flow of spare parts, machinery will need replacing periodicaly, and expansion means always bringing in more infrastructure. There are plenty of consumables that aren’t food. And the habitats themselves have to be sturdier and will weigh quite a bit.
The only way we can even come close to being able to do it financially is if Musk’s dream of a $2 million Starship flight becomes a reality and hundreds of them are flying all the time. Even then, it would be difficult.
Its not just human weight. It’s everything. You need 50% larger oxygen generators. 50% more heating/cooling capacity. 50% more food and water, and thus 50% larger farms and water recyclers. 50% heavier exercise equipment. 50% sturdier chairs. 30% more clothing material. 30% larger beds. It all scales–maybe not a full 50%, but somewhere in the vicinity (actually, a chair probably scales >50%).
A 10 t payload may be a rounding error compared to a 1000 t rocket, but for the same performance, a 15 t payload requires a 1500 t rocket, and that isn’t a rounding error.
Of course, when you get millions of people, you can’t be that selective. And maybe you want some people on the large end of the spectrum just to do jobs that smaller people can’t. But for something like a research outpost, you want as many human brains as possible.
I suppose one could start with the height/weight limits for USAF pilots or NASA’s astronaut corp. Apparently lower limits are as important as upper: one has to be able to reach controls from a sitting position for example.
So we’re talking about 3ft high humans? I kind of assumed that we were talking about someone 5’3" and 100 lbs vs 5’10" and 170 lbs. i.e. selecting astronauts in part based on being on the small side of normal.
The way things are going, it will be neither. The first humans will bring with them a few hundred androids to build stuff, and you don’t need to feed them anything.
A 170 lb person has roughly 1.7x the metabolic needs as a 100 lb person. That’s 70% more food, water, and O2. Something like a chair needs 70% greater strength in the structural members–and has to be a few inches higher if it’s going to be comfortable for the “average” person, so it works out to be >70%. Surface area scales more like W^\frac{2}{3}, so things like clothing mass will scale a bit less, but that’s still significant.
Why? All of this stuff scales exactly with metabolism. Eat twice much of the same food and you need twice as much O2 and water.
Food requirements aren’t perfectly linear, but they’re close. The brain takes more energy than its mass-share, but it’s still only around 20%. The rest of your energy input goes into maintaining your fat and muscle stores (along with thermoregulation and some other things). All of this goes up linearly with weight.
And even aside from all that, big people need more stuff. I came to a funny realization a while back when traveling with a friend. He’s almost twice the weight as I am (maybe 220 lbs vs. 125). We were kinda wondering how I manage to pack a full set of clothes into a backpack, while he needed a suitcase. Hadn’t considered it previously, but all of his clothing is also nearly 2x as massive, whereas a “normal” sized backpack doesn’t scale, so my clothes fit easily while his would not.
Small people really do use far less resources. I sometimes hear people complain that cars like the Model 3 are uncomfortably small. Not for me! In fact I’d prefer an even smaller car. Some 6’ guy needs a large SUV to feel comfortable, while I just need a small sedan.
The idea of getting on Musk’s spaceship gives me the exact same creeps as the idea of riding that homemade sub to the Titanic. Guess I’m not very adventurous.
Despite the claims of a thousand dipshit news editors, it is not “Musk’s spaceship.” It’s SpaceX’s spaceship. And SpaceX has demonstrably the highest reliability rocket in existence. It lands more reliably than most rockets launch, despite that being a more challenging problem. Crew Dragon has not launched quite enough to prove that it’s the most reliable crew launcher (though it has a 100% success rate right now), but it’s getting there.
Obviously no one should be riding on Starship right now. SpaceX themselves (Gwynne Shotwell specifically) say that they will probably have to launch a hundred or so times before they put crew on it. This probably won’t take more than a handful of years.
There’s only one Earth-launched crew flight that we know of yet: the Dear Moon mission. But it has no fixed timeframe and won’t launch until both SpaceX and the participants are comfortable.
As for non-crew missions, there will be many, many Starlink flights among them. Those alone will prove out the reliability. I don’t know if any others have paid for flights yet, but these tend to be fairly secretive anyway. I’m sure they’ll come once Starship has a few full orbital missions under its belt (even if recovery and reentry are not yet solved problems, since they’re irrelevant to the payload).
Yep. Getting customers to pay for the Falcon 9 landing development program was a great move. The customers don’t care what happens when the booster is disposed of. So use that part as a test flight. And when it came to actual reuse, customers were hesitant at first, but with a discount they came along. After a while they stopped getting a discount.
I suspect Starship has a few contracts that we don’t know about. But they might be contingent on some level of demonstrated performance. But even if not, Starlink will prove things out fairly rapidly.
And even if the launch is the unreliable part, for unmanned launches, it’s a simple economic calculation. If having a payload in orbit will give your company a billion dollars in profit, and the launch has a 50% chance of success, then any cost of launch that’s less than $500 million is worth it.
That’s especially true for something like Starlink, where you’re going to need a whole bunch of launches anyway, so the risk can be smeared out over the whole program.
I watched the whole thing. The guy is an ass, was totally unprepared (didn’t know basic facts about the system), and basically was looking for things to snark about because he doesn’t like Elon Musk. In the end he had to admit that it was impressive.
His criticism of Hyperloop got him a lot of viewers, and since then he’s been trying to attack all things Musk, warranted or not.
