Helping Vehicle

*Back to Building (Overall)*
**Helping vehicles** are used to help other space vehicles reach their destination. They are used when the main rocket does not have enough fuel, in case of a malfunction or when a rocket fails to do an engine burn when it should.

Helping vehicles usually are unmanned.

## Basic helping rockets

These rockets can be built within the basic, free game.

### Earth

The Mercury return mission or the Venus return mission requires huge amounts of fuel and no room for errors. Some players managed to build a separate launch vehicle, move it near the launch pad, then fly a second rocket above it. The helping vehicle gives an additional thrust and can push the second rocket out of Earth's atmosphere.

**Warning:** To place one rocket above the other requires a lot of patience. It is very difficult, because of Earth's powerful gravity. Use "No Gravity" settings and RCS to ease the process.

### Earth escape

To save some fuel, you can set a rocket in low Earth orbit. The helping rocket can come close and start pushing the main rocket. This requires patience and the use of RCS Thrusters.

### Venus

*See also:*
This is a difficult mission, suitable for Venus. No other planet needs this kind of help.

The helping rocket lands first. The main rocket will land on top of it. When the mission is over, the helping rocket fires its engines and helps the main rocket reach a higher altitude, where the atmosphere is not so dense. From there, the main rocket must fly on its own, to reach orbit.

This kind of mission is very difficult. The main rocket needs to land exactly on top of the helping rocket, a very difficult task. In order to land, the main rocket needs to do as follows:

1. Enter Venus's sphere of influence.
2. Gain a highly elliptical orbit by aerocapture.
3. Fire the engine at apoapsis, to gain a high Venus orbit.
4. When the main rocket is above the helping rocket on its orbit, fire the engines to slow down and reach a direct impact trajectory, towards the helping rocket.
5. From time to time, Trajectory Correction Maneuvers are needed, both above and inside the atmosphere.
6. After parachutes are deployed, with the help of RCS Thrusters or the engines, adjust the trajectory to fall right on the helping vehicle.

In addition, the helping vehicle might have wheels, to move itself to the best place.

Alignment is redundant if the rockets dock to each other on landing.

### In orbit around other celestial bodies

A helping rocket in orbit around other planets can be useful to push a rocket into a solar orbit, to reach Earth. You will need to bring the helping rocket from Earth.

### Earth landing

*See also:*
This is something nobody likes. A rocket managed to visit another planet, returned to Earth and entered Earth orbit but has no fuel left to land. The solution is to bring in another rocket to push it to land safely.

Another problem occurs when the rocket that needs to be rescued has no parachutes. In this case, it is possible to build a rescue rocket that will land together with the capsule it has rescued.

## Docking

A helping vehicle can dock to the rocket it's helping. Both rockets will need an exposed Docking Port during their rendezvous.

### Refuelling

Starting with version 1.35, helping rockets can dock to and refuel a rocket, that will then continue its mission. Until version 1.4, this required the full version to be purchased. In 1.5, the smaller docking port is free, but the big ones are required the Parts Expansion purchase.

## Surface rescue

A helping vehicle can be docked to an existing rocket on a celestial body's surface, to aid in reorbiting or transfer fuel. This is easier on the moons of Mars, because of their small size.

## Problems

The use of undocked helping rockets is very difficult, because it requires patience and difficult maneuvers.

When time warping, physics are disabled, meaning that one rocket can pass through the other. This can sometimes happen without time warp if they aren't docked together.