How to determine how much delta V required for a flight?

[jarmenia]

So I've found the delta V maps and those are great and all, but how can I determine how much delta V I need if what I am doing isn't on the charts? For example, how much delta V is required to go from an 80 km orbit to a 4,000 km orbit? How can I fill in these blanks?

Thanks

Edited February 5, 2014 by jarmenia

[Tank Buddy]

[fireflower]

If you're already at a circular 80 km orbit, look at your navball for your orbital velocity.

Calculate, using the basic algebra of the helpful video posted above, the velocity of a 4000 km orbit of Kerbin. Keep in mind that the values for Kerbin and Earth are very different.

Subtract one from the other. That is the ÃŽâ€v you need to go from 80 to 4000 km orbit.

Burn prograde to raise your apoapsis to 4000 km. Then wait until you are at your new 4000 km apoapsis and burn prograde to raise your periapsis to 4000 km as well.

[jarmenia]

This link is taking me to a video with some cartoon that doesn't seem to be related to the question.

[fireflower]

This link is taking me to a video with some cartoon that doesn't seem to be related to the question.

That is because you don't have the patience to watch it for more than 7 seconds. It is a Scott Manley video in which he teaches the answer to the very problem you have asked.

[jarmenia]

That is because you don't have the patience to watch it for more than 7 seconds. It is a Scott Manley video in which he teaches the answer to the very problem you have asked.

Actually no, the link on my phone takes me to a completely different video, I'm not sure why since I watch many of Scott's video's on my phone. If I watch it on my computer I see it's the correct one. Thanks for the link though.

[MarvinKitFox]

You can always use the maneuver nodes to see delta-v needs.

Start at 80, maneuver up to 4000, maneuver to 4000-circular. sum the two delta-v displayed.

If you arent at the desired start point, just add another two nodes that take you there, first.

[jarmenia]

You can always use the maneuver nodes to see delta-v needs.

Start at 80, maneuver up to 4000, maneuver to 4000-circular. sum the two delta-v displayed.

If you arent at the desired start point, just add another two nodes that take you there, first.

I thought of that but the idea is to know how much delta v to put into the rocket before I launch so I can complete the desired task wwithout having too much unnecessary mass.

[rkman]

never mind, already answered.

[ShadowDragon8685]

My advice would be not to swear the exact amounts, and don't try to cut your fuel reserves down to the wire. It's better to have extra and not need it than to need it and not have it.

So if you're trying to to go from a Low Orbit of roughly 70Km to a 4,000Km orbit, sum up the dV you'd need to go from 70 to Kerbin Escape, which is 950 if I'm reading the DV map correctly. Add a fudge factor to that in case you need to do some corrections mid-flight or suddenly develop a need to head home. I'd say round it up to the nearest multiple of 100 and then add 20% just to be safe, so pack whatever stage you're using to get there with about 1,200 dV, and Bob's your uncle.

No, not that Bob. The other Bob. There's a lot of Bobs.

[fireflower]

I say just go to wikipedia on rocket science or the ksp wiki on rocket science and just calculate the ÃŽâ€v difference in orbits yourself. It's just algebra. You can do it in Excel or FOSS equivalent or even using the scientific calculator that shows up on Google if you google "scientific calculator."

[jarmenia]

Thanks for all the suggestions. I watched the video by Scott Manley and built a spread sheet. Based on my test flights it's working correctly and I am able to predict with confidence now how much delta v I need to pack onto my rockets. How do I mark this thread as answered?

[Padishar]

Edit your first post and you can change it in there (it may be in advanced view).