New Scott Manley vid explains how to manually calculate TWR etc.

[Langkard]

Scott Manley recently posted a new vid which explains how to manually calculate TWR, Isp, Delta-V, etc using a spreadsheet. It isn't in-depth and is meant mainly for those who are curious about the common rocket equation terms and/or what it is exactly that Kerbal Engineer is calculating to get to the final numbers.

https://www.youtube.com/watch?v=zLitRxZMsSc

Warning:

The video is not meant, I assume, for people who already know how to do the calculations by hand or don't care about them. It seems rather pointless, then, for anyone to complain in this thread about that.

If you don't like Scott Manley's vids, don't bother complaining about that either. It clearly states it's his vid in the title. No one forced you to click on the link. So no manufactured drama needed.

Also, be aware that this video assumes you know how to do math, are competent enough to look up the equations for yourself on the internet if needed and that you know how to use the pause and rewind capabilities of YouTube if you didn't catch something he said or displayed completely.

[IronSides]

lol

[CaptainPep]

ALL HAIL THE MATHEMATICAL POWERS OF SCOTT MANLEY!!!

[Just Jim]

Oh My....... I SOOOOOOOOOOOO need to watch this!!!
Thank you!!!!

[MAD]

My own spreadsheet - ∆v, TWR, Burn time
{LINK REMOVED}http://www.mediafire.com/view/495l728y71ltgso/Delta-V.xlsx
not just the numbers but the math behind the numbers

[Langkard]

Nice! I like that.

[Barking Sands]

Already ahead of the OP on this one; I love Scott Manley's vids. I really liked the bit at 11:30 to 12:40. I personally prefer equivalent exit or effective exhaust velocity over specific impulse when calculating delta-V.

I never knew you could simply divide engine thrust in kiloNewtons by mass flow rate in Tons/sec to determine effective exhaust velocity in m/s. That is really handy to have in my brain's toolbox. It is pretty elegant how the equations work out cross-checked using ISP (seconds) * G (9.81 m/s^2) = F (kN) / Mdot (Tons/sec).

I already read the page on the ideal rocket equation at NASA's page here:
http://exploration.grc.nasa.gov/education/rocket/rktpow.html
... which is way more informative than the wiki entries in my opinion. But still, Scott Manley had more to add that would have helped me out had I known it sooner. Geez that guy; is there anything KSP-related that he CAN'T do??

[CaptainPep]

My brain just derped out when i read the message above.
Brain:Insuficent RAM to read message

[MAD]

Originally posted by wlayton27:

I already read the page on the ideal rocket equation at NASA's page here:
http://exploration.grc.nasa.gov/education/rocket/rktpow.html

try
http://hyperphysics.phy-astr.gsu.edu/hbase/rocket3.html
http://hyperphysics.phy-astr.gsu.edu/hbase/rocket.html#c2

[Barking Sands]

Originally posted by MAD:

Originally posted by wlayton27:

I already read the page on the ideal rocket equation at NASA's page here:
http://exploration.grc.nasa.gov/education/rocket/rktpow.html

try
http://hyperphysics.phy-astr.gsu.edu/hbase/rocket3.html

Fun. I put in my personal favorite setup of ballistic missile as best I could remember:

Veq: 2500 m/s
Mdot: 450 kg/s
F: 1,125 kN
M1: 5000 kg
M0: 165000 kg
T: 355.555 sec
U: 5256.824 m/s

That missile should be able to put a 5 ton payload into a near LEO trajectory so the payload could propel its own way into orbit without leaving staging behind as orbital debris. The end result given by HyperPhysics doesn't even show near-orbital speeds because it's just looking at burn time and gravity as a reduction in delta-V. During a gravity turn, the (-gt) isn't as straight-forward -- literally. :)

[MAD]

Originally posted by wlayton27:

During a gravity turn, the (-gt) isn't as straight-forward -- literally. :)

true, but it is the only version of the rocket eqn I have seen that has a term for planetary launch