Started: June 21, 1997 -- Last Update: July 1, 1997
Viktor Kudielka (ÖVSV P3D Mission Analysis Project)
This document is intended as a base for discussion of alternative launch sequences of P3D. This part III considers the new launch schedules as well as changes of S/C and propellant masses.
P3D Launch Sequence Study, Part I, Dec. 5, 1996,
P3D Launch Sequence Study, Part II, Feb. 12, 1997
This scenario serves as a demonstration only, since impulsive mamoeuvers are assumed exclusively. The ideal target argP=315° is reached after about 1 year. The inclination of 61° at RAAN=230° makes shure, that an ArgP= 315° +/- 15° is maintained for about 11 years. The apogee will stay much longer (> 25 years) over the northern hemisphere. The height of perigee will increase to 8000 km. Other start times or dates will cause a substantial different behaviour.
The following table presents details of the powered flight phase.
Figures S1.1A and S1.1B show the whole period of powered flight. Figures S1.2A and S1.2B show the final drift phase.
This scenario is an attempt to find a proper balance of bi-prop and arc-jet operation. In addition the required deltaV is kept low, by compromising on the trend of ArgP during the final drift phase and also on the time needed for the orbital manoeuvers. Arc-jet operation is assumed to be in one hour intervals around perigee. The reduced efficiency due to the misalignment of flight path and spin axis is not yet taken into account.
Figures T1.1A and T1.1B show the whole period of powered flight. Figures T1.2A and T1.2B show the final drift phase.
The major drawback of scenario T1 is the very long time for the initial orbital manoeuvers. When we insist on the major inclination change at the first occurence of ArgP = 270°, we have to use the bi-prop motor for increasing the orbital period. In order to minimize the necessary bi-prop mass, we drop the initial inclination increase (for adjusting the argP) alltogether and start with an apogee very near the equator. We have to increase the orbital period as much as possible (assuming 89000 km height of apogee is the maximum for reliable operation) in order to use the arc-jet after the major inclination change for reducing the period to 16 hours. Most probably we could terminate the spin mode already after 130 days.
The final drift period does not look very attractive, but since some propellant for the arc-jet might be left, we can investigate a further orbital refinement later.
Figures T2.1A and T2.1B show the whole period of powered flight. Figures T2.2A and T2.2B show the final drift phase.
While T2 represents the attempt to reduce the elapsed time drastically, T3 demonstrates that a further reduction of the bi-pro deltaV requirements is possible. Arc-jet operations are assumed to last for one hour around perigee. ArgP is for a pretty long period near the equator, this is the price for the minimum bi-prop deltaV. Height of perigee is also low after the major inclination change. For an actual case some more refinements are necessary.
Figures T3.1A and T3.1B show the whole period of powered flight. Figures T3.2A and T3.2B show the final drift phase.
Scenario T4 uses the same strategy as T3 to go to a 32 hour orbit within the 90 degree drift of ArgP. Additionally there is a small (3 degrees) inclination change at ArgP = 180°, in order to get the apogee a little further north after the major inclination change. The size of this initial inclination change is restricted by the available mass of bi-propellant.
Figures T4.1A and T4.1B show the whole period of powered flight. Figures T4.2A and T4.2B show the final drift phase.