Have you ever wondered what it takes to get a spacecraft off the Earth and into space. And how managers at NASA can actually navigate a spacecraft to another planet? And how does a gravity assist work? And how do they get them into orbit? And how do they land? So many questions…

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Hello Fraser and Pamela and Rebecca,

Love the podcast... your efforts have educated, entertained and enlightened me for many hours over the last few months... many many thanks.

In the 'getting around' podcast I think you might have missed mentioning a rather good subtopic.... rendezvous in orbit.

I may have it wrong, but I believe that if you took a random, middle-aged, thinks-he-is-a-great-driver... (me! me!..... take me!!).... and stuck him on a rocket broomstick in a orbit a few minutes behind the ISS and said ok mate.. drive over to the airlock... he would be in all sorts of trouble.

Unless I have my facts wrong, nearly everything he needs to do with his rocket is counter-intuitive... he needs to reverse orientation and fire a braking thrust to lower his orbit.... come up under and in front and then fire a accelerating thrust to lift and match orbits... and he needs to massively think ahead and act early for all his fine controls. Sounds like fun.

I can imagine the conversation Fraser and Pamela could have on this topic and I bet it would be worth listening to... As I say, I could have my facts wrong... but I thought it might be worth mentioning.

Best regards and thanks again,
Walruslike

I have not studied celestial mechanics, but I believe I know enough about the basic priniciples to answer your question.

Suppose you and the ISS are in coplanar circular orbits around the earth and you want to dock with it. To minimize fuel consumption, you should need to do this via an elliptical transfer orbit with appropriate apigee (high) and perigee (low) points. To enter the transfer orbit, you would need to use your thruster briefly to increase your speed to that for the transfer orbit just as you reach the transfer orbit. The transfer orbit would need to cross the ISS's orbit just as the ISS was passing the crossing point, On reaching the ISS's orbit, you would need to use the thruster again to decrease your speed to match the speed of the ISS. Identifying the appropriate time and thrust for entering the transfer orbit and the approprirate thrust to use in leaving it would be laborious without use of a computer.