Mechjeb - What is Q?

[Gooru]

there is a new option in Mechjeb

limit Q to [20000] pa

what does this mean?

[Harry Rhodan]

Dynamic pressure.

[MaverickSawyer]

It's the magical (and somewhat evil) entity that tears off antennas and solar panels when you go too fast. Dr. von Kerman tells me that it's an exceptionally ticklish being, which is why the more delicate stuff breaks off first.

(Harry's got the actual answer, though, if you're looking for a real-world description. )

[Ten Key]

If you've ever watched or listened to the audio from a launch, you'll hear them talk about the rocket being at "Max Q". It's the point in the flight where the dynamic pressure on the rocket peaks.

[Korizan]

As the question has been answered on what it is, lets deal with the follow on.

What would I use it for.

Well I have been thinking about that and it could be A LOT more useful then limiting your acceleration (I currently limit mine at 20m/s for rockets)

Instead you would set your max q (number still needs to be figured out) to something that would prevent your ship from burning up on accent.

This in theory would be a incredible boon to SSTO's.

Planning on doing some testing at some point to figure out if it works like I think it will.

Edit - After some testing (no Guarantees) it looks like setting your Max Q to 50,000 fits the bill for SSTO's.

Edited November 15, 2015 by Korizan

[Seaview123]

For me, it helps out a lot with rockets that aren't perfectly streamlined or have large fairings. Setting the Max Q in MechJeb automatically throttles down when the aerodynamic pressure gets too high, then throttles back up when I'm out of the thicker parts of the atmosphere. I had been using the "limit to terminal velocity" feature, but the default Q setting (20,000) seems to work much better.
One thing to be careful of... when I set it in the Launch Assistant, MechJeb set the default Q on for everything. I learned that trying to get a spaceplane to orbit and it took me a while to figure out it was MJ that was throttling back when I tried to go hypersonic.

[Korizan]

[quote name='Seaview123']For me, it helps out a lot with rockets that aren't perfectly streamlined or have large fairings. Setting the Max Q in MechJeb automatically throttles down when the aerodynamic pressure gets too high, then throttles back up when I'm out of the thicker parts of the atmosphere. I had been using the "limit to terminal velocity" feature, but the default Q setting (20,000) seems to work much better.
One thing to be careful of... when I set it in the Launch Assistant, MechJeb set the default Q on for everything. I learned that trying to get a spaceplane to orbit and it took me a while to figure out it was MJ that was throttling back when I tried to go hypersonic.[/QUOTE]

There is a "Utilities Button" in Mechjeb, and I believe all of those items are persistent and includes items like max Q, Acceleration, even Staging.
Quick and easy place to check and see if you left something on, or engage a single function for that matter.