Newbie question - why can't I replicate the Basic Flight Training

[lloyd709]

I'm just starting out and so completed the Basic Construction and Basic Flight Training.  I thought though before going on I'd replicate the rocket in Sandbox mode and try to vary some parameters and get a feel for the differences they make.    But when I replicated the rocket (using the MK1 Command Module, MK16 Parachute and RT-5 Flea engine,  checking that all the parameters were the same as in the Basic Flight Training) I found the rocket I built with the sandbox climbed to an altitude of 22,850 meters  whereas the one in the Basic Flight Training only climbed to 14,226 metres!!  Interestingly the thrust and duration of the engine were identical between the two so I have no idea why one would go higher than the other.  I'm now struggling to continue without understanding what's going on here!

Can anyone give me any pointers?

[VoidSquid]

Long story short: the tutorials are not that good, better: build and launch your own contraptions! And for questions, just ask your fellow Kerbonauts.

Longer answer: the tutorials, the more versions are between them and the current KSP version, the more they are "off". Which includes physics, dv, etc. You just experienced yourself.

[Spricigo]

Nothing much to add to @VoidSquid explanation.

The same goes for form posts, videos tutorials and guides out there, take in account how old the thing is. Some have aged pretty well, but other turned in complete nonsense.

 

[Popestar]

Heck, you can apply all of this to flights in the same game with the same builds.  I have craft that fly straight as an arrow one flight, and then wouldn't know a straight line if it bit them on the next.

[swjr-swis]

14 hours ago, lloyd709 said:

Can anyone give me any pointers?

Introducing one of my nephews to the game just a few days ago, I encountered the same thing: a direct replica of the starting rocket went so high so fast it would shred its parachute to bits on the way back down.

I relaunched with a triplet of basic winglets rotated by 5 degrees and SAS off, so it would lose speed by rotating - problem solved and parachute opened safely. Nephew seemed to find it hilarious that the only way to survive was in a vomit rocket. For my next trick...

[Wobbly Av8r]

The truth of the matter is that, for whatever reason, the Cd of Flea in the tutorial is around ~0.23 and in game (Sandbox), the Flea Cd is ~0.04, a difference of more than 5x. (For those unfamiliar, the amount of aerodynamic drag on an object increases exponentially with airspeed, taking into account air density, multiplied by the Coefficient of Drag (Cd) which is mathematically how the shape of the object influences the amount of drag).

This is always good to remember when someone complains such-and-such isn't 'realistic'... it is what the program says it is -- not reality -- despite the attempts to make them similar.

[OHara]

Yes, Squad did change the shape of the 'Flea' booster, leaving the old shape in the game for compatibility with old saves, and old tutorials.

[lloyd709]

Thanks everyone for getting back on this.  I've read through all the posts - and the posts on the original thread on this problem that I didn't find before -  and now understand the cause and a bit more (like the importance of  Coefficient of Drag!  Thanks again.