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Friday 25 May, 2018

# Comment #3678082 by Tom Kenny

Apr 15th 2015, 9:37 AM #

Genuinely thank you, I do understand how orbits work, It was just that I didn’t think it would be so hard to escape the gravitational pull of the earth. I imagined you could (easily) keep increasing momentum say for the first 3 years in a straight line and then alter the direction of the satellite using the motor to enter an orbit in the last six months of the journey. From your kind explanation I understand that the gravitational influences are much greater than I imagined, thank you again

### An Irish company's product will become the closest man-made object to the Sun

All going to plan…

## REPLIES

Apr 15th 2015, 9:52 AM

Theoretically you could but with the types of engine we have at the moment, anything that could produce that degree of acceleration and deceleration would require an enormous amount of fuel to be carried. More fuel means more weight, more weight means more inertia, more inertia means more acceleration / deceleration needed to overcome inertia, more acceleration / deceleration means more fuel means more weight means more inertia and so on. There are new engines being developed and some in use that don’t use rocket propellant and so the weight problems aren’t as pressing but they can’t at the moment as far as I’m aware produce the same degree of thrust as a conventional rocket. So while they can thrust and accelerate for longer without running out of fuel, they can’t accelerate as fast. Think of it as like a sprinter versus a marathon runner.

Apr 15th 2015, 10:27 AM

Tom, escape velocity of the earth is 11.2 km/s, you must reach that speed to escape earths gradational pull. As Ronan said this is most efficiently done by flying at an angle to the earth once you get into the upper atmosphere. Once you get far away from earth that the earths influence becomes negligible you will fall into the sun in a spiral.

The closer you get to the sun the higher velocity you require to stay in a stable orbit. (elliptical or circular) This is why the inner planets have shorter (years) than the other planets.

A satellite desiring a close stable orbit to the sun will be required to speed up as it gets closer to the sun. It needs to reserve all its fuel for this. Fly bys can also assist. Actual travel from here to the sun is done under the influence of gravity. By the same reasoning satellites visiting the outer planets like to use aero-breaking to slow down.

Apr 15th 2015, 6:26 PM

Kerbal space programme. That is all