A Starfleet spacesuit fitted with a detachable thruster pack for independent flight, which Spock takes without permission to fly into the heart of V'Ger.
The thruster suit is an environmental suit of the 2270s combined with a large back-mounted rocket unit, allowing the wearer to cross long distances in open space without a shuttle. It appears in Star Trek: The Motion Picture.
As the refitted Enterprise is held inside V'Ger, Spock overpowers a crewman at an airlock, takes a suit and launches himself through the orifice leading to the vessel's inner chamber. He passes images of the worlds V'Ger has stored and attempts a mind meld with it, which overwhelms him.
Kirk follows in a second suit and catches the unconscious Spock as he drifts back. The experience shows Spock that V'Ger, for all its knowledge, is empty, and changes his view of his own pursuit of pure logic.