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> The shortest time between resupply missions to Mars is two years. You aren't going to be sending only one ship at a time. You will be staggering shipments, w

> The shortest time between resupply missions to Mars is two years. You aren't going to be sending only one ship at a time. You will be staggering shipments, with 3-4 ships in transit at a time. You could make the time between resupplies as short as you want.

jfoutz 8y ago
Resupply isn’t quite the right word. If I break the X, i have to fix it myself or wait 2 years.
lisper 8y ago
You don't understand the orbital mechanics of getting to Mars. Getting to Mars only takes eight months, but you have to launch when Earth and Mars are in a particular configuration relative to each other, and that configuration only happens every two (Earth) years. You can launch as many ships as you like during those windows, but you can't stagger them.
- craftyguy 8y ago
  Only if you want them to take no more than 18 months to arrive.. You can most definitely stagger supply ships and launch them at any time, it's just that some will take a bit longer than others to arrive and their various transit times can be taken into account to have them arrive in a staggered fashion.
  - lisper 8y ago
    Well, sure, but how does that help? It's no different than having them arrive all at once and just waiting to open them. Whether they sit around on Mars or sit around in space doesn't matter.
    - craftyguy 8y ago
      > Well, sure, but how does that help? It enables a continuous supply, without having to try to plan everything to happen all at once during a short launch window/timeframe > You can launch as many ships as you like during those windows, but you can't stagger them. Well, you don't have to only launch "during those windows". I'm no logistic genius, but it seems like it would be easier/more cost effective to loft resources towards Mars at intervals that don't depend on a relatively short event that occurs every ~18 months. Try collecting all of the things you need to go camping 30 minutes beforehand, vs over the period of a week/month before you go. Yea, not very effective.. ? Your comment I replied to above seems to be overly aggressive (that doesn't belong here): > You don't understand the orbital mechanics of getting to Mars. I'm quite sure there are lots of things you (or I) don't understand. Try being more constructive next time.
      - lisper 8y ago
        > It enables a continuous supply No, it doesn't, as I explained in the GP comment. > I'm no logistic genius Yes, that's pretty clear. > Try being more constructive next time. Try being a little more appreciative when someone offers you their expertise for free [1]. And consider the possibility that /u/kakarot doesn't need you to be their white knight. Just FYI, I used to be a Principal Scientist at NASA where I worked on, among other things, the R&D program that led up to the Mars Pathfinder mission. So while I never designed orbital trajectories myself, I spent years hanging out with the people who did it for a living. Yes, there are a lot of things I don't understand, but the fundamental difficulties of shipping stuff to Mars are not among them. --- [1] OK, it's not quite free. The price is putting up with the fact that I'm a curmudgeon. Some people think that's a fair deal. If you don't, well, no one is putting a gun to your head and forcing you to engage with me.
- kakarot 8y ago
  I do understand the orbital mechanics of getting to Mars. It's the same as the orbital mechanics of getting to anywhere. I assume you're talking about the Hohmann transfer [0], which is the most efficient path a ship could take. We're not optimizing for efficiency here, we're optimizing for delivery. You should also realize that while there is a specific moment of peak efficiency in launch times, you have a window on the order of months before a Hohmann transfer becomes less efficient than other methods. Once every 2 years sounds less drastic when it's 6 months out of those 2 years. All that being said, the Hohmann transfer is a lot sketchier in practice than one would think. Neither Mars nor Earth has a perfectly circular orbit. It's often easier just to take the old-fashioned route. Take a look at this chart [1] for an idea of the spread of trip length vs launch time. [0] http://www.planetary.org/multimedia/space-images/charts/hohmann-transfer-orbit.html http://www.planetary.org/multimedia/space-images/charts/hohm... [1] https://mars.jpl.nasa.gov/spotlight/images/porkchop_lg.gif https://mars.jpl.nasa.gov/spotlight/images/porkchop_lg.gif
  - lisper 8y ago
    > I do understand the orbital mechanics of getting to Mars. It's the same as the orbital mechanics of getting to anywhere. Then you don't understand the economics. Or maybe it's something else you don't understand, but you are clearly missing something. The orbital mechanics of getting to any target in the solar system are unique to that target. Designing orbital trajectories is a profession unto itself. Yes, it is theoretically possible to have staggered deliveries so that spacecraft arrive at Mars on a schedule other than every two years. But think about it: how would this help? The schedule on which the supply craft arrive doesn't matter. What matters is the latency between when a need manifests itself and when it can be fulfilled. Fundamental physics lets you get to Mars in a matter of days if you could accelerate and decelerate the entire time at 1-G. But you can't, not because orbital mechanics forbids it, but because technology and economics and the rocket equation forbids it. The one thing you're going to need to optimize for more than anything else is kilogram delivered per dollar spent. That means being as efficient as you possibly can because launch costs are ridiculously high even with reusable boosters. That means using Hohmann orbits, and that means eight month transfer times with launch windows every two years. Yes, those windows are fairly broad, but that doesn't matter. You're still going to have to wait for periods of time measured in months and years for your Amazon order to be fulfilled on Mars.

jfoutz 8y ago

Resupply isn’t quite the right word. If I break the X, i have to fix it myself or wait 2 years.

lisper 8y ago

You don't understand the orbital mechanics of getting to Mars. Getting to Mars only takes eight months, but you have to launch when Earth and Mars are in a particular configuration relative to each other, and that configuration only happens every two (Earth) years. You can launch as many ships as you like during those windows, but you can't stagger them.

craftyguy 8y ago
Only if you want them to take no more than 18 months to arrive.. You can most definitely stagger supply ships and launch them at any time, it's just that some will take a bit longer than others to arrive and their various transit times can be taken into account to have them arrive in a staggered fashion.
- lisper 8y ago
  Well, sure, but how does that help? It's no different than having them arrive all at once and just waiting to open them. Whether they sit around on Mars or sit around in space doesn't matter.
  - craftyguy 8y ago
    > Well, sure, but how does that help? It enables a continuous supply, without having to try to plan everything to happen all at once during a short launch window/timeframe > You can launch as many ships as you like during those windows, but you can't stagger them. Well, you don't have to only launch "during those windows". I'm no logistic genius, but it seems like it would be easier/more cost effective to loft resources towards Mars at intervals that don't depend on a relatively short event that occurs every ~18 months. Try collecting all of the things you need to go camping 30 minutes beforehand, vs over the period of a week/month before you go. Yea, not very effective.. ? Your comment I replied to above seems to be overly aggressive (that doesn't belong here): > You don't understand the orbital mechanics of getting to Mars. I'm quite sure there are lots of things you (or I) don't understand. Try being more constructive next time.
    - lisper 8y ago
      > It enables a continuous supply No, it doesn't, as I explained in the GP comment. > I'm no logistic genius Yes, that's pretty clear. > Try being more constructive next time. Try being a little more appreciative when someone offers you their expertise for free [1]. And consider the possibility that /u/kakarot doesn't need you to be their white knight. Just FYI, I used to be a Principal Scientist at NASA where I worked on, among other things, the R&D program that led up to the Mars Pathfinder mission. So while I never designed orbital trajectories myself, I spent years hanging out with the people who did it for a living. Yes, there are a lot of things I don't understand, but the fundamental difficulties of shipping stuff to Mars are not among them. --- [1] OK, it's not quite free. The price is putting up with the fact that I'm a curmudgeon. Some people think that's a fair deal. If you don't, well, no one is putting a gun to your head and forcing you to engage with me.
kakarot 8y ago
I do understand the orbital mechanics of getting to Mars. It's the same as the orbital mechanics of getting to anywhere. I assume you're talking about the Hohmann transfer [0], which is the most efficient path a ship could take. We're not optimizing for efficiency here, we're optimizing for delivery. You should also realize that while there is a specific moment of peak efficiency in launch times, you have a window on the order of months before a Hohmann transfer becomes less efficient than other methods. Once every 2 years sounds less drastic when it's 6 months out of those 2 years. All that being said, the Hohmann transfer is a lot sketchier in practice than one would think. Neither Mars nor Earth has a perfectly circular orbit. It's often easier just to take the old-fashioned route. Take a look at this chart [1] for an idea of the spread of trip length vs launch time. [0] http://www.planetary.org/multimedia/space-images/charts/hohmann-transfer-orbit.html http://www.planetary.org/multimedia/space-images/charts/hohm... [1] https://mars.jpl.nasa.gov/spotlight/images/porkchop_lg.gif https://mars.jpl.nasa.gov/spotlight/images/porkchop_lg.gif
- lisper 8y ago
  > I do understand the orbital mechanics of getting to Mars. It's the same as the orbital mechanics of getting to anywhere. Then you don't understand the economics. Or maybe it's something else you don't understand, but you are clearly missing something. The orbital mechanics of getting to any target in the solar system are unique to that target. Designing orbital trajectories is a profession unto itself. Yes, it is theoretically possible to have staggered deliveries so that spacecraft arrive at Mars on a schedule other than every two years. But think about it: how would this help? The schedule on which the supply craft arrive doesn't matter. What matters is the latency between when a need manifests itself and when it can be fulfilled. Fundamental physics lets you get to Mars in a matter of days if you could accelerate and decelerate the entire time at 1-G. But you can't, not because orbital mechanics forbids it, but because technology and economics and the rocket equation forbids it. The one thing you're going to need to optimize for more than anything else is kilogram delivered per dollar spent. That means being as efficient as you possibly can because launch costs are ridiculously high even with reusable boosters. That means using Hohmann orbits, and that means eight month transfer times with launch windows every two years. Yes, those windows are fairly broad, but that doesn't matter. You're still going to have to wait for periods of time measured in months and years for your Amazon order to be fulfilled on Mars.