Reading through the Wikipedia article about Gravity Turn, specifically the Use in spaceflight section, it seems that the Gravity Turn was not used in early spaceflight. Is that correct? For example, did the Vostok/Voskhod and Mercury missions make use of Gravity Turns during ascent?

Did "they" instead go straight up, then turn and accelerate? Since when are Gravity Turns common?

up vote 5 down vote accepted

That section of the Wikipedia article is very poorly written, conflating interplanetary gravity assist in one case with gravity turns (prior to my ruthless edit), and should be in no way considered comprehensive, nor as a serious indication that gravity turns weren't used prior to Apollo.

The early crewed missions (Vostok and Mercury) were flown on launchers that were based on ICBMs, which needed to achieve long downrange distances to perform their missions. Given that the ballistic and aerodynamic factors influencing rocket trajectories were well understood, there's no reason that gravity turns wouldn't have been used.

The timeline for Glenn's Mercury-Atlas 6 flight indicates that an 0.5 degree per second pitch program was flown starting at 16 seconds into the flight -- possibly not exactly a zero-AoA gravity turn, but necessarily pretty close to it; Atlas was a very fast launcher, so would have encountered very high atmospheric forces, and a significant angle of attack would have destroyed the fragile vehicle.

Here is a plot of flight path angle versus time, from NASA's performance analysis of Carpenter's Mercury-Atlas 7 flight, showing the abrupt initiation of pitchover from 90 degrees starting at about 0:15:

enter image description here

No successful orbital launcher, to my knowledge, has ever gone up to altitude and then turned; it was well known that this was inefficient long before orbital launch was possible.

  • Thanks for the Wikipedia edit as well, I was confused by the gravity assist entry you removed when I first read it. – DarkDust Sep 20 at 7:09
  • The original wikipedia article author deliberately included gravity assists 11 years ago, seeming based on a 1964 NASA paper which used the term in that way. It was questioned in the pages talk in 2009. – JCRM Sep 21 at 12:18

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