A year and a half after it suddenly stopped working on its maiden voyage, Explorer, a state-of-the-art hybrid boat and floating classroom, is expected to arrive on the Ohio River in Pittsburgh today.

Since Aug. 3, the boat, built for the nonprofit science education organization RiverQuest, has been on a 1,600-mile journey through nine states, starting in Bayou La Batre, Ala. Explorer should dock next to the Carnegie Science Center by early afternoon, according to RiverQuest. Passengers will board after United States Coast Guard inspections are completed.

The $3.5 million vessel is one of the world's first green-engineered floating classrooms and will be used to teach about ecology, environmental science, energy, climate change and river history, among other topics.

It broke down in March 2007 after its gearbox broke 200 miles into the boat's 1,700-mile maiden voyage from a Florida shipyard.