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Saturn V flew about twice a year. I think it's easier today to get Falcon Heavy to fly 6 times a year, matching total payload, or to fly even more frequently. W

by avmich 7y ago

Saturn V flew about twice a year. I think it's easier today to get Falcon Heavy to fly 6 times a year, matching total payload, or to fly even more frequently. We have about 20 launches of Falcon 9, with 20+ tons payload each, which totals to 400+ tons annual - which is more than Saturn V carried per year.

ChuckMcM 7y ago
Yeah this. There are two things that work in our favor, one is that Falcon Heavy can (in theory) launch more quickly. And second, the mass needed to achieve a similar capability is greatly reduced due to materials technology. The only missing piece is that it would be nice to use cryogenic fuels but these outgas over time so long duration is not a thing. Solving the on-orbit refueling puzzle would make this sort of endeavor pretty straight forward from a planning standpoint.
btilly 7y ago
That requires orbital construction. Also that imposes very severe constraints on size and shape of those pieces. This is not technology that we have demonstrated in a meaningful way. For example the stage of the Apollo mission that took it from Earth orbit to a trajectory that would intercept the Moon was https://en.wikipedia.org/wiki/S-IVB https://en.wikipedia.org/wiki/S-IVB, which nearly twice the maximum payload of the Falcon Heavy. Do you really want to trust this step to a rocket that has to be assembled and fueled in space?
- nostrademons 7y ago
  Would you still need as heavy a lunar interceptor as the S-IVB? The Wikipedia page for it indicates that the S-IVB's engine was burned twice, once for the final push to achieve LEO and one for translunar injection. It was done this way so that the S-IB and S-V could share a common interface to the command & lunar modues for LEO flight tests. The Falcon Heavy goes straight to LEO; presumably you'd build a custom launch vehicle for TLI and landing and not need the portion of the S-IVB's propellant used to get to LEO.
- josho 7y ago
  > Do you really want to trust this step to a rocket that has to be assembled and fueled in space? Yes. Isn’t that the next logical step to developing space—the ability to build structures in orbit? That aside I wouldn’t object to building a Saturn V either.
  - sq_ 7y ago
    > Yes. Isn’t that the next logical step to developing space—the ability to build structures in orbit? I think you're totally right about this. If we want to really get going on living in space or even just doing certain manufacturing processes in space, it seems like we're going to need to start building real structures in orbit rather than fitting everything into a launch or two. My guess is that, if it doesn't happen now, we'll start doing construction in orbit if/when we start mining the Moon or asteroids. Not having to haul equipment up Earth's gravity well and producing fuel in situ seems like it will allow small launches on reusable "tugs" to become the most efficient means of getting things into space.
- GlenTheMachine 7y ago
  That's not for lack of trying by those of us in the space robotics community... There's a chicken and egg problem at work here. The robotics technology to do orbital construction exists, and in fact has existed for a couple of decades now. Nobody wants to fly it because the older technology - which amounts to “spend lots of money to fit your payload in a single rocket fairing” - has worked so far. The James Web Space Telescope will have a 6.5 meter primary optic. It will require something like 70 separate deployments in order to deploy the primary optic and the sunshield. At some point, custom designing hundreds of deployment mechanisms for every single mission becomes both more expensive and higher risk than just flying a damned robot arm. As does “just build a bigger rocket”. FYI, robotic refueling on orbit has been demonstrated a couple of times (Orbital Express and RRM).
- avmich 7y ago
  > That requires orbital construction. Do you know how many times two objects were successfully docked in space? And how many times they did that automatically? > Also that imposes very severe constraints on size and shape of those pieces. Objection to "very severe". You can have your standard fairing size full, with diameter about 5 meters and length of 15 meters or so. That's quite comparable to 6.6 meters diameter of Saturn-V payloads, is more than LEM without legs. What shape constraints you have in mind? > This is not technology that we have demonstrated in a meaningful way. We didn't demonstrate orbital docking technology? > nearly twice the maximum payload of the Falcon Heavy. But it was launched with one rocket altogether. Nobody prevents us from launching the booster stage separately and dock it with spacecraft on LEO. More, nobody prevents us from sending analog of Apollo spacecraft and LEM to the moon separately - with their own booster each. Those variants were considered in 1960-s and rejected purely on the basis of time to develop the technology - something which we have today well developed. > Do you really want to trust this step to a rocket that has to be assembled and fueled in space? Let me remind you that Gemini and Atlas-Agena stage docked and changed orbits in mid-1960-s, confirming that it at least can be done with then-current technology. Today ISS has a history of pushes by Shuttle, of refuels with Progress and ATV ships and I'm not sure what prevents using similar - though not identical - approach with translunar injections.
  - btilly 7y ago
    The component that I laid out is larger in both diameter and length than the standard fairing size you list. You are right that it would be possible to send the Apollo spacecraft and LEM to the Moon separately, to join there, but the Apollo spacecraft is 2/3 of that mass. The rocket to do the Apollo spacecraft by itself exceeds the specs that we can launch on Falcon Heavy. It would be more doable to build a multi-stage rocket in space and fire that. So one launch for Apollo+LEM, 2 launches for 2 booster stages. Put the three together and off you go. Of course this requires designing a new rocket, designed to be carried into space, to dock robotically, and then launch. Which is doable. But also isn't current tech. If we're going to build a new rocket ANYWAYS for this mission, I think it makes more sense to cross fingers and wait for SpaceX's SuperHeavy + Starship configuration. Update: While looking for current news on that, I found that SpaceX building SuperHeavy rockets in two locations. And I found that, today, they reported raising a billion dollars in funding for their development efforts. Which I submitted as a news article because I think that it is of interest separately from the NASA discussion.

by avmich 7y ago

ChuckMcM 7y ago

Yeah this. There are two things that work in our favor, one is that Falcon Heavy can (in theory) launch more quickly. And second, the mass needed to achieve a similar capability is greatly reduced due to materials technology. The only missing piece is that it would be nice to use cryogenic fuels but these outgas over time so long duration is not a thing. Solving the on-orbit refueling puzzle would make this sort of endeavor pretty straight forward from a planning standpoint.

btilly 7y ago

That requires orbital construction. Also that imposes very severe constraints on size and shape of those pieces. This is not technology that we have demonstrated in a meaningful way. For example the stage of the Apollo mission that took it from Earth orbit to a trajectory that would intercept the Moon was https://en.wikipedia.org/wiki/S-IVB https://en.wikipedia.org/wiki/S-IVB, which nearly twice the maximum payload of the Falcon Heavy. Do you really want to trust this step to a rocket that has to be assembled and fueled in space?

nostrademons 7y ago
Would you still need as heavy a lunar interceptor as the S-IVB? The Wikipedia page for it indicates that the S-IVB's engine was burned twice, once for the final push to achieve LEO and one for translunar injection. It was done this way so that the S-IB and S-V could share a common interface to the command & lunar modues for LEO flight tests. The Falcon Heavy goes straight to LEO; presumably you'd build a custom launch vehicle for TLI and landing and not need the portion of the S-IVB's propellant used to get to LEO.
josho 7y ago
> Do you really want to trust this step to a rocket that has to be assembled and fueled in space? Yes. Isn’t that the next logical step to developing space—the ability to build structures in orbit? That aside I wouldn’t object to building a Saturn V either.
- sq_ 7y ago
  > Yes. Isn’t that the next logical step to developing space—the ability to build structures in orbit? I think you're totally right about this. If we want to really get going on living in space or even just doing certain manufacturing processes in space, it seems like we're going to need to start building real structures in orbit rather than fitting everything into a launch or two. My guess is that, if it doesn't happen now, we'll start doing construction in orbit if/when we start mining the Moon or asteroids. Not having to haul equipment up Earth's gravity well and producing fuel in situ seems like it will allow small launches on reusable "tugs" to become the most efficient means of getting things into space.
GlenTheMachine 7y ago
That's not for lack of trying by those of us in the space robotics community... There's a chicken and egg problem at work here. The robotics technology to do orbital construction exists, and in fact has existed for a couple of decades now. Nobody wants to fly it because the older technology - which amounts to “spend lots of money to fit your payload in a single rocket fairing” - has worked so far. The James Web Space Telescope will have a 6.5 meter primary optic. It will require something like 70 separate deployments in order to deploy the primary optic and the sunshield. At some point, custom designing hundreds of deployment mechanisms for every single mission becomes both more expensive and higher risk than just flying a damned robot arm. As does “just build a bigger rocket”. FYI, robotic refueling on orbit has been demonstrated a couple of times (Orbital Express and RRM).
avmich 7y ago
> That requires orbital construction. Do you know how many times two objects were successfully docked in space? And how many times they did that automatically? > Also that imposes very severe constraints on size and shape of those pieces. Objection to "very severe". You can have your standard fairing size full, with diameter about 5 meters and length of 15 meters or so. That's quite comparable to 6.6 meters diameter of Saturn-V payloads, is more than LEM without legs. What shape constraints you have in mind? > This is not technology that we have demonstrated in a meaningful way. We didn't demonstrate orbital docking technology? > nearly twice the maximum payload of the Falcon Heavy. But it was launched with one rocket altogether. Nobody prevents us from launching the booster stage separately and dock it with spacecraft on LEO. More, nobody prevents us from sending analog of Apollo spacecraft and LEM to the moon separately - with their own booster each. Those variants were considered in 1960-s and rejected purely on the basis of time to develop the technology - something which we have today well developed. > Do you really want to trust this step to a rocket that has to be assembled and fueled in space? Let me remind you that Gemini and Atlas-Agena stage docked and changed orbits in mid-1960-s, confirming that it at least can be done with then-current technology. Today ISS has a history of pushes by Shuttle, of refuels with Progress and ATV ships and I'm not sure what prevents using similar - though not identical - approach with translunar injections.
- btilly 7y ago
  The component that I laid out is larger in both diameter and length than the standard fairing size you list. You are right that it would be possible to send the Apollo spacecraft and LEM to the Moon separately, to join there, but the Apollo spacecraft is 2/3 of that mass. The rocket to do the Apollo spacecraft by itself exceeds the specs that we can launch on Falcon Heavy. It would be more doable to build a multi-stage rocket in space and fire that. So one launch for Apollo+LEM, 2 launches for 2 booster stages. Put the three together and off you go. Of course this requires designing a new rocket, designed to be carried into space, to dock robotically, and then launch. Which is doable. But also isn't current tech. If we're going to build a new rocket ANYWAYS for this mission, I think it makes more sense to cross fingers and wait for SpaceX's SuperHeavy + Starship configuration. Update: While looking for current news on that, I found that SpaceX building SuperHeavy rockets in two locations. And I found that, today, they reported raising a billion dollars in funding for their development efforts. Which I submitted as a news article because I think that it is of interest separately from the NASA discussion.