Final answer:
Blackouts during re-entry can refer to communication loss or physical loss of consciousness due to high deceleration. A typical communications blackout lasts a few minutes, while a physical blackout from high deceleration like in a rocket sled test could last only seconds.
Step-by-step explanation:
The question of how long the astronauts experienced a blackout during re-entry could be referring to two different scenarios: the communications blackout experienced when re-entering Earth's atmosphere from space, or the physical blackout experienced by test subjects subjected to high deceleration forces.
For communications blackout during re-entry, typical durations are on the order of minutes.
As an example, during Apollo missions, the blackout period lasted for about 3 minutes.
However, for a physical blackout caused by high deceleration, the timeframe could be just a few seconds, as in the case of the rocket sled example where a test subject experienced temporary blindness after the sled came to rest from 1000 km/h in 1.1 seconds.
In the provided context, a deceleration test resulted in a temporary blackout for the test subject, which is different from the blackout period experienced during spacecraft re-entry.
However, both instances involve a loss of consciousness or communication due to extreme conditions encountered during a high-speed journey either back to Earth from space or during a high-speed test on the ground.
To calculate the deceleration of the rocket sled, a physics equation must be applied, using the given speed of 1000 km/h (which converts to approximately 277.78 m/s) and the deceleration time of 1.1 seconds.
Your complete question is: How long were they in blackout during re-entry?