WARFRAME on Twitter: "We're making it easier to build your Railjack by reducing costs! If you've already started or finished Rising Tide, you'll receive a gift of Rush Repair Drones and refunded
You can get rush drones from rare boxes on railjack bases. : r/Warframe
Railjack – WARFRAME Support
How do I use rush repair drones...? - Players helping Players - Warframe Forums
Warframe - Railjack Wreckage Guide | Attack of the Fanboy
Rush repair drone should be back on the market : r/Warframe
Rank 10 Engineering doesn't actually repair anything. It DOES spawn a repair drone each time you try to use it, however... : r/Warframe