Rockets use a pulse thrust design to lift off from earth with roughly 10 to 15 minutes of durations..
To leave earth a simular push is done as well with the calculated distance to the destination being the determining factor for how long the pulse duration will be. Of course there is the mid and later duration correction pulses to make sure that we end up where we are desiring.
To get into orbit requires a reverse pulse of duration that is based on mass of the ship and the destinations gravitational forces. We can do a burn that uses the planets atmosphere to break the speed but its going to be followed at some point to stabilize the orbit. A slower speed to the destination that land it ahead of the destination would allow for a gravity capture as well.
Then there is the final burn to slow so that gravity can do its work to pull the ship towards the surface. Which depending on mass means no parachutes and lots of fuel to land the ship with retropropulsion.
To go home start at the initial step with the values being altered for the home destination....
For man the planning speed of transit and return are the factors that effect the mission surface duration. With the effects of that transit having functioning issues after return home that we do not have totally analyzed but that we do know what it does if we do nothing to counter it.
]]>If chemical rockets were the only game in town, the probes we've sent to visit multiple targets wouldn't be possible. The kind of propulsion I'm referring to is in-space propulsion, rather than launch from a significant gravity well. However, the efficiency of electric propulsion has a dramatic effect on the number of launches required to go from orbit to anywhere else that looks interesting.
]]>If you combine electric propulsion with artificial gravity, there's not a dime's worth of difference between getting to Mars in 6 months on loads of chemical propellant versus 6 months on inert gas or iodine. The only difference is how many propellant flights you have to send up and how much the overall solution costs as a function of all those propellant flights. BFS may be the right solution for sub-orbital / orbital transport, but the ultimate solution to interplanetary transport is still a real ITV that has the excess dV capability to contend with contingency scenarios.
BFR is not a rocket as it can go no where once in orbit and that is its problem...Lobing all the other rockets to refuel it before going is a boiloff or explosion with the LOX Methane waiting to happen until we have experience with them...
We would be better off sending up water, excess co2 and creating a fuel creation platform to refuel from. Solar panels on it to power the unit, batteries away from the fuel tanks, using the solar array to shade the fuel while its getting made, cryrogenation of Lox and liquid methane on orbit.
Park the ship, robotic connect the fuel hose connections and fill it up to go...No waiting on orbit for multiple ships and you can go when its time on each mars cycle.
We would be better off sending up water, excess co2 and creating a fuel creation platform to refuel from. Solar panels on it to power the unit, batteries away from the fuel tanks, using the solar array to shade the fuel while its getting made, cryrogenation of Lox and liquid methane on orbit.
Park the ship, robotic connect the fuel hose connections and fill it up to go...No waiting on orbit for multiple ships and you can go when its time on each mars cycle.
]]>Louis,
No argument about the maturity of SpaceX's rocket technology, but several rough field landings are still a requirement for going to Mars. Going to and from the moon would be a useful acid test / demonstration mission, too. All I want is a rigorous flight test program followed by an acid test to satisfy any lingering doubts about the maturity of the selected hardware. After that's done, Mars here we come. I also agree completely about the maturity of the tech to survive on Mars, although some of that can and should be tested on the moon first.
No argument about the maturity of SpaceX's rocket technology, but several rough field landings are still a requirement for going to Mars. Going to and from the moon would be a useful acid test / demonstration mission, too. All I want is a rigorous flight test program followed by an acid test to satisfy any lingering doubts about the maturity of the selected hardware. After that's done, Mars here we come. I also agree completely about the maturity of the tech to survive on Mars, although some of that can and should be tested on the moon first.
]]>Surviving on Mars is not a mature technology. The closest we have at the moment is ISS. I think there is so much work to be done in terms of water sourcing, ISRU, life support, propellant production, habitat construction, habitat environmental control, unloading the BFSs, communications with Earth, radiation protection, muscle and bone loss etc that it is mission critical, since it pretty much all has to be in place by 2022, only four years away (and some of it earlier in fact, to meet the cargo BFS launch of 2022 - you need to know what you're taking there).
The first time I see a successful outcome associated with the first item from that list, SpaceX can concern themselves with everything else required to actually live on Mars.
The first time I see a successful outcome associated with the first item from that list, SpaceX can concern themselves with everything else required to actually live on Mars.
[thumbs up]
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