Little Moon Capstone Mission – How a ‘shoebox’ should pave our way into space

Do you want a trip to the moon? That’s only four to five days – at least with a one-way ticket. But for NASA’s Capstone mission, the moon is three to four months away. The small space probe, which is only the size of a microwave oven, is intended to test a fuel-efficient pathway. In the future, larger unmanned missions to the Moon will follow the same path.

MDR WISSEN was able to win a NASA employee for an interview for the first time. We spoke to Elwood Agassid about Capstone – an acronym for Cislunar Autonomous GPS Technology Operations and Navigation Experience.

Agassid admits, “A lot of people ask about the name and I call it Capstone because the other name is tongue-tied. And it’s actually hard to remember, frankly.” He is deputy director of the Small Spacecraft Technology Program, which the agency plans to test in the environment of the Moon and Mars in the near future. As part of the Artemis lunar program, Capstone is one of them.

Capstone: A Guide to Human Spaceflight

For Agassid, the Capstone is a kind of beacon for the Lunar Gateway — a space station planned to orbit the Moon for up to 15 years in the middle of 2020. It’s meant to be a stopover for astronauts on their way to the lunar surface.

But there’s a catch: such a space station doesn’t just need water and oxygen for its crew. Above all, it needs fuel. This cannot be earned in space yet, but must be brought from Earth. The more fuel you carry, the heavier the payload. The heavier the payload, the more thrust the rocket needs to get out of orbit – ergo: more fuel is needed.

On the direct route to the Moon, which averages about 384,400 km, you use a lot of fuel. To stay in orbit around the Moon, the Gateway must perform corrective maneuvers. In order to continue to save fuel, NASA has chosen two special orbiters. Capstone should test them.

The Road to the Moon: Capstone and the Lunar Gate

On the way to the Moon, Capstone will carry out a ballistic transfer to the Moon. The space probe uses the gravity of the Earth, the Sun, and the Moon to be eventually detected by the satellite’s gravity. “It takes some time to get to the moon with this ballistic transfer to the moon. It doesn’t require a lot of fuel,” Agassid says.

Once the probe reaches its climax – the point farthest from Earth – it will use the moon’s gravity to enter its orbit at the point closest to the moon (perihelion). This will be the case after 1.5 million kilometers.

“Then the spacecraft will start a circular burn to get it to its final location” – in the NRHO (Near-Right Halo Orbit, also known as the Halo Orbit). Unlike the Apollo missions, the probe will not orbit the Moon along the equator but along the poles.

Entering Halo’s orbit

It’s important for a future Moon Gate because it “has a continuous view of Earth for communication purposes. It’s also a very stable orbit and doesn’t require much fuel to maintain the station,” Agassid says.

Capstone will orbit the moon’s north pole at a distance of about 1,600 kilometers every seven days. Antarctica is 70,000 km long. Capstone uses “sort of Lagrangian point and Earth-Moon gravity” to do this and, according to Agassid, will require only a few corrective maneuvers to stay in orbit.

independently through the galaxy

The space probe will not be able to perform many of these maneuvers. Fuel accounts for only 20 percent of their weight. With a weight of 25 kilograms, that means roughly five kilograms of fuel. Quite enough, because “the main goal at the moment is to determine the requirements for a flight to Halo’s orbit and find out how much fuel is needed.”

Another goal of the six-month mission is the spacecraft’s navigation and communications capabilities. Once on the moon, Capstone will establish a cross link with the Lunar Reconnaissance Orbiter (LRO). This has been on the moon since 2009 and it’s all set.

The cross connection allows the Capstone to determine its position independently. To do this, the probe uses a high-frequency signal that is sent back and forth between Capstone and LRO using onboard hardware and software. Capstone then measures the speed of the signal to determine the location.

What people aren’t clear about is that right now, all NASA missions are done in deep space – frankly, all deep space missions, whether it’s ESA or NASA or other international space agencies – are done from controlled Earth.


Elwood Agassid, Deputy Director of Programs at NASA

When does the Capstone mission start?

Capstone is scheduled to blast off into space from June 13 aboard the modified Electron small launch vehicle from private space company Rocket Lab. The missile can be launched any day until June 22 from Launch Complex 1 in the New Zealand port of Mahia Peninsula.

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