Linked Questions

110
votes
4answers
18k views

What is the purpose of having a countdown during a rocket launch?

Every rocket launch has a countdown. But what purpose does it serve?
39
votes
4answers
15k views

Why didn't the Space Shuttle have a launch escape system?

Since the very beginning of space exploration, rockets had some sort of Launch Escape System (LES). From this Wikipedia article, we know that Mercury and Apollo had an escape tower, while Vostok and ...
16
votes
2answers
3k views

In the Saturn V launch sequence, what defined COMMIT, and what happened between COMMIT and LIFTOFF?

With the Saturn V, there were two critical moments during launch that I am curious about: The vehicle COMMITs to liftoff The vehicle LIFTS OFF LIFTOFF is fairly obvious: the booster has risen some ...
8
votes
2answers
2k views

What is the problem with aborting a Space Shuttle launch?

In the question Why didn't the Space Shuttle have a launch escape system? there was discussion in the commentary about why the Space Shuttle could not safely abort through much of its envelope. ...
7
votes
3answers
1k views

How far in advance are launch dates set?

We are going to visit Florida in early-mid February and were wondering if we could watch a launch. The schedule, however, does not seem to include February yet. For the purposes of planning our trip -...
8
votes
1answer
638 views

Do Blue Origin's BE-3 engines need to run for 7 seconds to "warm up"?

In the Blue Origin YouTube video Replay of New Shepard Mission 8 Livestream, "command engine start" is heard at T- 00:03, an audible "pop" can be heard at about <...
6
votes
1answer
435 views

Simulating launch velocity of falcon 9

Help! I finished my numerical simulation of falcon 9 launch in google sheets, where I calculate all the value changes with time. But, when I looked at real launch to compare the values, I got really ...
3
votes
1answer
572 views

Why doesn't Ariane-5 lift off at T=0 seconds?

I have seen Ariane-5 lift off at T+07 seconds and not at (or close to) T=00 seconds. The following statement is from the Ariane-5 User's Manual (Page 35, Section 2.3 - Typical Mission Profile): The ...
5
votes
1answer
177 views

What specific event determined the "end" of a shuttle mission?

We've had several questions about when a mission officially "begins". But what about when a mission officially "ends"? The Apollo Flight Journal stops the mission clock at splashdown. What was the ...
1
vote
0answers
82 views

What happens at T-0 for the SpaceX Starship?

Every launch system defines a different event for T-0. The SpaceX Starship prototypes seem to ignite the engines at T-1.0 and accent seems to begin between T+1.0 and T+1.5. An overthrust abort for SN-...