The rocket was carrying nuclear weapons, (allegedly) to be used against the Soviets.
Launch and coast to The Moon:
Sea Dragon 17 was launched 30 Miles of the coast of Guam successfully and entered orbit alongside Pathfinder which would protect it, as the Soviets are blockading the Moon to keep Sea dragon from reaching it.
Sea Dragon initiated Lunar transfer with Pathfinder beside it.
Sea Dragon and Pathfinder arrived in Lunar orbit where they were intercepted by the Soviet "Buran" shuttle.
As Buran approached Sea Dragon the crew of pathfinder consisting of Edward Baldwin, Sally Ride and G. Piscotty prepared to fire missiles at it, out of contact with Pathfinder mission control cannot tell Pathfinder to stand down.
However just before Pathfinder was supposed fires the missile, Ride refuses to participate and ends up holding Ed at gunpoint.
But Ride is unable to shoot Ed and instead she tries to reason with him to what seems like no avail as he fires the missile at Buran.
Suddenly Ed changes the missiles course away from Buran and destroys Sea Dragon 17, this ends the stand off as debris rain down on the Moon.