SpaceX CRS-6 Launch Webcast • Hacker News Board

Re: SpaceX CRS-6 Launch Webcast

#61

Post by mikeash » Mon, Apr 13, 2015, 9:08 PM UTC

cryptoz wrote: post #47

ceejayoz wrote: post #45

Earlier quoted context omitted.

> Could they have planned for this earlier and not got everything ready? Probably not. They were a go up until just three minutes before launch. I doubt any extant or near-future forecasting system is able to tell you that a specific storm cell will be in a specific spot at an exact minute all that far in advance.

> I doubt any extant or near-future forecasting system is able to tell you that a specific storm cell will be in a specific spot at an exact minute all that far in advance. Well, this is exactly my plan, and I'm going to do it ASAP. Prototype should be done by summer. There are millions of little weather stations all over Florida that nobody is using (smartphones). By connecting those stations together and pulling th…

How accurate would it be? Even if you can predict with, say, 95% accuracy that a thunderstorm will cause a launch scrub, SpaceX might want to give it a try anyway in case that 5% comes true. They want to launch ASAP, and they'd look dumb if they called it off only to find that the weather was fine.

Accurate forecasts are no doubt extremely valuable in many cases, but for this specific case I don't see it changing much.

Re: SpaceX CRS-6 Launch Webcast

#62

Post by baggers » Mon, Apr 13, 2015, 9:30 PM UTC

Laremere wrote: post #28

nacs wrote: post #16

"Hold. Hold. Hold. Weather is no go" @ 4:31pm EST

Specifically, there's thunderheads within their no-go radius, so weather called hold. Since it's only a 1 second launch window, there won't be a launch today. Edit: Next launch window is tomorrow at 4:10pm eastern time. However the weather outlook isn't much better.

http://en.wikipedia.org/wiki/Launch_commit_criteria#Falcon_9 within 19 kilometres (10 nmi) of an attached thunderstorm anvil cloud.

Re: SpaceX CRS-6 Launch Webcast

#63

Post by swhitt » Mon, Apr 13, 2015, 9:40 PM UTC

Laremere wrote: post #28

nacs wrote: post #16

"Hold. Hold. Hold. Weather is no go" @ 4:31pm EST

Specifically, there's thunderheads within their no-go radius, so weather called hold. Since it's only a 1 second launch window, there won't be a launch today. Edit: Next launch window is tomorrow at 4:10pm eastern time. However the weather outlook isn't much better.

> 1 second launch window

Why is it so precise?

Re: SpaceX CRS-6 Launch Webcast

#64

Post by sandstrom » Mon, Apr 13, 2015, 9:48 PM UTC

th0br0 wrote: post #55

ceejayoz wrote: post #45

Earlier quoted context omitted.

> Could they have planned for this earlier and not got everything ready? Probably not. They were a go up until just three minutes before launch. I doubt any extant or near-future forecasting system is able to tell you that a specific storm cell will be in a specific spot at an exact minute all that far in advance.

To cryptoz (can't reply, probably too deep?): I was going to argue that it would be terrible difficult to build up that smartphone network. But then I saw that you do PressureNet (awesome tool btw!) and, oh well... looks like you've definitely got the network part done already. OTOH, why not just ping @elonmusk on twitter?

preassurenet is cool!

It always reminds me about this interchange: https://news.ycombinator.com/item?id=8292091

Probably easier to google up someone on the launch team and ask them.

Re: SpaceX CRS-6 Launch Webcast

#65

Post by JshWright » Mon, Apr 13, 2015, 9:56 PM UTC

swhitt wrote: post #63

Laremere wrote: post #28

Earlier quoted context omitted.

Specifically, there's thunderheads within their no-go radius, so weather called hold. Since it's only a 1 second launch window, there won't be a launch today. Edit: Next launch window is tomorrow at 4:10pm eastern time. However the weather outlook isn't much better.

> 1 second launch window Why is it so precise?

They need to launch when the orbital plane of the station is directly overhead. The earth rotates surprisingly quickly, so even a minute or two later the plane of Dragon's orbit would be far enough off from the plane of the station that a couple expensive inclination change maneuvers would be necessary to line them up again.

Re: SpaceX CRS-6 Launch Webcast

#66

Post by trose » Mon, Apr 13, 2015, 10:02 PM UTC

swhitt wrote: post #63

Laremere wrote: post #28

Earlier quoted context omitted.

Specifically, there's thunderheads within their no-go radius, so weather called hold. Since it's only a 1 second launch window, there won't be a launch today. Edit: Next launch window is tomorrow at 4:10pm eastern time. However the weather outlook isn't much better.

> 1 second launch window Why is it so precise?

While it's possible to inject the dragon capsule anywhere and get it's orbit in line with the ISS, its much more economical to inject it really close to the ISS so they dont need to do as much work to finish the trip.

Re: SpaceX CRS-6 Launch Webcast

#67

Post by rgbrenner » Mon, Apr 13, 2015, 10:35 PM UTC

JshWright wrote: post #65

swhitt wrote: post #63

Earlier quoted context omitted.

> 1 second launch window Why is it so precise?

They need to launch when the orbital plane of the station is directly overhead. The earth rotates surprisingly quickly, so even a minute or two later the plane of Dragon's orbit would be far enough off from the plane of the station that a couple expensive inclination change maneuvers would be necessary to line them up again.

The earth rotates surprisingly quickly

Not so much the earth as ISS.

The earth rotates at 24900mi/day or about 1040mph.

The ISS, to maintain its orbit, travels at 17150mph or about 5 miles per second.

So in two minutes, it travels about 600 miles.

Re: SpaceX CRS-6 Launch Webcast

#68

Post by cryptoz » Mon, Apr 13, 2015, 10:41 PM UTC

th0br0 wrote: post #55

ceejayoz wrote: post #45

Earlier quoted context omitted.

> Could they have planned for this earlier and not got everything ready? Probably not. They were a go up until just three minutes before launch. I doubt any extant or near-future forecasting system is able to tell you that a specific storm cell will be in a specific spot at an exact minute all that far in advance.

To cryptoz (can't reply, probably too deep?): I was going to argue that it would be terrible difficult to build up that smartphone network. But then I saw that you do PressureNet (awesome tool btw!) and, oh well... looks like you've definitely got the network part done already. OTOH, why not just ping @elonmusk on twitter?

Well thanks! But actually, building the network is indeed a big challenge. We've spent the better part of our 3 years just thinking and implementing methods to do it. We've arrived at an SDK model [1] where we work with app partners to integrate simple sensor code and contribute to our network. So we're able to grow quite quickly compared to a single app to download, but it's still not easy getting the necessary scale. We're aiming for about 10 million sensors, currently have 0.5 million. So we're getting there.

I've sent @elonmusk a few messages over the years but no replies so far. I am @vallesmarineris, so I think one day he'll notice that I already live on Mars and we'll chat.

[1]: https://github.com/Cbsoftware/pressureNET-SDK

Re: SpaceX CRS-6 Launch Webcast

#69

Post by ohazi » Mon, Apr 13, 2015, 10:50 PM UTC

rgbrenner wrote: post #67

JshWright wrote: post #65

Earlier quoted context omitted.

They need to launch when the orbital plane of the station is directly overhead. The earth rotates surprisingly quickly, so even a minute or two later the plane of Dragon's orbit would be far enough off from the plane of the station that a couple expensive inclination change maneuvers would be necessary to line them up again.

The earth rotates surprisingly quickly Not so much the earth as ISS. The earth rotates at 24900mi/day or about 1040mph. The ISS, to maintain its orbit, travels at 17150mph or about 5 miles per second. So in two minutes, it travels about 600 miles.

Yeah, but the window is short because you have to catch the orbital plane, not the ISS itself. Earth's rotation speed is the relevant number here for figuring out how fast that plane sweeps across the sky.

Re: SpaceX CRS-6 Launch Webcast

#70

Post by ceejayoz » Tue, Apr 14, 2015, 12:46 PM UTC

MichaelGG wrote: post #57

cryptoz wrote: post #47

Earlier quoted context omitted.

> I doubt any extant or near-future forecasting system is able to tell you that a specific storm cell will be in a specific spot at an exact minute all that far in advance. Well, this is exactly my plan, and I'm going to do it ASAP. Prototype should be done by summer. There are millions of little weather stations all over Florida that nobody is using (smartphones). By connecting those stations together and pulling th…

What do cell phones have that are particularly useful to detect lightning? Or look at other sources for lightning, then thousands of barometers to predict movement?

Cell phones aren't needed to detect lightning. It's the pressure measurements that are potentially valuable in making a more accurate map than can be gathered by scattered weather stations.

http://www.lightningmaps.org/realtime shows lightning in realtime as they're detected by stations across the planet. If you turn on the "stations" display, you can see detectors in Utah spotting lightning in the Gulf of Mexico.