Soft ride method for changing the altitude or position of a spacecraft in orbit

A method of transporting a payload on a spacecraft from an operational orbit to a low-altitude parking orbit around a planetary body, said method comprising the steps of:

• actuating a low-thrust liquid bipropellant rocket engine for at least one burn at a preselected point in the operational orbit, to decrease the velocity of the spacecraft at that point in the orbit and place the spacecraft in an eliptical orbit about the planetary body such that the preselected point is the apogee of the eliptical orbit;
• and
• actuating the rocket engine for a succession of burns occuring at the perigee in the eliptical orbit, and thereby decreasing the velocity of the spacecraft at perigee until the orbit is circular at perigee altitude;
• whereby the parking orbit is reached by a succession of relatively short burns producing relatively low levels of acceleration.

A method of transporting a payload on a spacecraft from a low-altitude circular parking orbit to a higher-altitude operational orbit, said method comprising the steps of:

• accelerating the spacecraft to a higher velocity at a preselected point in the parking orbit, thereby moving the spacecraft into an elliptical orbit having a perigee at the preselected point and an apogee higher than the original parking orbit;
• accelerating the spacecraft to a slightly higher velocity each time the perigee is reached, thereby extending the apogee to a higher and higher altitude;
• and then
• accelerating the spacecraft once more at a time when apogee is reached, to circularize the orbit at a desired altitude, whereby only relatively small accelerations may be used, and components of the payload may be deployed before departure from the parking orbit.

A soft ride method for changing the position of an orbiting satellite comprising the steps of:

• selecting an orbital location for commencing a soft ride change in orbital position;
• providing a relatively low acceleration thrust;
• altering the velocity of said satellite;
• and
• repeating said thrust until a desired orbital position is achieved.

A spacecraft for transporting a payload from a low-altitude parking orbit around a planetary body to a higher-altitude operational orbit, the spacecraft comprising:

• (a) means for attaching the payload to the spacecraft;
• (b) a low-thrust liquid bipropellant rocket engine;
• and
• (c) control means for (i) actuating the engine for a relatively short period at a preselected point in the parking orbit, and thereby increasing the velocity of the spacecraft at the preselected point in orbit, and for (ii) actuating the rocket engine for a succession of relatively short burns each time the preselected point in orbit is reached, the preselected point becoming the perigee of an elliptical orbit at which the apogee moves further from the earth after each successive orbit, the relatively short burns producing relatively low levels of acceleration.