This week, the Cassini-Huygens Saturn probe, in operation for 20 years, was deliberately sent into an path to enter the gas giant’s atmosphere to be destroyed. A part of it, the Huygens probe, rests on the surface of Titan, possibly lapped by methane seas or snow.
Cassini was not the first nor the last NASA spacecraft to meet a planned destruction. The recently-arrived Juno probe will also meet a searing end in Jupiter’s atmosphere sometime by 2019.
Here are a few notable occasions of glorious destruction and the background.
Note: With one exception, we’re talking only here of NASA interplanetary spacecraft with successful launches and deployments that complete their missions prior to destruction. There have been hundreds of rockets and spacecraft which were intentionally deorbited from earth orbit at mission’s end (such as Orbital’s Cygnus cargo supply ships) or come back to earth because of serious flight abnormalities, bad orbits, bad engineering and plain bad luck. For brevity, we’re also not counting probes where communications are ceased when the mission ends for other non-destructive reasons, such as batteries dying.
The first flight test of the Gemini spacecraft with its Titan II booster launched on April 8, 1964. This unmanned mission was simply to verify the structural integrity of the booster and spacecraft and verify some spacecraft flight systems over three orbits.
Since this launch was at a time where the United States was still behind in the Space Race, what secrets could be kept by the Americans (given that NASA was a public agency) were still important. Before flight. engineers drilled several large holes in the vehicle’s heat shield, and Gemini 1 stayed attached to its second stage during the flight.
Gemini 1 was left to self-destruct as there were no plans for NASA to recover (or let the Soviets recover) any of the vehicle.
Magellan was a Venusian space probe, the first interplanetary spacecraft launched via Space Shuttle, on May 5, 1989.
Magellan was among a small but promising list of new interplanetary spacecraft originally meant to be launched by the Shuttle with a much more powerful escape-velocity space, a variation of the Centaur rocket stage used for years on Atlas and Titan III and IV launch vehicles. But after the 1986 loss of Space Shuttle Challenger, safety considerations cancelled the Shuttle-Centaur project, and Magellan would be the first to use a less powerful two-stage solid rocket called the Inertial Upper Stage. The Shuttle delays also causes the optimal window for Magellan to reach Venus in a shorter time.
The IUS could manage to push Magellan out of earth orbit but lacked the power to push Magellan directly to Venus. It took 15 months more, using the sun as a gravity assist, to swing the probe into Venusian orbit.
With the Venusian surface covered by thick acidic clouds, Magellan’s used radar to map nearly the complete surface of the planet over four glorious years. The probe found ample evidence of volcanic activity, slowed by the high pressure atmosphere, and a geologically young surface with few craters since the atmosphere’s density would easily destroy all but the largest meteors.
Magellan was also the first probe to test aerobraking, using a celestial body’s atmosphere to adjust a spacecraft’s orbit.
With the primary and secondary missions completed, with solar power systems starting to fail appreciably and with maneuvering fuel low, Magellan was directed to a special gas-density mission, skimming and eventually entering the Venusian atmosphere by October 13, 1994.
Galileo Jupiter Spacecraft
The Galileo spacecraft, like Magellan, was launched by an IUS from Space Shuttle Atlantis on October 18, 1989. With only the IUS, Galileo required multiple gravitational slingshots–one around Venus and two around Earth–to gain sufficient speed to reach Jovian influence five years later.
Despite the failure of its central communications array to fully deploy, Galileo was able to send incredible data and photos of the gas giant and its many moons large and small, as well as the incredible impacts of pieces of Comet Shoemaker-Levy 9 in 1994. Shortly after arrival, Galileo carried a smaller probe that was launched into the Jovian atmosphere, making studies of gases and pressures.
One very notable study in the probe’s extended mission was an detailed study of the icy moon Europa. Galileo’s findings, particularly that the moon may have an water ocean underneath its ice, has prompted NASA to begin work on a new Europa probe.
To avoid contamination of any of the Jovian moons and with fuel too low to make further studies, Galileo made a suicide dive towards Jupiter, ending itself on September 21, 2003.
The first probe to attain orbit around the planet Mercury, the closest planet to the sun, the MESSENGER (Mercury Surface, Space Environment, Geochemistry, and Ranging) spacecraft was launched on April 4, 2004 by way of a Delta II launch vehicle.
With limited launch power, MESSENGER used one flyby of Earth, two flybys of Venus and three flybys of Mercury itself to reach the tiny planet. Because of the proximity of the planet, making orbit around Mercury was far trickier than other probes because of gravitational weirdness so close to the sun.
During its lifetime, MESSENGER mapped the entire surface of Mercury and discovered that this tiny super-hot planet had a small but measurable magnetic field (unlike Venus and Mars). Also of interest was that the planet’s north pole had water ice resting below the surface.
Low fuel reserves compelled the mission commanders to tell MESSENGER to make a core sampling of Mercury’s surface at 8,750 mph (14,080 km) on April 30, 2015.