Artist concept art of the Apollo CM in re-entry mode.
On April 4, 1963, NASA was busy smacking the test version of the Apollo command module into a water tank. Engineers had plenty of data on how the Mercury single-occupant capsule reacted upon splashdown, but the upcoming Gemini flights (2-person capsule) and Apollo missions (3-person capsule) would need lots of data to ensure the safety of the astronauts.
Model of CM atop the Service Module (SM).
There were two types of impact testing to be done. Of course, the first was a water landing test, as the planned return to Earth was expected to land astronauts in the ocean. Engineers also had to plan for a possible landing on the cold hard ground. The scenario considered that in case of a launch abort, the escape tower would pull the capsule from the service module (SM) and open the parachutes. because of unpredictable wind situations, the capsule could possibly drift back over the land and smack the crew into the ground.
The CM is released from the tower.
In both cases of ground and water impact tests, picture above shows the testing procedure. High-speed cameras would film the capsule releasing from a tower (to simulate the drop velocity) against a backdrop of squares (not sure if they are painted or tiles). The squares help the engineers plot movement and impact speeds.
Recent: Orion capsule mockup in water test tank.
Recently, NASA has been developing the Orion capsule which will launch atop the giant SLS rocket (Space Launch System). The SLS is being designed as NASA's heavy-lift rocket to take heavy or large payloads into orbit or to send astronauts on missions farther from the Earth. NASA still performs drop tests to measure the durability of the craft and how well it will protect our space explorers.
In the picture above, Orion makes quite a splash. These days, motion sensors are placed on the surface points and interior structure to record stress of impact at all points. It's sort of like motion capture used by the film industry. BTW, Blogger's new method of inserting images leaves a bit to be desired. I just couldn't get the splash picture to center properly. Honestly, I tried. Grrrr.