# Tag Info

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### What does ln mean in the Delta V equation?

ln is a math function, the "natural log" Most scientific calculators have a key for it. See https://en.wikipedia.org/wiki/Natural_logarithm
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### Why do some rockets not ignite all their engines during liftoff? (GSLV MK3 LV)

Besides limiting aerodynamic stress and drag losses as you and Antzi mention, using the core engine only at high altitude means the engine can be optimized for low-pressure use by putting a larger ...
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### How to account for burned fuel mass when calculating spacecraft acceleration?

The quantity you ultimately need when planning your manoeuvre is change in velocity, which in spaceflight terminology is called delta-v, $\Delta v$ (searching this term would give you a lot of ...

### Payload capacity of a rocket

The short answer is: Tsiolkovsky rocket equation. You need some velocity to achieve some position (an orbit or a body) in space. Farther a position - more velocity. More velocity - more propellant ...

### Why do some rockets not ignite all their engines during liftoff? (GSLV MK3 LV)

Your assumption that we need max thrust at takeoff is partially wrong. Although right at takeoff you do want max thrust, it might be counterproductive short after: Your rocket and payload are Max G ...

### How much thrust needed to move 6,000 kg from LEO to Lunar Orbit?

What is needed is not thrust (above a certain basic amount), but delta-v, a function of the type of engine and the ratio between fueled mass and dry mass, according to the Tsiolkovsky equation. The ...
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### How much fuel is necessary to cause delta-v?

The Tsiolkovsky rocket equation tells you how much delta-V you get for a given exhaust velocity and full/empty mass ratio per stage. Typically you'll want to divide the total 9400m/s requirement into ...

### Payload capacity of a rocket

It perhaps become clearer when stating what rockets do. They change velocity. In space terms, that's delta-v. A rocket stage can only change your velocity some limited amount. Different targets in ...