NanoSail-D has always held a special place in my affections, probably because the solar sail effort has, until recently, been stalled. The IKAROS sail brought us into the sail age with gusto, but the sail team at NASA’s Marshall Space Flight Center has persisted through budget uncertainties and public indifference in finding a way to create a space-going sail seemingly out of thin air. No, it wouldn’t be the large, free-ranging sail we might have expected a few years back that could have so easily grown out of MSFC’s work, but it could be launched on the cheap. It could make it into space, and once there its short mission could break the trail for future sail efforts.
Remember that NASA developed two different 20 X 20-meter solar sails between 2001 and 2005, one fabricated by ATK Space Systems, the other by L’Garde Inc. Both these sails were tested in ground vacuum conditions, and MSFC’s Les Johnson pointed out in 2008 that they were solid designs, “… robust enough for deployment in a one atmosphere, one gravity environment and…scalable to much larger solar sails — perhaps as much as 150 meters on one side.” NanoSail-D, its sail made of a polymer called CP1 that is no thicker than single-ply tissue paper, finally gets NASA into actual space operations with an inexpensive demonstrator.
The First Test Passed
And so far, so good. While the first NanoSail-D perished in the launch attempt, the second has now been successfully ejected from the FASTSAT (Fast, Affordable, Science and Technology Satellite) that took it aloft, the latter equipped with six science and technology demonstration payloads when launched on November 19. The NanoSail-D ejection from FASTSAT is actually the first time NASA has ejected a small cubesat from an autonomous, free-flying microsatellite, and I’m delighted for the team and NanoSail-D principal investigator Dean Alhorn, who said this:
> “This is a great step for our solar sail team with the successful ejection of the NanoSail-D satellite from FASTSAT. We had to carefully plan and calculate the ejection time, so we’d be lined up over the United States and our ground controllers to execute the next phase of the mission.”
Or in the more direct language of Twitter, in the form of two tweets from the NanoSail-D team (continuing coverage @NanoSailD):
> Door is open. We have carrier!!!!!!!!!!!!!!!
> That means we have ejected. Whew!
A bit of a white-knuckle moment indeed, with a bigger one to follow. That next phase will include a three-day countdown that will culminate in the crucial sail deployment, with the unfolding of NanoSail-D’s 32 square-meter polymer sail. The entire process takes about five seconds and, if successful, leaves the sail in low-Earth orbit for a period ranging from 70 to 120 days, depending on atmospheric conditions. Deploying a compact solar sail boom system is a major challenge of the enterprise, but so is measuring the effect of solar photons in an orbit low enough that atmospheric drag effects can mask the push from the Sun. The low orbit is part of NanoSail-D’s other mission, to test systems that could be used to de-orbit future Earth satellites.
Gritty Persistence and the Sail
We’ll follow NanoSail-D’s deployment fortunes with great interest. Meanwhile, ponder this: After the ground testing on two independent sail concepts, solar sail work at NASA seemed stalled. When NanoSail-D did emerge, commissioned in 2008, its team was given a mere four months for design and testing. Solar sailing was back, though with tight constraints of time and budget, followed by launch failure aboard a SpaceX Falcon 1. It’s the NanoSail-D spare we’re now testing in space, a case of making do with whatever parts were available. As Dean Alhorn says:
> “It wasn’t a question of going off and doing an exhaustive study of what components to use. There was no time for that. We said, ‘Okay, this is the size of component we need, this is its function’ — and as soon as we found one that worked, we used it.”
NanoSail-D is what happens when people simply refuse to give up on a concept they believe in. Budgets get cut, people get assigned to new tasks, public interest drifts to other topics, but if you believe in what you’re doing, you continue to make the case. And if your mission isn’t as large or complex as you might have wanted, if it’s coupled with an auxiliary task (de-orbiting) that makes your measurements of solar sail effects that much harder to measure, then you find a way to make the best of it and get the sail deployed. That’s gritty, persistent engineering, and I’m hoping it pays off with a successful deployment and a green light for the next iteration of NASA sails.