Crew Dragon Docks with ISS • Hacker News Board

Re: Crew Dragon Docks with ISS

#81

Post by yellowapple » Sun, May 31, 2020, 4:20 PM UTC

toyg wrote: post #53

yellowapple wrote: post #44

Earlier quoted context omitted.

> We now have the capability to put up another ISS today, resupply it, and staff it, at a fraction of the cost, all with launch equipment made by a single company that started a decade ago. This is the part that's exciting for me. Whether it comes in the form of more space stations like the ISS or a much bigger and reinvigorated ISS, either way is a vital step in the right direction toward making humanity less behold…

I love space exploration like the next guy, but I have a massive fear that a proliferation of space-stations will lead to unpleasant situations. With all its tensions, the ISS has been an amazing tool for soft diplomacy; if we start having country-specific stations we’ll soon end up with nasty arguments. Already we have competing satellites rumoured to have classified capabilities, I hate to think what they could do…

My hope would be that all (or at least most) such new space stations would be "international" space stations. Stations should be differentiated by purpose rather than nationality, I think. Space doesn't have borders.

But yeah, this is definitely a reason why I hope we can keep the ISS going and just keep building on it. Additional space stations should be for good reason (for example: orbiting the moon, or - my crazy dream scenario - one orbiting in the past-GEO graveyard orbit to collect and refurbish dead satellites).

That means we should allow China to participate in the ISS, too. There are some national security concerns, apparently, but we overcame those with the USSR/Russia, and China should be no different.

Re: Crew Dragon Docks with ISS

#82

Post by bane » Sun, May 31, 2020, 4:20 PM UTC

the_duke wrote: post #70

toyg wrote: post #53

Earlier quoted context omitted.

I love space exploration like the next guy, but I have a massive fear that a proliferation of space-stations will lead to unpleasant situations. With all its tensions, the ISS has been an amazing tool for soft diplomacy; if we start having country-specific stations we’ll soon end up with nasty arguments. Already we have competing satellites rumoured to have classified capabilities, I hate to think what they could do…

China plans to launch the first part of their own space station next year. [1] They actually wanted to join the ISS effort, but were given a firm no and had no other option than to do pursue their own. [2] I don't think we will see any other country-specific stations for a long time, but modular commercial stations that can be shared for research and potential business endeavors (hotels, specialized manufacturing, ..…

Don't forget the Tiangong program [1], which resulted in this spectacular docking and entry [2]

1 - https://en.wikipedia.org/wiki/Tiangong_program

2 - https://youtu.be/rPqJyS26e60

Re: Crew Dragon Docks with ISS

#83

Post by flixic » Sun, May 31, 2020, 4:21 PM UTC

gpm wrote: post #68

cbhl wrote: post #13

Earlier quoted context omitted.

First three times I tried doing it by eye and ended up hopelessly lost. Needed to pull out my trigonometry to figure out how to line up the capsule to get the Y/Z aligned...

There's a really simple strategy to this. One at a time move pitch, yaw, and roll to zero (with 0 velocity). Before touching any translation buttons. Never touch the pitch yaw and roll buttons again. Start moving x, y, and z translation to zero using transnational thrusters. Make sure you zero out y and z before you get close to zeroing out x.

Using this strategy docking is much, much easier than trying to follow hexagons.

Re: Crew Dragon Docks with ISS

#84

Post by IdontRememberIt » Sun, May 31, 2020, 4:23 PM UTC

hinkley wrote: post #36

I recall Elon was hoping to get an order of magnitude reduction in cost per launch, but Wikipedia claims it costs $160 million per launch versus the Soyuz price of $76 million per astronaut. That would “only” be a 3x reduction with a crew of seven, but they’ve configured for a crew of four, which is a hair under 2x. I wonder how reuse affects the math, and what they’ll be able to do to lower those prices further. Obv…

Could not find back the values. By memory (USD/kg), Soyuz is 20k, (futur launcher) ESA 5k or 8k, and SpaceX 2K. (Can someone confirm?)

Whatever the values, what are interesting are the magnitudes.

Re: Crew Dragon Docks with ISS

#85

Post by landa » Sun, May 31, 2020, 4:27 PM UTC

moftz wrote: post #50

jtdev wrote: post #11

How much AI/ML do you think is running on the software associated with this launch and docking? I suspect there’s a great deal of very explicit, well tested code, but very little AI/ML.

Very little in terms of what you would consider AI or ML. It's a lot of trig and control theory. You do a lot of the math beforehand to figure out the script the craft will follow to reach the ISS. Once it gets close, you either use manual controls or let autopilot do the docking. The autopilot is basically looking some dots on a camera and firing the thrusters to make the dots line up right. It's more like a dumb PI…

What you wrote is what I would have guessed. Are you also guessing or do you know for sure? It sounds right, but I'm very curious about the actual answer to this question.

Re: Crew Dragon Docks with ISS

#86

Post by raverbashing » Sun, May 31, 2020, 4:27 PM UTC

calaphos wrote: post #75

starik36 wrote: post #21

Earlier quoted context omitted.

All true, however, (splitting hairs, yes), the reason FH9 can best the shuttle boosters is because they had to carry the shuttle itself, which was around 50 tons.

Turns out it is a lot more useful to (potentially) reuse the first stage than to carry a lot of additional weight to reuse the last stage.

Well, but the Shuttle SRBs were reusable.

The only non-reusable part was the external fuel tank.

But yeah, sending something as big as a bus up and down was probably the bane of it.

Re: Crew Dragon Docks with ISS

#87

Post by ape4 » Sun, May 31, 2020, 4:31 PM UTC

yellowapple wrote: post #57

ape4 wrote: post #40

Watching now.. they were unable to get the "hard line" voice working. VOIP?

Considering how long the ISS has been up there, it could be POTS or something similarly-analog. Dragon→ISS was clear, but ISS→Dragon was not, making me think that maybe there's some wire or connector in the latter direction that's shoddy (and that'd be more common for analog/POTS than digital/VOIP, where such garbling would be bidirectional and/or nothing would be heard on either end). Then again, I ain't exactly a s…

Makes sense. They just fixed the hard line

Re: Crew Dragon Docks with ISS

#88

Post by walshemj » Sun, May 31, 2020, 4:32 PM UTC

hoorayimhelping wrote: post #48

cletus wrote: post #39

So when seeing this I had two questions, one of which I've found the answer to, one of which still remains a mystery. 1. Why only two astronauts? and 2. How much is Crew Dragon costing? For (1), it's stated [1] that Crew Dragon has a capacity of seven astronauts but only 4 for NASA? How does that work? Does that mean the NASA configuration only has 4 seats? I found this [2] saying seats 1 and 4 were empty. Why not 4…

> Why not 4 astronauts? You've been in the teamwork game a long time, right? You know that each new team member added to a team does something like double or quadruple communication overhead. They're trying to work out the kinks - they're going to with a small team of experienced people to stay focused. There's probably also a limit to how many people they want to keep track of on ISS, like you said. It's also less r…

Reduces risk for the first flight

Re: Crew Dragon Docks with ISS

#89

Post by VLM » Sun, May 31, 2020, 4:40 PM UTC

bane wrote: post #30

7thaccount wrote: post #22

Earlier quoted context omitted.

Incredibly impressive, but you have to take into account both more modern technology, as well as the fact that they were able to build off the shoulders of giants. It is still amazing of course, but I doubt they could've done the same thing during the era of the mercury program, so not really apples to apples comparison.

Sure, there are likely many small advantages that add up. For example, 3 flat panels and a few buttons probably weigh less than a metal panel full of dials, allowing for a better payload ratio. That technology wasn't available during the Mercury/Gemini/Shuttle period for any price.

sensors and wiring always weighed more. Of course now the wiring COULD be CANbus or similar in concept instead of individual (heavy) wires. Or move the analog processing and microcontroller to the sensor itself instead of running wires all over the place to a central computer.

Re: Crew Dragon Docks with ISS

#90

Post by trixie_ » Sun, May 31, 2020, 4:41 PM UTC

7thaccount wrote: post #22

bane wrote: post #15

SpaceX runs basically as a giant R&D program that also happens to accomplish useful things as byproducts of its approach (with the miracle of insurance to cover costs if things get explody). Every flight is data for incremental improvement. If you think of all SpaceX has ever done was try to get to this point, with somewhere around 80 flights on the Falcon 9, but for a variety of mission buyers (NASA, USAF, Commercia…

Incredibly impressive, but you have to take into account both more modern technology, as well as the fact that they were able to build off the shoulders of giants. It is still amazing of course, but I doubt they could've done the same thing during the era of the mercury program, so not really apples to apples comparison.

Maybe not during Mercury, but definitely during the 70s all the technology was there to build a cheap, reusable rocket and capsule.

The dream was that the shuttle could be that system, but it did not turn out that way. And giving in to the 'sunk cost fallacy' they supported the shuttle for the next 40 years.

Arguably you could say we are 50 years behind where we should be. Unfortunately driving down costs is probably the hardest thing for any government organization to do. Given that there is no competition, no shareholders, no profit motive etc..