The Apollo 13 mission may have been a near-disaster, but that didn't stop engineers from having some fun at NASA's (literal) expense.
The Apollo 13 mission remains one of the most memorable in NASA's history. Originally intended as the third lunar landing, the mission dramatically changed gears when an oxygen tank exploded, causing power fluctuations and prompting the crew to jury-rig systems to return to Earth safely. The fact that all three astronauts managed to survive was a testament to their skill and training, and even inspired the Ron Howard film starring Tom Hanks. It also inspired the Grumman Aerospace Corporation to have some fun at NASA's literal expense - posting a $312,421.24 bill to North American Rockwell for towing services.
When the Apollo 13 oxygen tank exploded, the spacecraft was 205,000 miles from Earth and roughly three-quarters of the way to the moon. The only way for the craft to return home safely was to swing around the moon, using the gravity as a slingshot that would send the crew back to Earth. The problem was the Command Module didn't have the resources to make the journey - after the oxygen explosion, all systems needed to be shut down to prevent further damage. That meant the astronauts had to run the mission using the Lunar Module's engine.
Thanks to the quick thinking of NASA and the Apollo 13 crew, the Lunar Module brought the craft back to Earth while jettisoning extra modules as it descended. But it's a feat the Grumman's engineers, who built the Lunar Module, didn't think would work - especially since the engine had to be fired multiple times for course corrections. That's why after the astronauts arrived safely, Grumman consultant pilot Sam Greenberg sent a tongue-in-cheek "towing invoice" to North America Rockwell.
Rockwell's response? According to the original report:
North American Rockwell, on receiving the invoice, had its Houston auditor examine it. Then the public relations director of its Downey, Calif. space division, Earl Blount, with a poker face issued a statement. He said that Grumman, before sending such an invoice, should remember that North American Rockwell had not received payment for ferrying [Lunar Modules] on previous trips to the moon.
Never let it be said astronauts can't have a sense of humor. To better understand what this historic event looked like at the time, here are a selection of photos from NASA's Apollo 13 Image Library.