Fastest Rocket EVER

If you watch 'Destination Moon', you'll notice that the rocket reaches moon in just a minute and 21 seconds.

If we allow 10 seconds for the rocket to reach its full speed, it goes to the moon in 1 minute and 11 seconds. That's 71 seconds.

Now, the shortest distance to the moon is around 356500 kilometers, so the rocket is the fastest thing in existence.

It can travel around 5021 kilometers per second. Not per hour, but per SECOND. This would mean it travels at 301268 kilometers per minute and 18076056 kilometers per hour.

And people say this is 'realistic', because Herge researched things a lot for this?

What is so realistic about a Earth-made rocket traveling at over 18 million kilometers per hour?