VASIMR: This plasma engine could get humans to Mars in only 45 days

Humans haven't even reached Mars yet, but one former NASA Space Shuttle astronaut is already working to drastically reduce travel times to the red planet.

Dr. Franklin R. Chang-Díaz (Ph.D.) retired from NASA in 2015 having logged 1,500 hours in space across various missions, including 19 hours of spacewalks at the International Space Station (ISS).

Now, the ex-NASA astronaut's focus is on Costa Rica and US-based firm the Ad Astra Rocket Company, which he founded in 2005 with the aim of reducing the amount of time it will take to send humans to Mars. It's a mission that could greatly improve crew safety for future human missions to Mars.

To make this ambitious goal a reality, the private space company is building a high-power electric propulsion engine called VASIMR that could one day power a nuclear electric rocket to Mars in as little as 45 days.

"For me, this is the one thing that needs to be done for humans to go to Mars," Chang-Díaz told Interesting Engineering (IE) in an interview earlier this month.

What is VASIMR the Mars-bound nuclear electric engine?

Ad Astra's Variable Specific Impulse Magnetoplasma Rocket (VASIMR) engine is an advanced high-power propulsion system that can heat plasma from anywhere between one to five million degrees.

In order to power the engine, a gas (such as Argon, Helium, or Hydrogen) is injected into VASIMR's so-called "rocket core", which is split into three stages.

The first stage uses a Radio Frequency (RF) coupler to heat the gas and produce plasma. The plasma then moves into the second stage, where it is energized by more Radio Frequency power from a second RF coupler. In the third and final stage, the plasma energy is converted to high exhaust velocity using electricity, and a magnetic nozzle then ejects the plasma out of the engine.

You can watch a detailed animation of the process in the video below.

This process provides thrust at speeds of up to 123,000 miles per hour (197,950 kilometers per hour), meaning the engine could power a rocket to Mars in roughly 45 days.

The VASIMR engine will require a space-worthy nuclear reactor to propel a spacecraft. For this technology, Ad Astra will rely on other companies to hopefully provide the required technological innovations over the coming years.

As a point of reference, NASA recently announced a partnership with DARPA to test a nuclear rocket in space by 2027. However, that rocket will use the nuclear thermal approach where heat from a nuclear fission reaction is used for thrust. Ad Astra will use the nuclear electric approach, where a nuclear reactor generates electricity to power its engine.

In his interview with IE, Chang-Díaz pointed out that Ad Astra will likely first run a solar-powered version of VASIMR for missions closer to home.

"We will probably deploy 150-kilowatt engine modules that will be broadly solar powered," he explained. "Logistics is becoming a really important element in making sure that the space economy thrives and evolves quickly. And that means you need heavy-duty transportation."

A space demonstration of VASIMR in the near future

Ad Astra faces a few hurdles before it can test its technology in space.

"The timeline for when we’ll see a VASIMR demonstration in space is all dependent on the funding," Chang-Díaz told IE. "Right now, to get this engine ready to fly, we're going to need something on the scale of $150 million (dollars). To launch it to space we'd need maybe another $50-60 million."

If that investment were secured now, "we could see this engine flying three years from now". Until that happens, however, "everything else will continue to inch along."

"The technology is there," Chang Díaz continued, "and what we're trying to do now is turn the package we have in a laboratory vacuum chamber into something that’s flight-worthy."

Back in 2021, Ad Astra completed a record 88-hour high-power endurance test of its VASIMR VX-200SS plasma rocket at 80 kW.

That marathon endurance test "demonstrated that the VASIMR engine is able to operate pretty much indefinitely at high power," Chang-Díaz said. "It moved the technology from technology readiness level (TRL) four to five, and to borderline level six," he explained. "Our goal now is to transition the technology into flight readiness."

If it succeeds, Ad Astra will massively reduce travel times to Mars for crewed missions, as NASA estimates it will take approximately seven months with existing technologies. This would greatly reduce the crew's exposure to space radiation and would dramatically reduce the probability of an anomaly causing a mission failure.

Ultimately, it would be a crucial step towards making humanity a truly spacefaring civilization.