Orbiter reentry

[G'th]

So in my recent visit to Kennedy, I found myself pretty fascinated by a picture they had up in the Atlantis building. Specifically, it was this picture of Atlantis during (probably after) reentry on its final mission.

Now, this piqued my interest, because if that trail is to be believed, then it would seem like the orbiter drops almost straight down for reentry, which doesn't seem right. Not only does it seem confusing as to how that would allow the orbiter to actually gain any horizontal speed at all (and thus be able to glide), but it also seems like it'd be a lot more dangerous than the way I presumed reentry was performed.

So whats the skinny here? Did Atlantis really drop straight down like that, or is that trail not what reentry would have looked like?

[cpast]

I think you're looking at the trajectory the wrong way around. The really bright part (and the sudden edge) is at the top of the picture; that's probably the Orbiter, which has gone from the bottom of this picture to the top. The shape of the trajectory on the picture is then more a function of perspective than anything else.

[BagelRabbit]

Keep in mind that since Atlantis is coming almost directly "towards" the craft that took the picture, its angle of reentry appears to be much steeper than it really is.

The Shuttles had enough fuel left after making orbit to knock a few hundred m/s off their orbital velocity, but not nearly enough to fall straight down, which would require much, much, much more Delta-V. Imaging a Kerbin orbit with the apoapsis at 100 km and the periapsis at 10km or so. This is about the eccentricity that the Shuttle's path had returning from orbit.

Interestingly, the Shuttle actually came into the atmosphere at an angle far lower than its actual glideslope at landing. It then went into a steeper dive after burning off much of its velocity, only to pull up immediately before landing to lower its vertical velocity to near-zero.

[G'th]

The more and more I look at it, is it that the trail isn't actually going straight down but just looks like it because there's no reference next to it? It seems to me now that that trail follows its orbit rather than a path back into the atmosphere.

So the picture would likely make more sense flipped 90 degrees counterclockwise.

[peadar1987]

The more and more I look at it' date=' is it that the trail isn't actually going straight down but just looks like it because there's no reference next to it? It seems to me now that that trail follows its orbit rather than a path back into the atmosphere.

So the picture would likely make more sense flipped 90 degrees counterclockwise.[/quote']

Yep, with the orbiter going from right to left.

[PakledHostage]

Keep in mind that since Atlantis is coming almost directly "towards" the craft that took the picture, its angle of reentry appears to be much steeper than it really is.

I think you must mean it is going away from the camera? The bright bit near the top of the image is almost certainly Atlantis engulfed in plasma as it re-enters while the trail extending towards the bottom of the image is Atlantis's descent path up to the time of the photo.

Also, space shuttles would re-enter in a rolled attitude to steepen their trajectory (i.e. the wing's lift was directed sideways not up). The roll would result in a cross-track velocity component but roll reversal maneuvers were used to "sway" the re-entry trajectory back and forth across the target landing site.

[Mr Shifty]

Also, space shuttles would re-enter in a rolled attitude to steepen their trajectory (i.e. the wing's lift was directed sideways not up). The roll would result in a cross-track velocity component but roll reversal maneuvers were used to "sway" the re-entry trajectory back and forth across the target landing site.

Yeah, I'd agree that it looks like Atlantis is in the middle of an S-curve there; it's veered to the left. Keep in mind that the rolls were quite steep: up to 80° to either side. And with a 40° angle of attack, that generated significant trajectory curve, as you can see.