Description from original post (created 2015-10-19 06:06):
"Sub-Orbital Suit designed for off-earth missions. Armor features integrated removable Booster Pack, specialized Maneuvering Thrusters, and heavy gauge Heat Shield."―(Iron Man 3 - JARVIS: A Second Screen Experience) The Mark 39's description in the JARVIS Application.
The Mark 39 (Mark XXXIX), also known by its names as "Gemini" and"Starboost", is a Sub-Orbital Suit, and was one of several new Iron Man Armors created by Tony Stark as part of the Iron Legion. The armor was created sometime after the Battle of New York.
It was featured in Iron Man 3, and made it's debut when Tony orderedJ.A.R.V.I.S. to initiate the "House Party Protocol" in which it was activated along with all the other suits to aid him in his fight against Aldrich Killian.
The suit earned it's name the "Starboost", for having the ability to travel intosub-orbital ranges and for venturing into space, as it is derived from it's name. It was built with an armor that could stand the cold temperature and radiation in space and was built in with an oxygen tank to allow Tony to be able to breathe while he was in space.
Tony's motive for creating this suit can be seen at the end of The Avengers. As Tony goes through the portal with the atomic bomb that would destroy Manhattan, his suit powers off. Stark then falls through the portal and is saved by the Hulk.
this text by...
Mark 39 - Iron Man Wiki - Wikia