Talk:Sub-orbital spaceflight

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[edit] I'm confused...

So any vehicle that travels higher than 100 km yet slower than orbital speed is said to be in Sub-orbital spaceflight.

I don't understand why it is slower than orbital speed. According to the definition of the Karman line, shouldn't it be faster ? In fact, are suborbital flights such as those performed by SpaceShipOne slower or faster than orbital speed ? --Scroteau96 21:28, 25 February 2007 (UTC)

Suborbital flights are almost always slower than orbital speed. SpaceShipOne was much slower than orbital speed. If you can achieve orbital speed (which is very expensive), then you might as well inject into orbit, otherwise you have wasted a lot of money. Charles 16:09, 25 March 2007 (UTC) The only known cases of suborbital flights exceeding orbital velocities were mission failures, e.g. Pioneer-1. Nobody intentionally flies an orbital speed suborbital trajectory (i.e. nobody has money to burn).Charles 16:20, 25 March 2007 (UTC)

Has anyone done the math to show that the successful lunar impactor missions weren't on sub-orbital trajectories? Intuitively, an object impacting the face of the moon following a direct tracjectory had little angular velocity.... Sdsds 20:47, 25 March 2007 (UTC)

Earth escape missions do not fit the generally accepted defintion of suborbital. I think we are splitting hairs here Charles 03:05, 26 March 2007 (UTC)

You are right -- we're splitting hairs. Even so, a lunar impact doesn't imply an Earth escape. What matters is that this article is a great opportunity to explain a bit of orbital mechanics, and it isn't clear the article does that very well yet, given that readers describe themselves as "confused". Sdsds 03:29, 26 March 2007 (UTC)

Fair enough. Over the weekend I will try to write a few words on parabolic trajectories versus elliptical orbits, linking to other content on Wikipedia which covers it in more detail.Charles 13:33, 30 March 2007 (UTC)

[edit] Flight duration

I restored some text mentioning the duration of the Pioneer 1 sub-orbital flight (43 hours). If you can find a real-world (not theory) example with a longer duration, please use it instead. (On the theory side: if a flight exits the Hill sphere, can we agree it would be non-orbital even if tangential velocity were zero?) Sdsds 15:35, 12 March 2007 (UTC)