tag:blogger.com,1999:blog-2675974463524895416.post8828034058570308905..comments2024-03-28T01:06:18.986-05:00Comments on An Ex Rocket Man's Take On It: Non-Direct to the Moon with 2020 StarshipGary Johnsonhttp://www.blogger.com/profile/06723964751681093047noreply@blogger.comBlogger9125tag:blogger.com,1999:blog-2675974463524895416.post-75053337083267772902020-07-19T10:05:02.054-05:002020-07-19T10:05:02.054-05:00Rok: Take a look at the 7-18-20 update appended t...Rok: Take a look at the 7-18-20 update appended to the article. I looked at your idea, and found it feasible, and comparable, to refueling in LLO before the descent. It is a two-tanker scenario, you cannot do it with one. Three vessels must depart simultaneously. -- GWGary Johnsonhttps://www.blogger.com/profile/06723964751681093047noreply@blogger.comtag:blogger.com,1999:blog-2675974463524895416.post-23910233566805731972020-07-18T15:51:53.359-05:002020-07-18T15:51:53.359-05:00To clarify. Theres a fully fueled tanker and fully...To clarify. Theres a fully fueled tanker and fully fueled starship in leo, same orbit, physically within say 10km. <br /><br />They both do trans lunar injection burns at the same time. <br /><br />Wouldnt they end up in a simmilar enough trajectory for the tanker to be able to match and dock with low dv usage? <br /><br />It does take 3 days to get to the moon.<br /><br />Abort could be at any time before elliptical orbit reaches lunar sphere of influence, after that it has to be a free return trajectory. <br /><br />Actually, refueling in LLO has less abort options. Rokhttps://www.blogger.com/profile/01594627296669652306noreply@blogger.comtag:blogger.com,1999:blog-2675974463524895416.post-20760872986340611012020-07-18T09:00:11.407-05:002020-07-18T09:00:11.407-05:00I haven't thought about that scenario before. ...I haven't thought about that scenario before. Both vehicles would have to depart simultaneously from LEO in order to be "pre-rendezvoused" to make it work. There would have to be some sort of abort in case this simultaneous departure failed. It's lot easier to handle the rendezvous without the simultaneous time constraint, if you do it in a closed, short-period orbit situation, one circular, one elliptical, sharing either a periapsis or an apoapsis. -- GWGary Johnsonhttps://www.blogger.com/profile/06723964751681093047noreply@blogger.comtag:blogger.com,1999:blog-2675974463524895416.post-23252862962554320022020-07-17T00:42:41.067-05:002020-07-17T00:42:41.067-05:00I mean departing from LEO. I mean departing from LEO. Rokhttps://www.blogger.com/profile/01594627296669652306noreply@blogger.comtag:blogger.com,1999:blog-2675974463524895416.post-10772908442909108952020-07-17T00:40:37.529-05:002020-07-17T00:40:37.529-05:00This comment has been removed by the author.Rokhttps://www.blogger.com/profile/01594627296669652306noreply@blogger.comtag:blogger.com,1999:blog-2675974463524895416.post-55566294142604431832020-07-16T12:53:19.133-05:002020-07-16T12:53:19.133-05:00Then I do not understand what it is that you propo...Then I do not understand what it is that you propose. A tanker flying by the moon and a cargo craft launching from the moon have NOT rendezvoused. Nor can they, <br /> excepting by a launch timed and a burn timed to the exact second. Putting them on the same trajectory toward Earth does NOTHING to effect such a rendezvous, so the 3 day travel time is irrelevant to that picture. You have to be within a couple of miles, not hundreds of km, to just "thruster" your way together. Sorry, that's just orbital mechanics. -- GW<br />Gary Johnsonhttps://www.blogger.com/profile/06723964751681093047noreply@blogger.comtag:blogger.com,1999:blog-2675974463524895416.post-50069522251924568602020-07-16T04:07:43.119-05:002020-07-16T04:07:43.119-05:00How feasible/infeasible are multiple spacecraft pe...How feasible/infeasible are multiple spacecraft performing the same departure burns while being say a few kilometers apart?<br /><br /><br />Its more of a software / navigation problem than hardware. <br /><br />Coast phase is 3 days , Apollo program did an undocking, docking during that time. <br /><br />Then again, it only reduces fuel requirements to LEO by a couple hundred tons. Rokhttps://www.blogger.com/profile/01594627296669652306noreply@blogger.comtag:blogger.com,1999:blog-2675974463524895416.post-86198261604842286642020-07-15T13:05:31.585-05:002020-07-15T13:05:31.585-05:00If I understand your intent correctly, you want t...If I understand your intent correctly, you want to refuel not in LLO but on the free return to Earth. The timing of the launch to enable the rendezvous would be extremely critical. You could not even be a couple of minutes off. Being able to rendezvous reliably is why I did it in LLO, and also why I put a rendezvous budget on the tankers. It takes a difference in orbital periods to accomplish. -- GW<br />Gary Johnsonhttps://www.blogger.com/profile/06723964751681093047noreply@blogger.comtag:blogger.com,1999:blog-2675974463524895416.post-62871372307353197472020-07-15T06:36:19.601-05:002020-07-15T06:36:19.601-05:00If im calculating it right.
120t starship needs ...If im calculating it right. <br /><br />120t starship needs to be 280t on the moon, to get back to earth. <br /><br />With 150t of additional payload, it needs to be 910t from earth escape to land on the moon. <br /><br />With full 1200t of fuel and 150t payload from LEO, it still weighs 600 at earth escape. S<br /><br />it needs 310t of fuel. <br /><br />How about one tanker on a free return trajectory?Rokhttps://www.blogger.com/profile/01594627296669652306noreply@blogger.com