Saturn V acceleration

[Allan F]

How fast was the Saturn V accelerating from the launch pad and to orbit? What was it's velocity at "tower clear"?

[Zakalwe]

Apollo by the Numbers gives a lot of this info:

http://history.nasa.gov/SP-4029/Apollo_18-20_Ascent_Data.htm

And Bob's excellent page will also help:
http://www.braeunig.us/apollo/saturnV.htm

[Bob B.]

The following is from a simulation, but it mirrors almost exactly what the real graph looks like:



It was roughly accelerating between about 1.2 and 1.3 g during the time that you ask about.

 

[Allan F]

Someone somewhere quoted a speed of 100 km/h at tower clear, which I don't think the Saturn V did.

[Glom]

What's EMR shift?

[Bob B.]

What's EMR shift?

EMR = Engine mixture ratio.  The J-2 engine had a valve that could control the flow of LOX to the combustion chamber.  By closing down the value and reducing the flow of LOX, the mixture ratio could be changed from 5.5:1 to 4.5:1.  Since this reduced the mass flow rate to the engine, it also reduced the thrust.  This valve was part of a propellant utilization subsystem, the purpose of which was to monitor and control the flow rates to make sure the fuel and LOX supplies where depleted simultaneously.  The "EMR shift" was the moment this value changed positions.  It shows up on the acceleration graph because of the decrease in thrust that resulted.

[Allan F]

What's EMR shift?

They changed the fuel/oxidizer ratio.

[Bob B.]

Someone somewhere quoted a speed of 100 km/h at tower clear, which I don't think the Saturn V did.

That sounds pretty close.  According to my simulation, it would be traveling about 25 m/s, or 90 km/h.

[Allan F]

The faster the better. Didn't look that fast on the little screen though. Must be because it is mentally difficult to grasp the SIZE of that machine.

[AstroBrant]

Someone somewhere quoted a speed of 100 km/h at tower clear, which I don't think the Saturn V did.

I also saw somewhere that it was 60 mph when it cleared the tower. So that's about the same. One is intuitively struck by how slow it appears to be moving, but that is an illusion based on failing to sense the enormity of the craft. I have noticed with ships and large planes how they always seem to be moving slower than they are.

[Bryanpoprobson]

Just by eye, one thing I noticed in being an avid launch watcher, The Shuttles acceleration from the launch pad seemed noticeably quicker than the Saturn V. Is this just my eye or a fact? I should look back over the launch videos and time it.

[JayUtah]

Just by eye, one thing I noticed in being an avid launch watcher, The Shuttles acceleration from the launch pad seemed noticeably quicker than the Saturn V. Is this just my eye or a fact? I should look back over the launch videos and time it.

I don't believe that's just your eye.  The shuttle fairly leaps off the pad and is generally going in excess of 140 km/h when it clears the tower, according to one of the press kits.

[Echnaton]

Watching the films from the highest tower cameras give and idea of how fast the S5 was going.   A few seconds after the slow start, those fins at the business end of the rocket just zoom by.

[Bob B.]

The Shuttles acceleration from the launch pad seemed noticeably quicker than the Saturn V. Is this just my eye or a fact?

It's a fact.  The Shuttle's thrust-to-weight ratio at liftoff was considerably more than the Saturn V -- about 1.7 for the Shuttle vs. 1.2 for Saturn V.

[Allan F]

The tower for the shuttle launch was much shorter too.