Altaïr
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Ok, I'll try to make a detailed explanation without entering into mathematical stuff.
Delta-V is to be understood as "velocity change". Basically, you can see it as a rocket's resource, its delta-V is "by how much it can change its velocity". For example, if your ship is in LEO ("LEO" stands for "Low Earth Orbit", let's assume its speed is 1655 m/s) and has 1000 m/s of delta-V at its disposal, it means that by burning prograde, it can increase its speed up to 2655 m/s. Of course you can also decrease your speed by burning retrograde. In this case, you can lower your speed down to 655 m/s.
Also, note that those delta-V considerations are not valid for the lift-off phasis. In this reasoning, we assume that we fight neither gravity, nor drag. So it's valid in space, but not for lift-off. For example, the orbital speed in LEO is 1655 m/s, but a rocket starting from the pad that has 1655 m/s can't make orbit. Because it has to fight gravity and drag. It's current to assume that a rocket needs around 2800-3000 m/s to make orbit, though it depends on several parameters.
Apart from the lift-off phasis, the delta-V map tells you how much delta-V you need to go to a given destination. There is an example in the first post that shows a trip from LEO to Low Moon Orbit.
Now you may ask, how do you know how much delta-V a rocket has at its disposal? A simple answer is: the more fuel it has, the more delta-V it has. The same as a car can travel over a greater distance with more fuel in its tank. Now if you want to calculate it accurately, there are some spreadsheets available for this. Here is mine:
https://docs.google.com/spreadsheet...zOEbB5pSJMOjeiR-ES4y0HOzxy8/edit?usp=drivesdk
It's in read-only mode, you have to make your own copy to use it.
For example if you want to calculate the delta-V for this ship:
You have to enter its characteristics that way:
There's a green dot over each field you have to modify. In the upper left part, fill the number of each engine used. In this case we have one Broadsword. Then on the right, specify how much fuel you have. In this case, there's one 20 tons fuel tank, so I entered 20 (that's actually 2 tons for the empty tank and 18 tons of fuel, but you just have to enter the global mass, the spreadsheet takes this automatically into account). Finally, below is the mass that doesn't come from engines and fuel tanks. In this case, there's a capsule and a parachute, so it's 4.5 tons.
And that's all, you can read the result below. Especially, its delta-V is 3030 m/s.
My spreadsheet is designed to be simple to use, but the drawback is that it works for only one stage. Other spreadsheets are more complete and can make calculations for multi-stage rockets (the one from Horus Lupercal for example).
With all of this, you can plan accurately your space trips. The delta-V map tells you how much delta-V you need, the spreadsheet tells you how much you have.
Delta-V is to be understood as "velocity change". Basically, you can see it as a rocket's resource, its delta-V is "by how much it can change its velocity". For example, if your ship is in LEO ("LEO" stands for "Low Earth Orbit", let's assume its speed is 1655 m/s) and has 1000 m/s of delta-V at its disposal, it means that by burning prograde, it can increase its speed up to 2655 m/s. Of course you can also decrease your speed by burning retrograde. In this case, you can lower your speed down to 655 m/s.
Also, note that those delta-V considerations are not valid for the lift-off phasis. In this reasoning, we assume that we fight neither gravity, nor drag. So it's valid in space, but not for lift-off. For example, the orbital speed in LEO is 1655 m/s, but a rocket starting from the pad that has 1655 m/s can't make orbit. Because it has to fight gravity and drag. It's current to assume that a rocket needs around 2800-3000 m/s to make orbit, though it depends on several parameters.
Apart from the lift-off phasis, the delta-V map tells you how much delta-V you need to go to a given destination. There is an example in the first post that shows a trip from LEO to Low Moon Orbit.
Now you may ask, how do you know how much delta-V a rocket has at its disposal? A simple answer is: the more fuel it has, the more delta-V it has. The same as a car can travel over a greater distance with more fuel in its tank. Now if you want to calculate it accurately, there are some spreadsheets available for this. Here is mine:
https://docs.google.com/spreadsheet...zOEbB5pSJMOjeiR-ES4y0HOzxy8/edit?usp=drivesdk
It's in read-only mode, you have to make your own copy to use it.
For example if you want to calculate the delta-V for this ship:
You have to enter its characteristics that way:
There's a green dot over each field you have to modify. In the upper left part, fill the number of each engine used. In this case we have one Broadsword. Then on the right, specify how much fuel you have. In this case, there's one 20 tons fuel tank, so I entered 20 (that's actually 2 tons for the empty tank and 18 tons of fuel, but you just have to enter the global mass, the spreadsheet takes this automatically into account). Finally, below is the mass that doesn't come from engines and fuel tanks. In this case, there's a capsule and a parachute, so it's 4.5 tons.
And that's all, you can read the result below. Especially, its delta-V is 3030 m/s.
My spreadsheet is designed to be simple to use, but the drawback is that it works for only one stage. Other spreadsheets are more complete and can make calculations for multi-stage rockets (the one from Horus Lupercal for example).
With all of this, you can plan accurately your space trips. The delta-V map tells you how much delta-V you need, the spreadsheet tells you how much you have.