Apollo 12 had detected frequent impacts of small objects onto the Moon, but larger impacts would yield more information about the Moon's crust, so it was decided that, beginning with Apollo 13, the S-IVB would be crashed into the Moon. The impact occurred at 77:56:40 into the mission and produced enough energy that the gain on the seismometer, from the impact, had to be reduced. An experiment to measure the amount of atmospheric electrical phenomena during the ascent to orbitadded after Apollo 12 was struck by lightningreturned data indicating a heightened risk during marginal weather. A series of photographs of Earth, taken to test whether cloud height could be determined from synchronous satellites, achieved the desired results. As a joke, Grumman issued an invoice to North American Rockwell, prime contractor for the CSM, for "towing" the CSM most of the way to the Moon and back. Line items included 400001 miles at $1 each (plus $4 for the first mile); $536.05 for battery charging; oxygen; and four nights at $8 per night for an "additional guest in room" (Swigert). After a 20% "commercial discount", and a 2% discount for timely payment, the final total was $312,421.24. North American declined payment, noting that it had ferried three previous Grumman LMs to the Moon without compensation. The CM was disassembled for testing and parts remained in storage for years; some were used for a trainer for the Skylab Rescue Mission. That trainer was subsequently displayed at the Kentucky Science Center. Max Ary of the Cosmosphere made it a project to restore Odyssey; it is on display there, in Hutchinson, Kansas. Apollo 13 was called a "successful failure" by Lovell. Mike Massimino, a Space Shuttle astronaut, stated that Apollo 13 "showed teamwork, camaraderie and what NASA was really made of". The response to the accident has been repeatedly called "NASA's finest hour"; it is still viewed that way. Author Colin Burgess wrote, "the life-or-death flight of Apollo 13 dramatically evinced the colossal risks inherent in manned spaceflight. Then, with the crew safely back on Earth, public apathy set in once again." William R. Compton, in his book about the Apollo Program, said of Apollo 13, "Only a heroic effort of real-time improvisation by mission operations teams saved the crew." Rick Houston and Milt Heflin, in their history of Mission Control, stated, "Apollo 13 proved mission control could bring those space voyagers back home