It worsens it, LEO is around 4 km/s faster the LMO and your deeper in the suns gravity well too, all of that makes for a higher Oberth effect and higher velocity at infinity.
Fewer pieces, fewer steps.
Quote from: Impaler on 09/18/2016 09:17 pmIt worsens it, LEO is around 4 km/s faster the LMO and your deeper in the suns gravity well too, all of that makes for a higher Oberth effect and higher velocity at infinity.However, refuelling in Mars orbit changes these assumptions. Launch into LEO (or HEO), refuel in LEO (or HEO), launch to Mars, aerobrake into Mars orbit (not surface), refuel from Mars ISRU prop launched into LMO (or HMO) by tugs...Creating fuelling stations at each stepping stone breaks the rocket equation and changes our normal assumptions of spaceflight "efficiency".
That sounds very inefficient, your scrubbing speed at mars that you then have to regain via propellant picked up at mars. Having any kind of braking necessary to reach your next propellant fill up, even if it is frictional braking is going to be really bad. But lets stop spit balling and crunch some numbers, lets say the destination is the Jovian system. Based on this table http://www.projectrho.com/public_html/rocket/appmissiontable.php I can deduce the mars to Jupiter deltaV.Direct from LEO we need 6.3 km/sIf we go to mars first we can depart with just 3.6 km/s to mars and if we capture fictionally all the way to LMO, then from LMO a burn of 4.3 km/s is needed to send you on to Jupiter. High mars orbit is 1.44 km/s above LMO so the Jupiter burn their would be 2.9 km/s from there.That's still a total of 7.9 km/s but it is admittedly broken up into two legs which are considerably less then the single burn from LEO. To convert that into propellant fraction at 380 ISP, at Earth you need 4.4:1 propellant to dry ratio to go to Jupiter, but to go to mars you need 1.6:1 and then at mars you need 2.1:1 to complete the journey.So total propellant is very similar with the direct from Earth method need 19 percent more total. The question is really one of the trades between availability of propellant at Earth and Mars, as I think propellant in mars orbit is going to be significantly more expensive then propellant in earth orbit so I think the direct approach wins.If you think 6.3 km/s is too much for one vehicle to handle then simply depart from a high Earth orbit which will split the deltaV very nicely into 3.2 and 3.1 which gets you virtually the same departure burn that you would have needed from high mars orbit, which proves my point their is no advantage to falling into the mars gravity well if your destination is an outer planet.But the whole idea is really moot anyway cause it would take lots more delta v then is viable upon arrival to just land on a moon like Callisto, Titan would be do able with aero-braking and direct decent but we are not going to send people out that far in any kind of conceivable time frame.
Is he talking about the asteroid belt or something, I can't see the landing vehicle with it's normal atmospheric EDL profile being appropriate on any other planetary body in the solar system other then Venus.
Land on Ceres or the Moon. Musk had earlier made reference to landing MCT on the Moon. Ceres would be similar.The landing thrust is not necessarily a big problem. You can do a burn above the surface and cut off thrust at just the right moment and fall the rest of the way, perhaps using RCS thrusters to finetune the landing.
The spacecraft formerly known as MCT could be purchased by some future billionaire or government space agency to land a large cargo payload on Titan's surface or just aerobrake at Titan and land on say, Enceladus.
Quote from: Robotbeat on 09/19/2016 03:10 pmLand on Ceres or the Moon. Musk had earlier made reference to landing MCT on the Moon. Ceres would be similar.The landing thrust is not necessarily a big problem. You can do a burn above the surface and cut off thrust at just the right moment and fall the rest of the way, perhaps using RCS thrusters to finetune the landing.Ceres? With chemical propulsion?The moon is certainly possible, though lunar ISRU (water ice) would clearly favor hydrolox (from what I remember).Quote from: philw1776 on 09/19/2016 11:24 amThe spacecraft formerly known as MCT could be purchased by some future billionaire or government space agency to land a large cargo payload on Titan's surface or just aerobrake at Titan and land on say, Enceladus.Sending cargo one-way doesn't require a vehicle like MCT. There's no need to land the entire Earth departure stage and the heat shield if they're not needed to get back. That said, an aeroshell of similar size is still required. For Venus colonization for example, I would expect payloads to go one way with expendable aeroshells.
The spacecraft formerly known as MCT could be purchased by some future billionaire or government space agency to land a large cargo payload on Titan's surface or just aerobrake at Titan and land on say, Enceladus. Various combinations thereof, possibly dropping off small landing vehicle payloads of several tons. Expensive but clearly matching the name of ITS. Would need a nuclear power source that far out but ITS should have the cargo hold space to fit one. Cut the nominal 100T cargo payload to some lower # to pick up delta V.
Quote from: Impaler on 09/17/2016 05:44 amIs he talking about the asteroid belt or something, I can't see the landing vehicle with it's normal atmospheric EDL profile being appropriate on any other planetary body in the solar system other then Venus. Venus it is then. It's the easiest place to colonize anyway.
The problem with Ceres is the extra delta V for out of plane xfer. However, slowing down @Ceres does not need delta V again for plane change. I have not run the #s myself to see what a cargo tonnes reduction offers in increased delta V in a Ceres scenario.
I am one that believes is unfairly overlooked to do to 'surfacism' and I find concepts like Landis2land and HAVOC plausible, deploying large balloons to float in the Venusian atmosphere at an altitude with a hospitable temperature and sunlight.