SA-4 (Apollo)
SA-4 was the fourth flight of a Saturn I launch vehicle and the last of the initial test phase of the first stage. It was part of the Apollo Program.
| Mission Statistics | |
|---|---|
| Mission: | SA-4 |
| Launch: | 28 March, 1963 8:11:55 UTC Cape Canaveral LC34 |
Objectives
SA-4 was the last flight to just test the S-I first stage of the Saturn I rocket. As with the first three launches this would be a suborbital flight and would test the structural integrity of the rocket.The major addition to this flight was that to test the rockets ability to deal with an engine failure during the flight, one of the engine would be programmed to shutdown about 100 seconds after launch. If all went well the rocket would reroute the fuel for this engine to the other engines and have the rocket burn longer to compensate for the loss of acceleration. This was used successfully on the later Apollo 6 and Apollo 13 flights.
Also on this flight, the dummy second stage was outfitted with the aerodynamic design of the real second stage. This included vent ducts, fairings and dummy camera pods. And the rocket flew with antennae designed for the Block II version of the rocket.
SA-4 sitting on Pad 34
Flight
After the shortest checkout time of any rocket at 54 days, SA-4 went on to experience the longest series of holds of any mission at 120 minutes. After this SA-4 launch the last first stage only flight.The rocket operated perfectly through the first 100 seconds of the flight, when the Number 5 engine shutoff as planned. The rocket then continued to operate properly, with the propellant system rerouting the fuel to the other engines and the shutoff engine didn't disintegrate due to the heat as some had predicted due to lack of cooling propellant running around it. This was a important test proving an important feature of the clustered engine design.
The rocket reached a maximum height of 129 km and a peak velocity of 5906 km per hour. At this stage it also fired retrorockets that would be used on later mission to separate the rocket stages. On SA-4 the stages weren't designed to separate but tested the retrorockets to make sure they would fire.
