5 ms·

I can't believe that I'm understanding this correctly? Just to be sure: NASA's plan is to fly the insanely expensive hasn't even launched into space yet SLS, on

I can't believe that I'm understanding this correctly? Just to be sure: NASA's plan is to fly the insanely expensive hasn't even launched into space yet SLS, onto some non-existing docking station, then SpaceX fly to the moon. Repeat back (does Starship have to dock again why can't it just go straight back into earth)? While Starship can go to from earth to moon with a refueling stop alone? Even if sticking to the space dock why not the WAYYYY cheaper Dragon which just worked today (using a recycled rocket)?

syoc 6y ago
I am way out of my comfort zone discussing this, but I really like the idea of building oribiting infrastructure. Not sure why they are not using an earth-moon Lagrange point. I agree that it would probably be cheaper and more practical to go directly to the moon with a simpler refuling scheme. I do however also believe that some infrastructure is needed for further space travel and a larger more permanent off-earth presence. Starting new missions from outside a strong gravity field seems like such a huge advantage. I guess most people want a destination and not just a more long term established presence.
- sneak 6y ago
  I imagine that we'd need hundreds or thousands of people in space to make such a base/fuel depot worth it - IIRC it's less fuel to use a transfer orbit than to go to L4 or L1 and stop on the way. Such a thing might make sense once there are, say, 50 or 100 starships. For the foreseeable future, all missions will "start" in Earth's gravity well due to the fact that the o2 and ch4 are all down here. It will be some years until we have significant fuel stores in space.
- Armisael16 6y ago
  > Starting new missions from outside a strong gravity field seems like such a huge advantage. You don’t get to do this, period. All your crew and all your materials are ultimately coming from Earth (or, in some plans, are mined in-situ). You use considerably more resources getting to your waypoint than you save by leaving from there. Being farther out of the gravity well isn’t entirely positive either; you’re losing out on significant savings from the Oberth effect. Earth-Moon Lagrange points are well past the minimum-cost orbit.
  - avmich 6y ago
    > All your crew and all your materials are ultimately coming from Earth Wait till we start making LOX (and later, I think, metals) on the Moon from regolith. The process is old and tested on Earth, the missing part is actually experimenting with this on the Moon. And as soon as we have more or less robust Earth-Moon transportation, this will become important, as it will significantly simplify near Moon operations. Do you know NASA runs, right now, competitions for e.g. lunar ice extraction and purifying?
  - ethbr0 6y ago
    > All your crew and all your materials are ultimately coming from Earth This is the key state differentiator. If you bring everything from Earth, it doesn't make sense. (So why are we doing it now?) But once you start procuring resources from outside gravity well, things look different.
    - Yizahi 6y ago
      Exactly what do you plan to acquire/create outside of Earth, and from where to where do you plan to transfer it realistically? Except for fully autonomous human colonies which will mine stuff nearby and use, almost no transfer of resources in space makes sense, it is way too costly and there is no demand (even imaginary). Since there is no need for that, there is also no need for transfer stations (warehouses) anywhere, be it a planet orbit or Lagrange points.
      - m4rtink 6y ago
        Propelant depots, those make all the difference.
        zardo 6y ago
        They make sense for an individual mission. Bring up fuel and leave it in the parking orbit. But the optimal parking orbits are going to be different for different destinations, vehicles, and times.
    - 6y ago
- Yizahi 6y ago
  Only some orbits would intersect with L1 point, others will require immense fuel waste to get there and then change orbit to original target. Also there are no gas stations in space, for multiple reasons - there is no steady demand to fuel in space, it is at best sporadic and spiky, and in the mean time you'll need to keep up cryo fuel from boiling off; then it is hard to operate anything remotely, so Gateway gas station would be harder to operate than ISS in LEO; there is no need to place gas station farther than LEO because in space we don't need to bother with actual distances, but with gravity. Earth to Mars is 62 million kilometers, so speaking in analogies it would make sense to refuel at half of the distance, similar to the traveling by car from New York to San Francisco. But in reality it is not. Getting 300 kilometers from Earth to LEO takes 9 km/s of delta V, getting the rest 62000000 kilometers from LEO to Mars takes 5-6 km/s of delta V. LEO is much more than half way to Mars already and there is literally zero point is refuelling anywhere else (excluding fuel generation in space possibility).
avmich 6y ago
> does Starship have to dock again why can't it just go straight back into earth Because Moon-bound Starship will be quite different from Earth-bound - not enough to not call it Starship, but still - the Moon-bound will be optimized for less gravity (different legs?), no atmosphere (no wings), braking using engines in the middle of the body, not in the tail section, Moon-specific systems like ladder or elevator etc.
- m4rtink 6y ago
  AFAIK lunar Starship still has Raptors in the tail that do most of the burns, the "belt" engines are only used for the final landing phase to reduce the ammount of regolith kicked up by the rocket plumes contact with the surface.
- dillondoyle 6y ago
  Interesting. So would still do a 'dock' and could come back on a different Starship, Dragon, or SLS it sounds like
kimundi 6y ago
Separating the "get to/from moon" vehicle from the "land on/start from moon) vehicle has indeed been the plan for many years now.
lutorm 6y ago
hasn't even launched into space yet SLS I'm no fan of SLS, but check your terminology here: You're talking about Starship in the present tense, but it hasn't launched _either_, so you can't say it "can" go to the moon etc either. Starship is awesome, but it's an insanely ambitious project. No one knows how long it'll take to get it right.
- avmich 6y ago
  Raptor engines are, yes, cutting edge. Serious stuff. Starship itself?.. Being built with such technologies, so cheap (Elon mentioned that Boca Chica works are quite small percents of what SpaceX is doing in terms of money), so fast - and yet we already have a successful-ish landing from ~10 km height. Of course, we don't know for sure. But it surely doesn't seem too bad, especially now - and for some it was clear when SpaceX was just created.
- m4rtink 6y ago
  Well, Starship has definitely reached bigger height than SLS so far (unless you count some of the reused Shuttle engines). ;-) Also considering the planned SLS "landing" mode they are also on par so far.
- dillondoyle 6y ago
  That's totally 100% fair critique. But SLS is in no way able to go to moon or earth with what they are currently building? What makes this so weird to me is that SpaceX does have Dragon already which just brought more people into orbit this week - e.g. proven and way cheaper of what SLS is supposed to do in this mission - unless I'm missing or not understanding something. So you're right the starship portion to moon (and hopefully mars) is similar to SLS in that it's not realized ye But looking at the part SLS is supposed to play in this production, that role has already been acted successfully by Dragon. I'd say spacex gets the space oscar for it, though i doubt they get the trophy this weekend :)
  - wmf 6y ago
    Orion does have several spec advantages over Crew Dragon such as larger volume and longer endurance. https://www.quora.com/What-are-the-key-differences-between-the-SpaceX-Dragon-Lockheed-Orion-and-Boeing-CST-100-spacecrafts https://www.quora.com/What-are-the-key-differences-between-t... Given SpaceX's dramatically faster and cheaper development, it might be possible to deliver an upgraded Crew Dragon Plus (or whatever you want to call it) before Orion is ready.

syoc 6y ago

I am way out of my comfort zone discussing this, but I really like the idea of building oribiting infrastructure. Not sure why they are not using an earth-moon Lagrange point. I agree that it would probably be cheaper and more practical to go directly to the moon with a simpler refuling scheme. I do however also believe that some infrastructure is needed for further space travel and a larger more permanent off-earth presence. Starting new missions from outside a strong gravity field seems like such a huge advantage. I guess most people want a destination and not just a more long term established presence.

sneak 6y ago
I imagine that we'd need hundreds or thousands of people in space to make such a base/fuel depot worth it - IIRC it's less fuel to use a transfer orbit than to go to L4 or L1 and stop on the way. Such a thing might make sense once there are, say, 50 or 100 starships. For the foreseeable future, all missions will "start" in Earth's gravity well due to the fact that the o2 and ch4 are all down here. It will be some years until we have significant fuel stores in space.
Armisael16 6y ago
> Starting new missions from outside a strong gravity field seems like such a huge advantage. You don’t get to do this, period. All your crew and all your materials are ultimately coming from Earth (or, in some plans, are mined in-situ). You use considerably more resources getting to your waypoint than you save by leaving from there. Being farther out of the gravity well isn’t entirely positive either; you’re losing out on significant savings from the Oberth effect. Earth-Moon Lagrange points are well past the minimum-cost orbit.
- avmich 6y ago
  > All your crew and all your materials are ultimately coming from Earth Wait till we start making LOX (and later, I think, metals) on the Moon from regolith. The process is old and tested on Earth, the missing part is actually experimenting with this on the Moon. And as soon as we have more or less robust Earth-Moon transportation, this will become important, as it will significantly simplify near Moon operations. Do you know NASA runs, right now, competitions for e.g. lunar ice extraction and purifying?
- ethbr0 6y ago
  > All your crew and all your materials are ultimately coming from Earth This is the key state differentiator. If you bring everything from Earth, it doesn't make sense. (So why are we doing it now?) But once you start procuring resources from outside gravity well, things look different.
  - Yizahi 6y ago
    Exactly what do you plan to acquire/create outside of Earth, and from where to where do you plan to transfer it realistically? Except for fully autonomous human colonies which will mine stuff nearby and use, almost no transfer of resources in space makes sense, it is way too costly and there is no demand (even imaginary). Since there is no need for that, there is also no need for transfer stations (warehouses) anywhere, be it a planet orbit or Lagrange points.
    - m4rtink 6y ago
      Propelant depots, those make all the difference.
      - zardo 6y ago
        They make sense for an individual mission. Bring up fuel and leave it in the parking orbit. But the optimal parking orbits are going to be different for different destinations, vehicles, and times.
  - 6y ago
Yizahi 6y ago
Only some orbits would intersect with L1 point, others will require immense fuel waste to get there and then change orbit to original target. Also there are no gas stations in space, for multiple reasons - there is no steady demand to fuel in space, it is at best sporadic and spiky, and in the mean time you'll need to keep up cryo fuel from boiling off; then it is hard to operate anything remotely, so Gateway gas station would be harder to operate than ISS in LEO; there is no need to place gas station farther than LEO because in space we don't need to bother with actual distances, but with gravity. Earth to Mars is 62 million kilometers, so speaking in analogies it would make sense to refuel at half of the distance, similar to the traveling by car from New York to San Francisco. But in reality it is not. Getting 300 kilometers from Earth to LEO takes 9 km/s of delta V, getting the rest 62000000 kilometers from LEO to Mars takes 5-6 km/s of delta V. LEO is much more than half way to Mars already and there is literally zero point is refuelling anywhere else (excluding fuel generation in space possibility).

avmich 6y ago

> does Starship have to dock again why can't it just go straight back into earth Because Moon-bound Starship will be quite different from Earth-bound - not enough to not call it Starship, but still - the Moon-bound will be optimized for less gravity (different legs?), no atmosphere (no wings), braking using engines in the middle of the body, not in the tail section, Moon-specific systems like ladder or elevator etc.

m4rtink 6y ago
AFAIK lunar Starship still has Raptors in the tail that do most of the burns, the "belt" engines are only used for the final landing phase to reduce the ammount of regolith kicked up by the rocket plumes contact with the surface.
dillondoyle 6y ago
Interesting. So would still do a 'dock' and could come back on a different Starship, Dragon, or SLS it sounds like

kimundi 6y ago

Separating the "get to/from moon" vehicle from the "land on/start from moon) vehicle has indeed been the plan for many years now.

lutorm 6y ago

hasn't even launched into space yet SLS I'm no fan of SLS, but check your terminology here: You're talking about Starship in the present tense, but it hasn't launched _either_, so you can't say it "can" go to the moon etc either. Starship is awesome, but it's an insanely ambitious project. No one knows how long it'll take to get it right.

avmich 6y ago
Raptor engines are, yes, cutting edge. Serious stuff. Starship itself?.. Being built with such technologies, so cheap (Elon mentioned that Boca Chica works are quite small percents of what SpaceX is doing in terms of money), so fast - and yet we already have a successful-ish landing from ~10 km height. Of course, we don't know for sure. But it surely doesn't seem too bad, especially now - and for some it was clear when SpaceX was just created.
m4rtink 6y ago
Well, Starship has definitely reached bigger height than SLS so far (unless you count some of the reused Shuttle engines). ;-) Also considering the planned SLS "landing" mode they are also on par so far.
dillondoyle 6y ago
That's totally 100% fair critique. But SLS is in no way able to go to moon or earth with what they are currently building? What makes this so weird to me is that SpaceX does have Dragon already which just brought more people into orbit this week - e.g. proven and way cheaper of what SLS is supposed to do in this mission - unless I'm missing or not understanding something. So you're right the starship portion to moon (and hopefully mars) is similar to SLS in that it's not realized ye But looking at the part SLS is supposed to play in this production, that role has already been acted successfully by Dragon. I'd say spacex gets the space oscar for it, though i doubt they get the trophy this weekend :)
- wmf 6y ago
  Orion does have several spec advantages over Crew Dragon such as larger volume and longer endurance. https://www.quora.com/What-are-the-key-differences-between-the-SpaceX-Dragon-Lockheed-Orion-and-Boeing-CST-100-spacecrafts https://www.quora.com/What-are-the-key-differences-between-t... Given SpaceX's dramatically faster and cheaper development, it might be possible to deliver an upgraded Crew Dragon Plus (or whatever you want to call it) before Orion is ready.