Korbital Mechanics Lab - Delta-V

[EtherDragon]

Here is a lab I put together that explains what Delta-V is, why we need it, and how to get more of it in your rocket builds by focusing on the mathematics behind the Rocket Equation and what this equation can tell us about the benefits of using staging.

Enjoy!

[Specialist290]

Generally well-explained. Nicely done The only real quibble I have in its current form is that you mixed up escape velocity and exhaust velocity, which are two very different things.

[EtherDragon]

Generally well-explained. Nicely done The only real quibble I have in its current form is that you mixed up escape velocity and exhaust velocity, which are two very different things.

Thanks for the comment and correction! (I added a comment to the video, and blamed you for it. )

[Kulebron]

Great work. How much patience must it have taken to describe it all in this detail and simplicity!

[EtherDragon]

Great work. How much patience must it have taken to describe it all in this detail and simplicity!

Thanks. =) To me, that's the largest part of the fun for these kinds of tutorials, learning the topic well enough to describe it simply... and then apply it to my builds! I'm really looking forward to upcoming let's plays as I will be able to use this knowledge to make much better rockets.

Here's an idea - show me some before / after style images of how you guys applied the concept of staging to maximize delta-v in your builds!

[Kulebron]

See my website in the signature. You're welcome to quote it.

I gathered such a collection (on the front page) once in this thread: http://forum.kerbalspaceprogram.com/threads/51961-Post-some-of-your-huge-rockets-for-distant-missions

[Specialist290]

Since you've asked:

The "before" shot was my first Mun lander design, from somewhere back in 0.18 or so when I barely knew what I was doing:

It made it there and back, but it was an incredible hassle getting it both built and flown.

The "after" pic is from one of my more recent Mun lander designs (not Apollo-style this time):

Much more practical than that other massive monstrosity

Also, since I took all the trouble to dig it up (before rereading the original post and realizing I was looking for the wrong thing), here's an older post where I worked out the math for optimizing a payload to fit a given mission. It's only a single-stage calculation, and Kulebron covers the same subject in a little more depth on his website, but I thought it might be useful.

[AuoroP]

In answering the question why do I care, you missed the biggest in my mind: it gives you the power to plan your rocket stages.

I would have preffered if you'd used the Isp and constant version of the rocket equation because people will have seen that value in the game and and maybe even have an idea that it relates to rocket efficiency. Your example just seem to just randomly pick a exhaust velocity which doesn't help people plan better rockets. A good, but dated, example is the wiki's advanced rocket design.

I recently showed that you need a delta-v of 1500 m/s to get out of the lower atmosphere and a delta-v of 3000 m/s to get into low Kerbin orbit. Surely, being able to plan rocket stages knowing when you'll hit these two marks is a huge reason to care about delta-v. Other people have made delta-v maps that then tell you how much delta-v it will take to get around the Kerbol system.

[EtherDragon]

In answering the question why do I care, you missed the biggest in my mind: it gives you the power to plan your rocket stages.

I would have preffered if you'd used the Isp and constant version of the rocket equation because people will have seen that value in the game and and maybe even have an idea that it relates to rocket efficiency. Your example just seem to just randomly pick a exhaust velocity which doesn't help people plan better rockets. A good, but dated, example is the wiki's advanced rocket design.

I recently showed that you need a delta-v of 1500 m/s to get out of the lower atmosphere and a delta-v of 3000 m/s to get into low Kerbin orbit. Surely, being able to plan rocket stages knowing when you'll hit these two marks is a huge reason to care about delta-v. Other people have made delta-v maps that then tell you how much delta-v it will take to get around the Kerbol system.

Thanks for your comments!

I tried to mention in the video that (generally) more Dv = more capability to reach more places. 0:20 to 0:30 says on a basic level, that the sum of the things a rocket can do is reliant on its total Dv. However, it is a but unclear how that pertains to TWR, but that is covered in my other tutorial and other great ones around the net. The main purpose of this video was really to go over the math and science behind Dv in rocketry, so that people could more intuitively understand what the math is predicting. What (I hope) people learn from the video is that having simpler rockets tends to have more delta-v because the empty weight is reduced. Adding appropriate staging, especially the use of asparagus staging, really makes sense mathematically (it's not just a game glitch or exploit - it really is more efficient in most cases, and the math supports that.)

Why do you need more Delta-V? To go farther away from Kerbin.

How do we get more Delta-V? The math tells us that Fuel% and Engine efficiency only get us so far - but even these limits can be increased by staging.