Massachusetts' growing robotics cluster just got bigger. For the second time in less than six months, an iRobot co-founder has launched a robotics startup. Helen Greiner told me in an e-mail yesterday that she has formed a stealth company called The Droid Works. "Our first project is in the UAV [unmanned aerial vehicle] space, and a team of people from around the country are working on this project today," her short note said.

Beyond that, the note contained little, and Greiner (our newest Xconomist) didn't say much more when I reached her on her cell phone, declining to discuss how the company was funded, the number of people involved, or anything else of substance. "I am not ready to describe the types of UAVs, missions, or what the company will take on in the future yet," her note said. The one thing she clarified on the phone was that she didn't mean to imply - as I had wondered about from her note - that The Droid Works is a virtual company. Rather, all she meant by saying people are working from around the country, she says, is that not everyone working on the first project is based in the Boston area.

A shell website can be found here. If I had to guess from its name, The Droid Works might be set up to tackle different types of projects in robotics, rather than being focused solely on UAVs. I also think the website looks like it has the same designer as fellow iRobot co-founder Rod Brooks's Heartland Robotics, so I can't help but wonder if there is a connection between Brooks's firm and Greiner's, or if they might be sharing space in Cambridge's Central Square, where Heartland is based.

Greiner's venture comes a little more than five months after Brooks (who's also an Xconomist) left iRobot, where he was CTO, to found Heartland, which is focused on creating workplace robots.

Greiner herself stepped down as chairman of iRobot's board and as a full-time employee about seven weeks later, in late October. Like Brooks, she remains on the iRobot board.

When I reached her the day her iRobot departure was announced, Greiner related how she had gotten hooked on robotics when she was 11, and that she had no intention of leaving the field. However, she said she was going to take some time to reflect and continue her public service work - she serves on the boards of MIT and the Boston Museum of Science, and as chair of the national Robotic Technology Consortium, among other roles - before making any decisions about her career. "I'm going to keep doing all of those things while I take a look around at what I want to do next," she told me.

I even asked her at the time if she was joining Brooks at Heartland or had her eye on some other company. "I honestly don't have any entity that I'm thinking about right now. I really want to be able to take a look around, and I would never feel comfortable doing that as chairman of iRobot," Greiner said.

Now it appears she has found her comfort zone.