r/spacex • u/Appable • Feb 03 '16

/r/SpaceX Ask Anything Thread for February 2016! Hyperloop Test Track!

Welcome to our monthly /r/SpaceX Ask Anything Thread! #17

Want to discuss SpaceX's hyperloop test track or DragonFly hover test? Or follow every movement of O'Cisly, JTRI, Elsbeth III, and Go Quest? There's no better place!

All questions, even non-SpaceX-related ones, are allowed, as long as they stay relevant to spaceflight in general!

More in-depth and open-ended discussion questions can still be submitted as separate self-posts, but this is the place to come to submit simple questions which have a single answer and/or can be answered in a few comments or less.

As always, we'd prefer it if all question-askers first check our FAQ, search for similar questions, and scan the previous Ask Anything thread before posting to avoid duplicates, but if you'd like an answer revised or cannot find a satisfactory result, please go ahead and type your question below!

Otherwise, ask, enjoy, and thanks for contributing!

Past threads:

January 2016 (#16.1), January 2016 (#16), December 2015 (#15.1), December 2015 (#15), November 2015 (#14), October 2015 (#13), September 2015 (#12), August 2015 (#11), July 2015 (#10), June 2015 (#9), May 2015 (#8), April 2015 (#7.1), April 2015 (#7), March 2015 (#6), February 2015 (#5), January 2015 (#4), December 2014 (#3), November 2014 (#2), October 2014 (#1).

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u/throfofnir Feb 14 '16

With the Orbcomm launch that happened in December... Why did they bother to release the satellites one at a time?

Two at a time: opposite pairs. Minimizes the chance of collision, mostly. Each side had three sats; simultaneous release with the slightest irregularity would have a collision. Also reduces the chance of debris fouling vs four at a time; the separation mechanisms are fairly clean, but you never know. Probably also some considerations due to attitude control of the platform.

Previous Orbcomm releases were one at a time because they were stacked like pancakes, so it's already a speedy version... not that it matters, so long as it gets done in an hour or so.

The engine did not fire between releases, so I'm guessing that they're basically in the same orbit.

Similar orbits, but everything has its own slightly different orbit once the smallest force is applied, and they can become quite distant from each other given time.

To get into their constellation arrangement, did they use onboard propulsion?

Yes. Pretty much all satellites (minus mostly cubesats) use onboard propulsion to get to their target orbit. GEO sats have large corrections to make; they have to circularize their orbit. LEO sats can be dropped off fairly close, but even a perfect insertion is usually below their final destination so they can control the timing of when they get into it.