despite not having a second spaceship, the fire+ and - took the codes from this simulation!
thank you
enjoy!
http://iwant2study.org/ospsg/index.php/interactive-resources/physics/02-newtonian-mechanics/08-gravity/284-gravity08
[img]http://iwant2study.org/lookangejss/02_newtonianmechanics_7gravity/ejss_model_gravity08_2/gravity08_2/2015-04-17_1501s.png[/img]