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- Thread starter Wedge313
- Start date

Also, the XR-2 changes the engine thrust with the air pressure, and you will therefore see that the effectiveness of the engine (the dV) will increase as you escape the atmosphere.

That's a bit much. 4.5km/s is more typical.It seems that to get to orbit I'll need around 9.3-10 km/s..

What you need to do is put your budget in a spreadsheet and use the rocket equation to calculate each step. Then you will find the answer to how much fuel you need or what the maximum payload is for a certain mission.

Have a look at this screenshot. It's from an old spreadsheet and the numbers aren't checked, but it shows the idea. When you know 3 of the 4 parameters of the rocket equation (in black), you can calculate the missing one (in red) and use it on the next row. Note that the ISP is lower when landed to reflect the correct amount of delta-v as indicated by BurnTimeMFD.

It's an old spreadsheet I made by eyeballing the spreadsheets David and Tex used in their video's. Creating one yourself helps a lot to understand the flight plan.

Once I know your settings, I see if I can make a simple budget for a earth-moon trip and a video showing how to fly into orbit (inclusing a SCRAM ascend of course).

Once you have all the numbers and calculations right, BurnTimeMFD and a spreadsheet will match 100%.