From the dawn of the space age, space objects have traveled along predictable, gravity-driven paths first defined by the German Renaissance astronomer and mathematician, Johannes Kepler.
For decades, those predictable orbits served our nation well; space was essentially a sanctuary. But in our now-congested, contested, and competitive Space Area of Operations (AOR), Keplerian orbits will no longer cut it.
At public appearances, including at the 2023 Space Symposium in Colorado Springs, Colo., then Deputy Commander of U.S. Space Command (now retired) U.S. Space Force Lt. Gen. John Shaw, said maneuverability – regardless of domain – enables military forces to move quickly, sidestep defenses and achieve surprise. Space, he said, should be viewed no differently than any other operational domain.
“Dynamic Space Operations, or DSO, at its heart is about being able to maneuver once on orbit,” said Tom Wehr, director of business development for launch and space exploration at Aerojet Rocketdyne, an L3Harris Technologies company. “Maneuverability complicates an adversary’s planning and targeting.”
For example, because ground-surveillance satellites follow predictable orbital paths, adversaries typically know when one will be overhead and can modify their behavior accordingly, Wehr said. Similarly, space surveillance operations would benefit from the ability for satellites to maneuver to take a closer look at objects of interest. And if conflict breaks out in the space AOR, maneuverable satellites can complicate an adversary’s ability to target and deny our space superiority.
“All of that requires more propulsion capability than what you’ve typically seen in the past,” Wehr said.
Aerojet Rocketdyne, a longtime global leader in rocket and in-space propulsion, offers several DSO-enabling capabilities, with more in development. These propulsion capabilities provide the speed and efficiency to maneuver without regret. Some examples include:
- Electric satellite thrusters with 10 times the efficiency of conventional chemical propulsion systems.
- A long-life version of the company’s high-thrust RL10 upper stage rocket engine, capable of multiple of in-space restarts, an industry workhorse that has sent probes across the Solar System and beyond.
- High-performance propellants that are more efficient and environmentally friendly than hydrazine and other chemical fuels typically used for in-space propulsion.
- Air-breathing electric propulsion systems for satellites operating in very low Earth orbit, or VLEO. Because they draw their propellant from the residual atmosphere in VLEO, these systems have virtually unconstrained maneuverability.
- Long-life mono-propellant thrusters for refuelable space vehicles.
- High Delta-V Integrated ESPA (EELV Secondary Payload Adapter) Propulsion Systems to provide significant maneuverability capability to smaller space vehicles.
- Long-life, high-performance bipropellant liquid rocket engines for higher-impulse DSO maneuver requirements.
- On-orbit refueling and propellant management systems for monopropellants and cryogenic propellants.
“Aerojet Rocketdyne provides highly reliable and long-life propulsion solutions for any mission,” Wehr said, emphasizing that when it comes to DSO, there is no one-size-fits-all system.
Electric propulsion is one example; it is ideal for mass-constrained satellites that do not require high-speed or long-distance maneuverability. These systems enable planners to devote only a small amount of total available satellite mass to propellant, he said.
Aerojet Rocketdyne’s electric thrusters have long been operational aboard commercial and government satellites, and the company is developing higher power systems to support NASA’s exploration goals. Electric thrusters provide low-thrust, high-specific-impulse propulsion for missions needing more efficiency than speed.
Additionally, Aerojet Rocketdyne is working on a longer-life RL10 upper stage engine that could relocate payloads days or even weeks after launch, making them difficult to track, Wehr said. In one scenario, a primary satellite might initially be launched to geostationary-orbit (GEO), and the upper stage then maneuvers a secondary payload into a disposal orbit – an area of space above the GEO arc that serves as a graveyard of sorts for spent hardware. The upper stage could then restart on demand and deliver the secondary payload to the orbit required to perform its mission.
“The long-life RL10 complicates an adversary’s thinking because they now have to track everything in the disposal orbits because they might do something later on,” he said.
Restarting an RL10 that has been inactive for extended periods in the extreme cold of space is a “nontrivial” challenge, Wehr said.
Another DSO capability of interest to the Space Force is on-orbit satellite refueling, and this is another area where Aerojet Rocketdyne’s products shine. Aerojet Rocketdyne’s chemical and electric propulsion systems have an unrivaled operational track record that gives mission planners confidence in their durability and ability to safely conduct proximity operations.
“Refueling doesn’t do any good if your thrusters are going to burn out,” Wehr said. “You’ve got to have a thruster that you can keep using and that’s where we have an advantage.”
That translates into a Space Force advantage as it deals with increasingly capable adversaries in a contested space environment. DSO is about upending the predictability that has traditionally defined orbital operations through propulsive maneuverability, something that plays to the strengths of Aerojet Rocketdyne.
