Here is a description (
) how SpaceX rocket Falcon 9 gets the Dragon into orbit: Note that the poor rocket is under maximum stress (loads applied on it are maximum) 80 seconds after liftoff. Then it is easy and smooth travel up.
http://www.spacex.com/downloads/spacex- ... esskit.pdf
At one minute, 10 seconds after liftoff, Falcon 9 reaches supersonic speed. The vehicle will pass through the area of maximum aerodynamic pressure—max Q—10 seconds later. This is the point when mechanical stress on the rocket peaks due to a combination of the rocket’s velocity and resistance created by the Earth’s atmosphere.
Around two and a half minutes into the flight, two of the first-stage engines will shut down to reduce the rocket’s acceleration. (Its mass, of course, has been continually dropping as its propellants are being used up.) At this point, Falcon 9 is 90 kilometers (56 miles) high, traveling at 10 times the speed of sound. The remaining engines will cut off shortly after—an event known as main-engine cutoff, or MECO. Five seconds after MECO, the first and second stages will separate. Seven seconds later, the second stage’s single Merlin vacuum engine ignites to begin a six-minute, 14-second burn that brings Dragon into low-Earth orbit.
Forty seconds after second-stage ignition, Dragon’s protective nose cone, which covers Dragon’s berthing mechanism, will be jettisoned. At the nine minute, 14 second mark after launch, the second-stage engine cuts off (SECO). Thirty-five seconds later, Dragon separates from Falcon 9’s second stage and seconds later, Dragon will reach its preliminary orbit.
It then deploys its solar arrays, and begins a carefully choreographed series of Draco thruster firings to reach the space station.
So after 70 seconds the speed is 340 m/s and after 150 seconds it is 3 400 m/s, but the altitude is only 90 000 m, so the average speed has been 600 m/s ... and it seems the figures do not make sense!
It would appear that the second stage is orbiting Earth not far from the Dragon. And it will remain there! In low-Earth orbit.
Dragon will, however, soon return to Earth and drop into the Pacific ocean 450 km off southern California.
At what point during the descent will the Dragon be under peak mechanical stress? That's the question!