The Paravulcoon was one of a multitude of proposed systems to permit recovery of Saturn boosters for reuse, and among the more delightfully eccentric. The scheme seems simple enough - the envelope emerges as a drogue chute, is rammed full of air, and then propane burners heat the air. After this, a controlled descent occurs. If you're especially bold, one can even use helicopters to tow the balloon to a favorable landing zone.
Scale testing of the system was done by the firm Raven, and proposals for use with the Saturn 1 and Saturn V were floated, but in the end nothing came of the project.
The Paravulcoon - a proposed recovery system for the Saturn rocket, using a hot air balloon to safely land the first stage after use
Watchung t1_jbpi2sf wrote
Reply to comment by Astronics24 in War in space: U.S. officials debating rules for a conflict in orbit by Azurebluenomad
And it doesn't bring up anything of substance about it, just a vague quote.