14 Oct 2020,
being the first to use a new “ultrafast” rendezvous” scheme with the ISS. Following a flawless ascent to the correct orbit, Soyuz 2.1a , Soyuz MS-17 caught up with the orbiting laboratory in only two orbits (three hours), halving the time it takes for crew to get to the Station.
The three space travelers of the Soyuz MS-17 mission launched on a six-month mission the International Space Station.
previous 3/4 orbit rendezvous:
Soyuz MS-16 4 orbit rendezvous
A three-orbit profile was deemed possible without major flight design changes after inauguration of the Soyuz 2-1A rocket that provides a much higher orbit injection accuracy than its predecessors and would allow the two correction maneuvers on Orbit #2 to be eliminated while the Automated Rendezvous Phase would still remain untouched. The deletion of the Orbit #2 maneuvers was expected to slightly tighten the already restrictive phase angle window from and upper limit of 30-35° to 25-28°.
Two-Orbit Rendezvous Profile –
To realize a two-orbit launch-to-docking profile, one would either have to deal with a very narrow phase angle range or take a different approach to find a compromise between planar and phase angle constraints. The method chosen by the Russian flight dynamics team is referred to as a Quasi-Coplanar Insertion and will broaden the planar launch window and so allow the chaser to be launched into an orbit with optimized phase angle while keeping the planar separation within a manageable range.
The second important trick that comes into play is a change in orbital inclination which can be varied in order to reduce the angle at which the orbit of the Space Station and the chaser intersect and so reduce the change in velocity required by the chaser to accomplish the plane change into the ISS orbit. Without this exploitation of orbital mechanics, the two-orbit profile was found to come with excessive propellant consumption and would not have been practical.
Setting the Inter-Orbit Angle via Inclination Modification
If accepting a 0.65° angular separation in RAAN (Right Ascension of Ascending Node), the planar launch window will broaden by ±2.5 minutes, allowing some leeway in the setup of the phase angle by the Space Station. But as consequence, the angle at which the ISS orbit and that of Progress/Soyuz intersect will be 0.51° and it would cost the spacecraft over 66m/s of delta-v to accomplish the plane change. Varying the orbital inclination by ±0.18° will allow Soyuz to accomplish the plane change at a much more manageable delta-v of 25m/s.
Widening the planar window to ±5 minutes (corresponding to phase angles of 20°) will require an inclination change of ±0.35° and a delta-v of 50m/s for the plane change, still manageable for the Soyuz/Progress vehicle within its typical propellant margin.
The two-orbit profile will also make use of the new capabilities of the Soyuz/Progress MS series, specifically its ability of orbit determination through satellite navigation and/or post-insertion ranging from the ground in order to target the orbit-raising maneuvers per the actual injection orbit and directly maneuver to the point where the Automated Rendezvous Sequence can be initiated.
留言
張貼留言