5.4.1: Pioneer Days

This year marks four decades since the launch of the first artificial satellite PS-1 by the Soviet Union. The Soviets used liquid rocket engines for space applications almost exclusively until the 1990s, with the exception of deorbit engines, although the Korolev and Nadiradze bureaus did develop solid propellant ICBMs. In other countries, however, solid rocket motors have played a key role in delivering satellites to their final orbits for most of the years since Sputnik. America's first orbital launch attempt, Vanguard TV3 in Dec 1957, used a Grand Central Rocket 133-KS-2800 solid motor as its orbit insertion stage. Of course, the solid motor never fired on TV3 as the shot ended in an ignominious pad explosion, but the GCR stage did successfully enter orbit on two later missions with the Vanguard 1 and 2 satellites. Two months later, a successful Jupiter C shot placed Explorer 1 in orbit. The upper stages for Jupiter C were developed by the Jet Propulsion Laboratory; they scaled down their Sergeant missile motor to make the RTV (Reentry Test Vehicle) motor. The original RTV motor used a polysulfide fuel in a steel case; the Explorer 1 satellite was built around the final stage RTV motor. Explorer 4 introduced a higher performance polyurethane fuel and the Pioneer 3 lunar probe saw the use of a titanium motor case for the first time.

The first satellites used a stack of stages firing in sequence with relatively little coast time, with the final stage providing orbital insertion a few hundred kilometers downrange. Most of these early satellites were in elliptical orbits with relatively low perigees. In 1957, William Pickering and his team at the Jet Propulsion Laboratory realized that they could easily lengthen the orbital lifetime of their low-perigee Explorer satellites by including a small `Two Pound Rocket Motor' which would wait on a timer to fire until the satellite had made exactly half a circuit of the Earth. Now this was before we got clever about active satellite attitude control, and their plan was to mount the motor nozzle upside down, so that retaining its inertial attitude half an orbit around would leave the nozzle pointing back along the velocity vector, allowing the burn to raise perigee and prolong the orbital lifetime. Pickering gave this idea the colorful name of the 'Kick in the Apogee' technique. At around the same time the rival Navy team at China Lake (Naval Ordnance Test Station or NOTS) came up with the same idea and discussed it with Pickering; there is some question that the concept may go back as far as Peenemunde, but Pickering was definitely responsible for the name, which led to today's term of `apogee kick motor'.

The first launch attempt was made by the NOTS team in July 1958. Their small cylindrical satellites were launched by a four-stage vehicle from an F-4D Skyray. This was the first attempt to launch a satellite from an aircraft, similar to today's Pegasus system. The satellite, nicknamed `NOTSnik', was originally intended as a military weather satellite. It was modified as a diagnostic payload for the Project Argus high altitude nuclear tests. The `NOTS 3 in. Spherical Motor' would have provided the kick in the apogee. The aircraft took off from China Lake and headed out to the ocean for the drop; 53 minutes after launch the apogee motor would have fired to place the satellite in a 2400 km circular orbit. Despite some claims from NOTS team members, most analysts believe that all six launches in July and August of 1958 were failures well before the kick stage would have come into play. JPL's try was in connection with the Army's inflatable Beacon satellite in October of the same year, but once again the technique could not be tested, when the upper stages separated prematurely during first stage burn and inital orbit was not reached. [Sources: Jupiter Bimonthly Summary No. 12, JPL, 1958; Project Pilot Informal Research Package, NOTS.] After these two failures, the solid apogee motor remained in limbo for several years. Explorer 6 used a small perigee rocket to increase its apogee in Aug 1959; in April 1960 a technique similar to that of apogee motors was used for the first time, but using a restartable liquid rocket - the Transit 1B navigation satellite was placed in circular orbit when the Ablestar rocket reignited after a 20-minute coast phase. In early 1963, a series of small classified Lockheed satellites used a solid motor to enter a higher circular orbit after deployment from CORONA recon satellites: I don't have any details on this motor.

It was in Feb 1963 that the apogee technique got its first real test, when the Syncom 1 satellite carried a Thiokol solid apogee motor to geosynchronous altitude. Unfortunately, the motor seems to have exploded on ignition, and Syncom 1 was lost. It was not until July 1963 that the `kick in the apogee' concept was brought to fruition, when a JPL kick motor successfully placed Syncom 2 in a circular synchronous altitude orbit.