alternatehistory.com

March 15 1979

Kindley Naval Air Station, Bermuda

The space station was dying. And Naval Air Station Kindley was the only tracking station that could still transmit the UHF signals that operated the obsolete telemetry equipment aboard Skylab. With one control moment gyro inoperative and another ailing, with two coolant loops behaving erratically and several of the power-supply modules approaching the end of their expected life spans, the $2.5-billion orbiting laboratory was junk.

Very ironically – the space station carried a solar telescope - it was the incoming solar maximum that threatened to bring Skylab down erratically. After the fall of the Russian nuke sat Kosmos 954 over Canada early in the year, this was no longer acceptable.

Under ground control, an Agena closed from Skylab. It bore a lots of different names and accronyms: once know as the Teleoperator Retrieval System, it had been renamed the DART - for Demonstration of Autonomous Rendezvous Technology. The Astronauts for their part called it the Orbital Express.

After a launch by a Blue Streak the Agena hauled itself into its final orbit. Following its insertion in orbit the Agena started a series of manoeuvres, first climbing to its target level. From this point onward the slim rocket stage had been controlled from the ground. The time has come for the space tug to live its life and lock onto its target; before that, and just like a fighter chasing a bomber across the sky, it moved into an intercept manoeuvre, entering range of the LIDAR rendezvous system.

Far away, Skylab started emitting a homing signal across the emptiness of space. Long years before, the last men onboard had planted a beacon onto the old workshop. It was this homing system that the Agena antennas frantically sought. The two spacecraft were really playing hide and seek, and to this moment had not yet locked onto each other.

The Agena electronic brain did not panicked.

An impulse was send to the thrusters, and the stage pointed its signal to a slightly different elevation, with success. The LIDAR found the target voice, and locked onto it like an infrared missile on a hot turbojet. The two machines then started talking to each other; it was really an electronic chat between space vehicles.

Now the LIDAR had to know where Skylab was exactly.

The guidance system proceeded by a series of steps. First, the Agena pivoted to an angle so that it faced the target, not its side or its ass. The hemispheric correction achieved, a large antenna sprouted, scanning the sky to locate the target with more precision - range and range-rate cascaded across space, to the brain microchips. In response the Agena rapidly slid close to its target, and literally flew around it, gathering more information in the process before going the final moves of this eerie space ballet - final approach and docking !

Only 200m away did the Agena stopped again; final decision belonged to the ground. And it was positive, so the Agena moved again toward its target at a snail pace, the two space vehicles still chatting in their electronic gobbledygook.

As it closed from Skylab the Agena extended its 50 feet long robotic arm. Four years earlier, in February 1974 the departing Skylab 4 crew had bolted a grapple fixture near the front docking port. The Agena was to catch the grapple with its arm, and then flex the arm inwards to dock itself with the old space station. The maneuver was complex but it was a complete success.

Now the seven ton, diminutive Agena would face the daunting task of bringing the much heavier workshop down into Earth atmosphere.

It was really David against Goliath.

The Agena fired its small control thrusters many times – not even its main Bell engine, which brute force might have broken the workshop. That brought the orbit down to a hundred of miles. The Agena renewed its fight against the dead Skylab again and again, lowering the orbit further. The Agena was helped by the atmosphere; both plotted to diminish the workshop speed below orbital velocity. The result would be an immediate return to Earth. Loss of speed was minimal, 50 meter per second, but Skylab was already doomed.

And the Agena, its mission accomplished, would burn with it. Their graveyard would be a wet place: NASA controllers had picked an area 2,000 miles south-east of Fiji, far from any shipping lanes. The Agena last burn ended at 3:45 a.m. EDT; the workshop and its executioner went into an end-over-end spin, a fiery and deadly waltz.

Skylab had one more trick up its sleeve, however -one that gave flight controllers some anxious moments on the last orbit. They expected the cluster to come apart before it passed over the Atlantic ocean., but radar operators in Madrid reported only a single image. Over Indian Ocean the workshop still had not broken up; a NORAD imaging radar clearly showed that even the fragile solar arrays were still intact. But the telemetry was faltering and stopped entirely as the craft passed south of Australia. It finally fell in the South Pacific, only 1500 km from the cost of Peru.