In-space propulsion system is “like the diesel engine on Earth.”
Mark Carreau
Following an 88-hr. 80-kW run, the Vasimr is ready for its next test. Credit: Ad Astra
Ad Astra Rocket Co. reached another milestone in its long-running quest to develop an electric propulsion capability to hasten the human exploration of Mars, tug cargos across cislunar space, round up the most worrisome orbital debris, deflect asteroid-impact threats as well as reboost, refuel and service satellites and future commercial space stations in low Earth orbit.
Ad Astra’s Variable Specific Impulse Magnetoplasma Rocket (Vasimr), housed within the 16-year-old company’s lab near NASA’s Johnson Space Center, wrapped up an 88-hr. run at 80 kW on July 12, a hard-earned benchmark.
Electric rockets, whether solar- or nuclear-powered, providing 50 kW of continuous electricity to convert the fuel surging through their thrusters to plasma are considered high power.
Conceivably, a Vasimr spacecraft equipped with a multimegawatt space nuclear reactor could journey to Mars with astronauts in 96 days, the first six of which would be spent spiraling out from the lunar-orbiting, human-tended stations such as the Gateway that NASA plans to begin assembling in late 2024.
Once at Mars, a descent vehicle could depart the mother ship to lower astronauts to the surface of the red planet for a 36-day stay on the surface. The Vasimr mother ship would glide by to retrieve the explorers and accelerate back to the Gateway over a 96-day return leg.
A similar undertaking using conventional chemical rocket propulsion would require 2-3 years, rather than the 7.5 months estimated for the Vasimr alternative. “We believe we have demonstrated that the Vasimr engine is a very competitive, high-power electric rocket for all the applications that might come with it,” Ad Astra founder, Chairman and CEO Franklin Chang Diaz tells Aviation Week. “We are now very satisfied.”
Chang Diaz, a former seven-time space shuttle astronaut, met with Aviation Week at the Ad Astra lab housing the vacuum test chamber. The stainless steel chamber features a radio-frequency heat source and superconducting magnets needed to first heat an argon fuel to extremely high temperatures, while surrounding the plasma and channeling the thrust.
“I want to demonstrate that the Vasimr engine is essentially the workhorse engine for heavy-duty transportation after launch and in space. It’s like the diesel engine on Earth,” says Chang Diaz.
The Costa Rican native is looking at May 20, 2035, as the date to start the notional 7.5-month trip to Mars, a mission facing a range of technical challenges that NASA hopes to address by establishing a sustainable human presence on the Moon in the 2020s.
Chang-Diaz traces his passion for electric propulsion back to his days at the Charles Stark Draper Laboratory, following his 1977 graduation from the Massachusetts Institute of Technology with a doctorate in applied plasma physics and fusion technology.
In 2015, Ad Astra was one of three companies NASA contracted with under the agency’s Next Space Technologies for Exploration Partnerships initiative to work on advanced electric propulsion with a goal of achieving a 100-kW/100-hr. demonstration. Under the initial three-year agreement, Ad Astra received $9.1 million.
While not achieving the 100-kW/-100-hr. goal, the company asked for a no-cost extension that formally expired on June 30. “We never had more than the $9.1 million, whatever it cost us,” says Chang Diaz. “We easily pumped in another $10 million.”
The challenge has been more than financial. Ad Astra announced on July 9 that it had achieved a 28-hr. run at a steady 82.5 kW on June 30, incrementally building up to the soon-to-be-surpassed milestone over the first half of the year.
The effort was halted at that point to give the company’s small staff a July 4 holiday break and an opportunity to assess the hardware. With a possible 100-hr./80-kW attempt still in mind, the staff returned from a stormy break only to discover a roof leak had allowed water to seep into a power element, shorting out a chiller. Damage to the roof and power element were repaired in order to accomplish the latest 88-hr./80-kW milestone.
A 100-hr./100-kW sprint is off the table, at least until Ad Astra can upgrade the Vasimr’s second-stage cooling unit to deal with power levels above 80 kW. “Eighty kilowatts is a lot of power. We wanted to exercise what we call an endurance test at 80 kW because we figured if we are going to replace that unit we will have to do surgery on the rocket, take it apart. There was a lot of learning we could do by initiating the test at 80 kW, so we decided to do that,” says Chang Diaz.
He credits much of the company’s recent advances to a 2018 agreement between Ad Astra and Aethera Technologies of Halifax, Nova Scotia, which provided a next-generation radio-frequency power processing unit with a full power rating of 120 kW. “Their hardware is the one driving the second stage,” says Chang Diaz, noting that all the Vasimr components were united in a vacuum for the latest milestone. “So we feel we are well positioned to be a very compelling technology for in-space transportation.”
The former astronaut believes strongly that NASA must come together with other elements of the federal government, and in particular the Energy Department, to back a solar power demonstration of the Vasimr technology in low Earth orbit, followed by a test of a nuclear reactor power source for deep space missions.
Like the oft-quoted SpaceX and Blue Origin founders Elon Musk and Jeff Bezos, Chang Diaz believes humanity must prepare to live and work beyond the Earth. “I don’t think we are all going to fit here,” he says. “The situation here is getting worse by the minute. We have pandemics. We have contamination. We have problems with food and air. Climate change is creating a lot of problems for a lot of people, which makes them migrate. It squeezes the space available.”
Last December, then-President Donald Trump issued his administration’s sixth space policy directive, which promoted the development of space nuclear power and propulsion by NASA in coordination with the Energy Department and Pentagon in order to facilitate establishing a sustained human presence on the Moon as well as journeying to Mars.
In July, the U.S. House Appropriations Committee approved a $25 billion NASA budget measure for fiscal 2022 that includes a $40 million investment in solar electric propulsion. The figure is $8.7 million less than the 2021 appropriation but $15.8 million more than the Biden administration’s request. The House measure also seeks $110 million for nuclear thermal propulsion development, equaling the 2021 budget, but $110 million more than requested by the White House for 2022.
Chang Diaz contends that with analysis, a solar-to-nuclear electric propulsion transition for human deep space exploration offers greater efficiency as well as lower mass, volume and cost advantages than a nuclear thermal propulsion alternative.
For Mars, NASA would be looking at a 5-10-megawatt reactor to power an argon-fueled Vasimr rocket engine. Once demonstrated in low Earth orbit with solar power, the Vasimr prototype and its nuclear reactor could make their way to a laboratory on the surface of the Moon with a staff prepared to move the test hardware from a pressurized laboratory out and back through an airlock for testing in the lunar vacuum.
“My thinking is we have something here that no one else in the world has,” says Chang Diaz. “It’s time for NASA to . . . at least give us a chance to demonstrate the value of our test for NASA and the nation.”
