First SpaceX launch to supply Space Station is next Sunday | Hacker News Reader

First SpaceX launch to supply Space Station is next Sunday

nasa.gov

141 pointsanigbrowl13 comments

The previous Dragon cargo flight this year was a demonstration flight, this one is the first operational resupply mission.

Also relevant, the Cygnus spacecraft from Orbital Sciences Corp. is another ISS commercial resupply vehicle and is set to have its first demonstration mission soon (in early 2013). However, unlike the Dragon the Cygnus isn't designed around a manned capsule system and it burns up on reentry.

"I would like to die on Mars," Elon Musk says, "Just not on impact." [1]

Many HN readers may already know, but pay attention to SpaceX. There's nobody even close to what they're doing, and they aren't slowing down.

[1] http://www.businessweek.com/printer/articles/71446-elon-musk...

It's about time we get a launch window before midnight on the East coast.

The entire concept of an instantaneous launch window is pretty wild.

Can anyone tell why they're having instantaneous launch windows? AFAIR when NASA was flying Shuttles, the window had a significant size.

It was discussed during the webcast of the last launch, they said to save fuel. Presumably there's a more technical discussion around it, but that seems to be the gist of it.

http://www.youtube.com/watch?v=y_4-TOcVegM&feature=playe...

The Shuttle probably had similar launch windows for docking with the ISS. You need to match both the speed and position of the ISS to dock with it.

The ISS is moving at 7.7 km every second; if you miss by 10 seconds, you would need to (roughly) drop your orbit by 10km, wait 3.6 hours, then climb back up that 10km to make up for it.

Matching position is even harder. The ISS isn't equatorial. It swings north and south of the equator in a sinusoid.

It's probably possible to have a computer or pilot dynamically respond to all these things to make up for them. But easier to just deal with it by waiting a few days.

Does anyone know if this will be an arm capture again or if it will it get to dock directly this time?

Arm capture for this round. A direct docking may be an option for later flights, and is planned for manned flights.

What are the advantages/disadvantages of each method?

Less risk with an arm capture.

With an arm capture they manoeuvre the craft a safe distance from the ISS then check it can hold position and move slowly toward/away. When they're satisfied then they edge it close enough to capture with the arm.

If it docks itself then you have to trust there won't be some weird last-minute f*ckup causing it to crash into the station.

So why not always do an arm capture?

One way of answering your question is that the ISS already has automated resupply missions: http://en.wikipedia.org/wiki/Automated_Transfer_Vehicle

Secondarily, the limited time & manpower on the station makes streamlining a resupply mission good sense - as long as there aren't huge risks.

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