NASA Space Technology
“A accurate put success memoir,” is how Experiments Manager William Kerslake described NASA’s 2nd Spot Electric Rocket Test (SERT II), the vital long-length operation of ion thrusters in put. SERT II supplied researchers with information for years past its expected lifetime and used to be a uncommon example of an entire mission – including the originate, propulsion scheme, spacecraft, and succor watch over center – being dealt with by one organization: NASA’s Lewis Analysis Center in Cleveland (these days, NASA Glenn).
The theorem that of electric propulsion thrusters dates support to the early Twentieth century, but on story of they must characteristic in a vacuum, there used to be no handy application for these systems unless the put program a protracted time later. In the leisurely Fifties, researchers at NASA Lewis began investigating sorts of electrical propulsion and analyzing missions that can possibly utilize these systems. They invent low quantities of thrust by constructing and accelerating dinky particles at high velocities, and over time, can scuttle spacecraft at very high charges of scuttle. Their skill to characteristic continuously for years at a time with tiny propellant makes them ideally suited for long-length missions or conserving satellites in orbit.
This work used to be expanded within the early 1960s with the introduction of Lewis’ Electromagnetic Propulsion Division and the building of tidy vacuum facilities, including the Electric Propulsion and Energy Laboratory (EPPL). Lewis engineer Harold Kaufman’s electron bombardment ion engine, which oldschool liquid mercury as its propellant, used to be the most promising option. Whereas Kaufman’s thruster used to be undergoing wide testing within the EPPL tanks, Lewis engineers began constructing a spacecraft to check the thruster. One day of the 50-minute suborbital SERT I flight on July 20, 1964, the Kaufman thruster grew to was the vital ion engine to characteristic in put.
Lewis continued improving the thruster scheme, and in August 1966 bought approval for SERT II. Researchers wanted to verify the thrusters might characteristic for longer intervals in put, opt their end on diversified spacecraft systems, and measure the degradation of voice voltaic arrays over time.
The center began simultaneous fashion of the SERT II ion thruster scheme and the spacecraft that can possibly plot it into orbit: a Thorad-Agena rocket. SERT II had two 15-centimeter diameter electron bombardment thrusters affixed to the support stop and a 5-by-40 foot voice voltaic array, the largest ever flown by NASA at that time, on the diversified stop.
After a series of tests within the EPPL, SERT II blasted off on February 3, 1970. Mission Manager Raymond Rulis called the originate “one in every of the smoothest operations I’ve considered.” SERT II used to be positioned into a round polar orbit that supplied its voice voltaic arrays with the precise daylight hours required to vitality its thrusters and electronic systems.
On February 14, 1970, Lewis engineers activated the vital thruster, starting its six-month operational check. Three weeks later, operators shut the thruster down unbiased correct earlier than the auto passed via the crawl of a voice voltaic eclipse. It used to be restarted with out explain afterwards and continued operation as the spacecraft encountered the eclipse a 2nd time later that day.
The thruster operated efficiently for five months unless an electrical short within the grid introduced about it to fail on July 22, 1970. Two days later, the 2nd thruster used to be activated. It operated smoothly for three-and-a-half of months unless a the same short came about in mid-October. Even supposing the SERT II thrusters didn’t fulfill their six-month wishes, they did characteristic for extended periods, confirming information obtained in Lewis’ vacuum tanks.
The mission continued when Lewis engineers reactivated SERT II in 1973 to demonstrate cathode restarting, and the following one year, they resolved an electrical short in one in every of the thrusters. One day of periods of intermittent daylight hours, operators demonstrated restarting the thruster with lower than an hour of vitality available. SERT II’s return to an orbit in precise daylight hours in 1979 supplied Lewis researchers the opportunity to behavior over 500 restarts. They operated the thruster for 18,000 hours earlier than the propellant ran out within the spring of 1981.
Over eleven years, SERT II supplied information on an entire bunch of thruster restarts, restarts after shutdowns as long as 18 months, ion beam neutralization of 1 thruster by the diversified, and discovery of a brand modern plasma thrust mode. SERT II additionally verified that thruster operation had no contaminated affect on spacecraft and voice voltaic arrays.
Silent, SERT II continued to be an asset to NASA researchers. In the leisurely Eighties, Lewis engineers realized that an auxiliary experiment on SERT II that analyzed the end of micrometeoroids on voice voltaic mirrors is also helpful to study on voice voltaic dynamic systems to vitality put stations. One day of six months in daylight hours in 1990, the Lewis team particular that after twenty years in orbit, there used to be no degradation of the voice voltaic contemplate’s optical properties.
Many technological parts of the SERT II thruster scheme enjoy been integrated into subsequent generations of ion thrusters. By the point the mission used to be terminated, Lewis used to be already ground testing thrusters twice the scale of these on SERT II. The center has continued to manual NASA’s electric propulsion efforts, constructing an array of technologies, including the NEXT-C thrusters that powered the Deep Spot 1 and Damage of day spacecraft. In beef up of the agency’s Artemis missions, NASA Glenn now not too long within the past examined the thrusters that can vitality GatewayNASA’s future lunar put station.
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