Crew Dragon Docks with ISS • Hacker News Board

Re: Crew Dragon Docks with ISS

#251

Post by ericol » Mon, Jun 01, 2020, 2:47 PM UTC

mortehu wrote: post #250

yellowapple wrote: post #20

Earlier quoted context omitted.

I got it on the first try, but only because I've got 600+ hours of Kerbal Space Program under my belt (where docking is much harder when you consider that docking in KSP entails actually getting to the target and doing it with imbalanced RCS thrusters that I placed on the craft willy-nilly; SpaceX's online docking sim was a breeze in comparison). Trick was to get rotation aligned first, then worry about translation.…

If you do rotation then translation, you're either going to waste fuel or time. Just aim for the target and get within 20 meters before doing any of that, and the amount of translation you'll have to do is minimal. It's like traveling on the hypotenuse instead of the other two sides of a right triangle.

Thta's an interesting point, and something I thought a lot about while I was doing this.

Basically, this simulator just cares about the physics of it, but not resources (Fuel, oxygen, etc).

I did it exactly that way, first rotation then translation. The 2nd fail it took me so long that in the 3rd (and successful) run I just hit the metal after getting the rotation correctly.

Side note, it's much easier to get the rotation right first and then moving the ship.

It was fun, thought.

Re: Crew Dragon Docks with ISS

#252

Post by yellowapple » Mon, Jun 01, 2020, 3:57 PM UTC

redis_mlc wrote: post #239

yellowapple wrote: post #221

Earlier quoted context omitted.

> Almost no science is done on the ISS. The very presence of people on the ISS is "science". The whole point of the ISS is to investigate the effects of long-term space habitation on humans. Plus, the ISS itself is an experiment, demonstrating the feasibility of in-orbit assembly of complex human-habitable structures from individually-launched-and-deployed modules (on a scale far greater than its predecessor Mir). Th…

No, the Hubble and WMAP are some of the most-cited experiments, and ISS the least. The ISS orbits at only 250 miles, barely into LEO. The wikipedia article has a long list of experiments, but the question is, "Do they actually contribute anything?" Can you name one scientific result from an ISS experiment? I can't. > the effects of long-term space habitation on humans. Humans aren't colonizing anything in space. You'…

> No, the Hubble and WMAP are some of the most-cited experiments, and ISS the least.

Just because the experiments aren't as frequently cited doesn't mean they didn't happen at all, or that they're unimportant.

> The wikipedia article has a long list of experiments, but the question is, "Do they actually contribute anything?"

This one is vital to our understanding of how space radiation affects embryonic development, which is critical for space colonization: https://www.nasa.gov/mission_pages/station/research/experime...

Or this one, which tested various fire suppressants in microgravity to determine their effectiveness, which is critical for manned spaceflight safety beyond merely the ISS: https://www.nasa.gov/mission_pages/station/research/experime...

Or this one, where the Michael J. Fox foundation partnered with NASA to conduct research on the ISS to replicate a key protein involved in Parkinson's disease (LRRK₂) in microgravity, allowing for much larger and more uniform growth patterns than possible on Earth: https://www.michaeljfox.org/news/parkinsons-protein-blasting...

Or this one, which evaluated the risks of microbial contamination on interplanetary missions (which could jeopardize the search for extraterrestrial microbes on e.g. Mars) by examining microbes that survived on the exterior of the ISS: https://pubmed.ncbi.nlm.nih.gov/22680691/

> Can you name one scientific result from an ISS experiment? I can't.

That only goes to show your lack of willingness to educate yourself on the matter. Like, a search engine ain't exactly hard to use; I was able to pull all those examples within a couple minutes.

> Humans aren't colonizing anything in space. You've read too many scifi books.

No, I've read "too many" research papers and NASA reports. Evidently you have read none.

Humans absolutely will colonize space. Obviously not right this second, but humankind has been making baby steps toward that goal for as long as it's known of the existence and the vastness of space, and there is no reason to believe that will somehow not continue to be the case. Earth won't last forever, especially at the rate we're destroying it; permanent space colonization is therefore not just an economic and scientific boon, but absolutely imperative for the long-term survival of our species.

Re: Crew Dragon Docks with ISS

#253

Post by hinkley » Mon, Jun 01, 2020, 4:51 PM UTC

matthewdgreen wrote: post #135

tomp wrote: post #126

Earlier quoted context omitted.

I’m guessing the current price has to pay for a whole new rocket, as NASA probably won’t use a used (“flight-proven”) one for humans. Eventually I expect used ones to be not only cheaper, but also more reliable. Like for (water)ships - they say “it’s new after you’ve owned it for a year”, the implication being that you spend the first year discovering and fixing manufacturing defects.

What happens to the rockets after they're flown for a single mission? Do they belong to SpaceX for later re-use in commercial cargo missions, or does NASA own them?

I think I'm picking up from context (aka reading between the lines) that the optics of NASA using a refurbished rocket - and it failing - is not good, so let SpaceX do what they want.

Recall that a lot of aerospace budget from the US is defense spending dressed up as something else. Similar to the way the original space race was a proxy war for a proxy war: If you can fly people into space you can fly an ICBM to Moscow/Washington DC.

Re: Crew Dragon Docks with ISS

#254

Post by computerex » Mon, Jun 01, 2020, 7:40 PM UTC

simonh wrote: post #172

computerex wrote: post #160

Earlier quoted context omitted.

Whilst I agree with the general sentiment, the Space Shuttle was the single most capable spacecraft that has ever flown. You are not being fair in measuring it simply on the basis of how much mass it could put in Orbit.

It was an amazing vehicle and highly capable in some way, but severely constrained in others. The main problem is it was almost completely useless for any missions or activities beyond LEO. In theory you could use it to put up a small boost stage for a light interplanetary probe, but its cargo capacity was a bit small for that, and there’s just no point using a whole shuttle to do it. Now that we have Falcon 9 and He…

The Shuttle was never designed for operations outside of LEO. It performed the role it was designed to fulfill beautifully. The reusability wager didn't pay off and the Shuttle was expensive as hell but by golly was it capable. Nothing can compare to its combination of capabilities in putting/retrieving payload, being able to service assets with RMS, and the size of the crew it could carry and provide them a relatively comfortable environment, space lab, operational freedom it provided in extending margins of errors due to OMS and aerodynamic reentries, etc.

Re: Crew Dragon Docks with ISS

#255

Post by gfodor » Tue, Jun 02, 2020, 6:18 PM UTC

pbhjpbhj wrote: post #167

helldritch wrote: post #162

Earlier quoted context omitted.

It's also worth mentioning that coming back isn't necessarily a fixed requirement. I would happily live a shorter live on Mars - with the risk overhead of being stranded in the event of a catastrophic failure - for the chance to be one of the first Martian settlers. Foreign colonists in the Americas (ignoring any political aspect of this) faced disease, starvation and attacks from natives but still colonised America…

Wasn't it more that trying things in [the continent of] America seemed more likely to yield success than staying with what they had where failure was relatively certain. Like religious persecution at home was certain for the Pilgrim Fathers, but in all likelihood they could form colonies where they could freely practice their religion by risking it in North America. For others it was abject poverty at home, or try ca…

Not how things are going. Being able to eject oneself from the political and cultural norms of Earth is becoming more and more attractive concept. All of the technology and knowledge, but, potentially, with none of the baggage.

One critical junction will be how much the Mars colony can avoid the smuggling in of bad ideas and ideologies. If done well, this could result in a radical divergence between the cultures, and wealth, of the two planets.

Re: Crew Dragon Docks with ISS

#256

Post by yellowapple » Tue, Jun 02, 2020, 7:13 PM UTC

mortehu wrote: post #250

yellowapple wrote: post #20

Earlier quoted context omitted.

I got it on the first try, but only because I've got 600+ hours of Kerbal Space Program under my belt (where docking is much harder when you consider that docking in KSP entails actually getting to the target and doing it with imbalanced RCS thrusters that I placed on the craft willy-nilly; SpaceX's online docking sim was a breeze in comparison). Trick was to get rotation aligned first, then worry about translation.…

If you do rotation then translation, you're either going to waste fuel or time. Just aim for the target and get within 20 meters before doing any of that, and the amount of translation you'll have to do is minimal. It's like traveling on the hypotenuse instead of the other two sides of a right triangle.

Rotating before translating should have little to no impact on fuel consumption. You still have to do the same amount of translation no matter how the craft is oriented. That means the same amount of energy, and thus the same amount of fuel. It took a little bit more time, but at the timeframes typical of orbital docking it's negligible.

In my first-try-success attempt, I was doing all translations at once, not something silly like lining up the numbers one at a time (that won't work well anyway, due to the differences in orbit between yourself and the docking target). That is: moving toward the ISS while simultaneously moving up/down and left/right to line up, and thus moving along the hypotenuse.

And by the way, this seems to be the exact approach Crew Dragon Endeavour took, judging by what I saw in the livestream early Sunday morning. They were already lined up rotationally before starting the final docking approach.

Re: Crew Dragon Docks with ISS

#257

Post by flingo » Wed, Jun 03, 2020, 5:56 AM UTC

yellowapple wrote: post #44

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…

> 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…

AFAIK, the ISS needs to be de-orbited over an ocean, burned up, and replaced. (like the plan was from the beginning)

There are a number of scary mould patches up there, and potentially other pathogens, with no real way to properly clean the whole thing.

Re: Crew Dragon Docks with ISS

#258

Post by stevens32 » Wed, Jun 03, 2020, 6:52 PM UTC

OctaviusCrassus wrote: post #244

stevens32 wrote: post #225

Earlier quoted context omitted.

Free market doesn't seem correct here since the government is the customer.

Govt is 100% funded from the free market

> In a free market, the laws and forces of supply and demand are free from any intervention by a government or other authority and from all forms of economic privilege, monopolies and artificial scarcities

https://en.wikipedia.org/wiki/Free_market

Re: Crew Dragon Docks with ISS

#259

Post by mortehu » Sat, Jun 06, 2020, 3:28 PM UTC

yellowapple wrote: post #256

mortehu wrote: post #250

Earlier quoted context omitted.

If you do rotation then translation, you're either going to waste fuel or time. Just aim for the target and get within 20 meters before doing any of that, and the amount of translation you'll have to do is minimal. It's like traveling on the hypotenuse instead of the other two sides of a right triangle.

Rotating before translating should have little to no impact on fuel consumption. You still have to do the same amount of translation no matter how the craft is oriented. That means the same amount of energy, and thus the same amount of fuel. It took a little bit more time, but at the timeframes typical of orbital docking it's negligible. In my first-try-success attempt, I was doing all translations at once, not somet…

Yes, you're right. You can of course travel on the hypotenuse even if you're not oriented along it. I was probably stuck in some fixed front wheel thinking. I would think it's a lot easier to get the the proportion of lateral speed exactly right if you're aimed along the hypotenuse though.

Re: Crew Dragon Docks with ISS

#260

Post by yellowapple » Sun, Jun 14, 2020, 2:28 AM UTC

mortehu wrote: post #259

yellowapple wrote: post #256

Earlier quoted context omitted.

Rotating before translating should have little to no impact on fuel consumption. You still have to do the same amount of translation no matter how the craft is oriented. That means the same amount of energy, and thus the same amount of fuel. It took a little bit more time, but at the timeframes typical of orbital docking it's negligible. In my first-try-success attempt, I was doing all translations at once, not somet…

Yes, you're right. You can of course travel on the hypotenuse even if you're not oriented along it. I was probably stuck in some fixed front wheel thinking. I would think it's a lot easier to get the the proportion of lateral speed exactly right if you're aimed along the hypotenuse though.

True. Still, if you wanted to get really exact about it, you could surely work it out mathematically (i.e. by making sure your velocity components are proportional to your distance components).

So for example, with the simulator loaded up in a tab right now, after lining up the rotation, I'm seeing:

    X | 200.0 m
    Y | 12.0 m
    Z | 30.0 m

So if I then apply an X thrust of 20 m/s, Y thrust of 1.2 m/s, and Z thrust of 3.0 m/s, then I should travel along the hypotenuse and reach the docking port in 10 seconds. Likewise, a thrust of X=2,Y=0.12,Z=0.3 would get me there in 100 seconds (and X=200,Y=12,Z=30 would get me there in an insane single second). Of course, some corrections will be necessary along the way to account for small differences between my orbit and the target orbit (which is more relevant the longer it takes for you to get to the target), and the velocity change ain't instantaneous so I'll need to adjust for that, too (making 10s or 1s runs kinda implausible with the current interface, unless perhaps I do some kind of browser-level scripting to click the buttons and read the numbers).

Crucially, this makes it feasible for a computer to do automatically (though automated docking tends to stop shy of actually docking from what I understand, instead using CanadArm to grab the craft and put it on the dock).

You're right that aiming along the hypotenuse makes this a little bit easier to eyeball, but it also makes it a bit harder in other respects since now you'll have to adjust both rotation and translation along the way to stay along that slightly-curving hypotenuse.