MIT engineers are developing a brand new spacecraft propulsion system that mixes the strengths of traditional chemical rockets with the efficiency and precision of electrical thrusters.
The technology could give small satellites far greater flexibility in space. As an alternative of counting on separate fuel systems for various kinds of maneuvers, future spacecraft could use a single propellant to perform each rapid movements and slow, highly controlled adjustments.
At the middle of the approach is a specialized fuel that works with each chemical and electric propulsion systems. Until now, these technologies have typically required separate propellants and hardware, adding weight and complexity.
“Should you can have chemical and electrical propulsion in a single small package, it’s the perfect of each worlds,” says Amelia Bruno, a former postdoc in MIT’s Department of Aeronautics and Astronautics (AeroAstro). “This opens the door for small satellites to do much more science, more observations, and more interesting missions, all on a smaller and cheaper platform.”
Bruno is the lead creator of a brand new study published within the Journal of Propulsion and Power. The research demonstrates that a “green monopropellant” originally developed by the U.S. Air Force for chemical propulsion may also successfully power miniature electric thrusters generally known as electrospray thrusters.
Combining Chemical and Electric Space Propulsion
Electrospray thrusters are tiny rocket engines, roughly the scale of a dime. They use electric fields to charge particles in a liquid propellant after which eject those particles into space, creating thrust.
These thrusters are extremely fuel-efficient and are well suited to gradual, precise maneuvers. For instance, they’ll slowly push a spacecraft through long interplanetary journeys while consuming little or no fuel.
Chemical thrusters serve a special purpose. They deliver powerful bursts of thrust that allow spacecraft to quickly speed up, decelerate, climb, descend, or change position.
By identifying a propellant able to powering each systems, MIT researchers imagine they’ll significantly expand the capabilities of small satellites.
The team is currently working with NASA on the Green Propulsion Dual Mode mission, a briefcase-sized CubeSat equipped with one chemical thruster and 4 electrospray thrusters. All of them will draw fuel from a single tank. The mission can be the primary try and test this kind of dual-mode propulsion system on a small spacecraft.
If successful, the technology could help small satellites enterprise far beyond Earth orbit.
“We could send CubeSats to Mars, or the asteroid belt, where they may make the journey slowly, using electrospray thrusters,” says study co-author Paulo Lozano, the Miguel Alemán Velasco Professor of Aeronautics and Astronautics at MIT. “You possibly can then use your chemical thrusters to quickly move to have a look at interesting features. You possibly can have rather a lot more flexibility to do rather a lot more things.”
Why Ionic Liquid Propellants Matter
Lozano’s laboratory develops, manufactures, and tests electrospray propulsion systems for satellites ranging in size from a lunchbox to a small carry-on suitcase.
Compared with larger spacecraft, these compact satellites are much cheaper to launch. Their smaller size, nonetheless, requires equally compact propulsion systems.
Electrospray thrusters fit that requirement well. The devices created in Lozano’s lab are concerning the size of a thumbnail. Each thruster sits above a reservoir containing an ionic liquid propellant. When connected to a battery, an electrical charge is applied to ions inside the liquid. Those charged particles are then expelled through tiny openings within the thruster, producing thrust.
Over the past decade, Lozano’s group has tested quite a few designs under different operating conditions and with quite a lot of ionic liquid fuels.
“Ionic liquids are very stable and might even remain a liquid in space, which not a number of materials can do,” Bruno says. “And it’s principally a sea of ions, which is why we base our technology around it, so we are able to pull those ions out into an electrospray.”
MIT researchers have also collaborated with the U.S. Air Force, which developed a brand new ionic liquid fuel generally known as the Advanced SpaceCraft Energetic Non-Toxic propellant (ASCENT). The propellant was originally designed for chemical propulsion systems.
ASCENT was created as a safer alternative to hydrazine, the highly toxic fuel traditionally utilized in many spacecraft propulsion systems.
“ASCENT happens to be an ionic liquid mixture,” Bruno says. “And we said, hey, that is the stuff we typically use. Theoretically, this could work. Let’s go determine how.”
Testing ASCENT in Electrospray Thrusters
To judge the fuel, Bruno, Lozano, and former MIT graduate student Matthew Corrado conducted a series of experiments using electrospray thrusters powered by ASCENT.
Each thruster was attached to a small cube-shaped reservoir roughly the scale of a LEGO brick. Researchers filled each reservoir with one gram of ASCENT, a liquid with a viscosity just like baby oil.
The thrusters were mounted on opposite sides of a CubeSat positioned on a custom magnetic levitation test platform generally known as the MagLev. The setup is positioned inside a big vacuum chamber that may recreate conditions just like those present in space.
During testing, the researchers remotely varied the voltage supplied to the thrusters. The resulting electrospray generated enough force to spin the CubeSat like a floating top.
By measuring the generated thrust and operating the thrusters repeatedly for periods of as much as 100 hours, the team was in a position to assess the fuel’s performance and efficiency.
The outcomes showed that ASCENT successfully powered the electrospray thrusters. The fuel performed on par with conventional ionic liquid propellants typically utilized in electric propulsion systems.
“In comparison with our normal electrospray propellants, ASCENT can provide similar performance when it comes to thrust,” Bruno says. “Now that we all know our thrusters work with ASCENT, we are able to start pondering of all of the ways we are able to make them even higher.”
NASA Mission Will Test Shared Fuel Tank in Space
With ASCENT now proven able to supporting each chemical and electric propulsion, researchers envision future spacecraft carrying a single fuel tank to power each systems.
That idea will soon face its first real-world test through NASA’s Green Propulsion Dual Mode mission, which is scheduled for launch in November.
“This can be the primary time that a satellite may have a shared propellant tank,” says Lozano.
Beyond deep-space exploration, the technology could also improve missions closer to Earth. Lozano points to weather and climate monitoring as one potential application.
“Say there is a storm coming, and also you’d wish to deploy your constellation of small satellites to watch over one location,” he says. “You possibly can decide to send them quickly or slowly depending on the character of the remark. And the one method to try this is that if you’ve got two propulsion systems, which is now possible.”
This research was supported partially by NASA.