Comment by azernik | Hacker News Reader

Comment by azernik | Hacker News Reader

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The problem is that, no matter how cheap your fuel is, you have to build a launcher that can lift off while carrying all that fuel. It's expensive to make a pressure vessel that strong and light and large, engines that powerful, etc.

If launch gets cheap enough given current launcher sizes, you can get into in-orbit assembly, but that requires immense investment into robotics or a lot of spending to support (machine-assisted) human construction workers. i.e. you can't launch Apollo as a single package on Falcon 9s no matter how many you can afford, and if you want to send it up in multiple packages you need to either make the spacecraft bigger and bulkier and more expensive so that it's modular, or send up a few times the mass of the resulting spacecraft in assembly robots or construction workers' habitats.

(That's why Starship is so exciting even if it doesn't end up meeting Musk's cost targets, and why SLS has been so enticing for NASA despite its shitshow of a development process - putting up a single large payload in one launch is an advantage in and of itself.)

Please note that the ISS was assembled on orbit from many small components and subassemblies: the largest module was IIRC about 22 tonnes, while the ISS itself is around 420 tonnes. The Soviets pioneered this with Mir, and ISS was designed around a core that was originally intended to be Mir 2.0.

So we have quite a bit of experience assembling one big structure in orbit—a 25 year learning experience, basically, which has given us a toolbox of standards for docking adapters, compatible modules, external manipulators based on the Canadarm, and experience in on-orbit refueling and resupply.

Starship is big and (in theory) cheap, yes, but it's not obvious that we can't do this stuff with smaller and pricier tools.

Apollo didn't go for on-orbit assembly because they were in a blinding hurry (JFK set the "by the end of the decade" goal in 1961-ish) and it's taken us 25 years of plodding to get there. But we could do it now.

Most of the weight of Apollo package at the low earth orbit was fuel. Fueling in space was not considered I suppose as this was too difficult with technologies from sixties. These days it is considered possible, so launching Apollo-size package to the Moon should be possible with much smaller rockets and refueling in the orbit.

Not to toot my own horn too much on here, but I've written a fair bit about these issues going forward: http://heffern.net/rob/index.php/2018/08/25/note-1-kismayo-s...

The current NASA spending is ~$22,000/kg to get into orbit. Elon and NASA both see that getting down to ~$200/kg by 2070, only 50 years away.

When we're talking about $200/kg, the launch site's location relative to the equator will become a BIG deal. You'll see a ~4% difference in cost per kilogram (wildy estimated here) if you are more than 17 km off the equator. That means if you wnat to launch your 160kg-self more than 17km from the equator, it'll be an extra ~$1400.

For a lot of reasons that my posts explain much better, buying certain Somalian real estate is a VERY good move right now. Granted you have to be muslim to do so.

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