Heavy Lift Launch Vehicles VS Orbital Assembly

[Nibb31]

Fourth Option: A semi-permanent orbital construction platform - a smaller version of the ISS. Bring in the canisters, and allow the station crew to assemble as they arrive. This will probably be necessary for any sort of serious interplanetary exploration/colonization effort.

Way off the charts if we are considering current technology and costs. As I said, anything involving people doing the assembly work is going to be orders of magnitude more expensive than automated assembly.

[Robotengineer]

Fourth Option: A semi-permanent orbital construction platform - a smaller version of the ISS. Bring in the canisters, and allow the station crew to assemble as they arrive. This will probably be necessary for any sort of serious interplanetary exploration/colonization effort.

How would you be able to construct anything large enough to be useful on a station smaller than the ISS? If the station crew were the ones doing the building, you would need a rather large crew to be able to produce anything worth while, or if you had a small crew it would take them a lot longer to do it.

[sgt_flyer]

Orbital assembly using astronauts would be terribly exhausting for the crew if they have to put on EVA suits (even MCP suits) and not very efficient, because of the severely affected hand mobility. (Not counting the time spent donning the suits and prebreathing.)

You would need a pressurisable hangar for manual orbital assembly, so the astronauts could work in 'normal' work clothes. (So they'll have their full strength & dexterity at their disposal)

Now imagine having to use a lot of tools in a microgravity environment - they'll have to ensure safety at all points to prevent their work from damaging the hangar.

(Plus, arrays of anchor points / beams for the astronauts to grab on - imagine if an astronaut get into a space were he as nothing to grab on - besides, they'll need such supports if they ever need to have any meaningful leverage strength.

Edited October 7, 2015 by sgt_flyer

[Nibb31]

I'm picturing a large hab module, docking ports, and a crane attachment. Think of all the valuable work that was done using the space shuttle, and then imagine that you didn't need to carry anything into orbit. The 'platform' itself only needs to be big enough to house construction personnel, and hold itself to the ship/station being built.

Also, keep in mind that the crew wouldn't need to 'produce' anything, just fit the modules together and do wiring/internal assembly, and initial setup. Then we fly the mission crew up there, and they take it away. Funtionally, this would work like 'StarDock' in the Star Trek movies, but it would look more like a little ship moving around a big one and putting it together.

Star Trek science and engineering is based on magic. Not much of it makes any sense when you start thinking about the actual engineering problems and the best way to solve them.

We've already had this discussion. There is no need for a closed "dry dock" unless you have lots of workers doing manual work on the outside of the vehicle, which is something that you would avoid by design in the first place. Humans are the most expensive thing you can send to space. Most assembly work has to be automated. You might need an occasional EVA now and then, but it would be much more efficient to design your spacecraft to minimize orbital work rather than to design and build a massive space dock.

Edited October 7, 2015 by Nibb31

[Guest]

There is no need for a closed "dry dock" unless you have lots of workers doing manual work on the outside of the vehicle, which is something that you would avoid by design in the first place.

It's a good thing that's not what he described in his post.

[Robotengineer]

I'm picturing a large hab module, docking ports, and a crane attachment. Think of all the valuable work that was done using the space shuttle, and then imagine that you didn't need to carry anything into orbit. The 'platform' itself only needs to be big enough to house construction personnel, and hold itself to the ship/station being built.

Also, keep in mind that the crew wouldn't need to 'produce' anything, just fit the modules together and do wiring/internal assembly, and initial setup. Then we fly the mission crew up there, and they take it away. Funtionally, this would work like 'StarDock' in the Star Trek movies, but it would look more like a little ship moving around a big one and putting it together.

How many crew members would there be on the station? You would have to have sleeping quarters, dining area, exercise area and a place to store all of the food, water and life support mechanisms. If you had instead a crew of robonaut like robots, that would only need electricity and the occasional spare part, you could reduce the size of the station drastically.

[Kryten]

Well, that level of AI is pretty far off, IMO... But who knows

You don't need AI for uncrewed spacecraft maintenance, remote control from a ground station should work just fine. DEXTRE on the ISS has been operating this way for years.

[Nicholander]

I do see the problem, you need a lot of extra weight for rendezvous and docking the modules to the spacecraft. From what I see it, an unmanned tug which would bring the module to the station would be the best idea. But, how cheap would a tug cost? I think the cheapest way to do it would be to use the Progress as a baseline, take out the resupplies, replace it with RCS propellant, (It will need to be moving around a lot in orbit, and it won't be able to refuel often. (If at all.)) and put the front RCS thrusters on adjustable booms sticking out from the front, so it can dock with a large mass on it's front. (The module.)

And I also agree with what Rune said, that it's a best to use the biggest LV you can fly often. However, right now NASA doesn't have any HLLVs, let alone any that can be built cheaply, it seems that using the Atlas V (Or perhaps the Vulcan.) is the best choice. (And if you want to include private sector LVs, the Falcon 9.)

[Camacha]

Assembling ships in orbit is subject to the law of diminishing returns. The smaller the payloads are, the less efficient your operation and ship will be. If you need a bigger ship, you need a bigger launcher.

Besides, large launchers do not have to be complex.

[Generalstarwars333]

I would rather try to make a heavy lifter since I can't dock and stuff. haven't done that tutorial yet.

[fredinno]

I would rather try to make a heavy lifter since I can't dock and stuff. haven't done that tutorial yet.

The solution is simple. Use MechJeb.

[G'th]

I would rather try to make a heavy lifter since I can't dock and stuff. haven't done that tutorial yet.

Docking really isn't that bad. Nor is rendezvous even. If you can land on the Mun with any sort of precision, you can rendezvous and dock.

[fredinno]

Docking really isn't that bad. Nor is rendezvous even. If you can land on the Mun with any sort of precision' date=' you can rendezvous and dock.[/quote']

I suck at docking.

[Skyler4856]

Really depends on what you have to do. Designing a Rocket to lift 5x as much mass as the previous generation, might take a decade. Whereas using 6 launches, the extra launch to make up for the necessary docking equipment, will only take a couple of years

[Voyager55]

Why not use super-heavy LVs for orbital construction?

That's the plan. You aren't going to be able to launch a robust enough transfer vehicle in one 130 ton launch.

[Pipcard]

Between these two schools of thought:

"a mission with a few big pieces involves less mission complexity than one assembled in many small pieces"

"a launch vehicle that is only designed for heavy payloads would fly too rarely, resulting in expensive fixed costs"

(that is, unless you're trying to do something like mass colonization of Mars)

there is a compromise: modular booster stages. Think of Falcon 9 and Falcon Heavy, or (an upscaled version of) the Angara family. That way, the same manufacturing processes and launch facilities can be used for a super-heavy launcher or a medium launcher. A one-core launcher for comsats or crews to the space station, and several three or five-core launchers for manned missions to the Moon and Mars. Five cores would be a reasonable maximum for an expendable launcher, otherwise integration and operation of the launcher becomes too complex, or each modular core cannot handle all the extra loads during launch. Three cores is the reasonable maximum if you want to have SpaceX-style reusability operations.

Of course, there's also the issue of fairing size. Heavy payloads may not be able to fit in a small fairing, and the fairing can't be too wider than the stages, because you might get aerodynamic problems. So what I'm thinking of right now is a 5-m diameter launcher, capacity of about 20 tonnes to low Earth orbit, that scales up about 3 times with a 3-core version, which can have an 8-m fairing.

Edited November 6, 2015 by Pipcard

[fredinno]

Between these two schools of thought:

"a mission with a few big pieces involves less mission complexity than one assembled in many small pieces"

"a launch vehicle that is only designed for heavy payloads would fly too rarely, resulting in expensive fixed costs"

(that is, unless you're trying to do something like mass colonization of Mars)

there is a compromise: modular booster stages. Think of Falcon 9 and Falcon Heavy, or (an upscaled version of) the Angara family. That way, the same manufacturing processes and launch facilities can be used for a super-heavy launcher or a medium launcher. A one-core launcher for comsats or crews to the space station, and several three or five-core launchers for manned missions to the Moon and Mars. Five cores would be a reasonable maximum for an expendable launcher, otherwise integration and operation of the launcher becomes too complex, or each modular core cannot handle all the extra loads during launch. Three cores is the reasonable maximum if you want to have SpaceX-style reusability operations.

Of course, there's also the issue of fairing size. Heavy payloads may not be able to fit in a small fairing, and the fairing can't be too wider than the stages, because you might get aerodynamic problems. So what I'm thinking of right now is a 5-m diameter launcher, capacity of about 20 tonnes to low Earth orbit, that scales up about 3 times with a 3-core version, which can have an 8-m fairing.

But 5 cores would be assymetric. 6 is not, and it also happens to be the maximum number of cores you can put on a same diameter core as boosters.

"A one-core launcher for comsats or crews to the space station" That would be one large core-actually, that's basically what Falcon 9 V1.1 is. V.1.1 Full thrust is larger, so a Falcon Heavy Expendable isn't exactly what you envision as a 2-core version of the rocket, but somewhat smaller, say 38 T to LEO for a 2-core version of your LV rather than the 45 of Falcon Heavy. A 4-core version might carry 55 T to LEO, and a 6-core version 70T. Though, you probably want a larger 2nd stage on the 6-core version to take advantage of the extra thrust of the SRBs, so let's say 85T for the final evolution.

That wouldn't be too bad- it's smaller than the SLS workhorse Block IB, but you could probably send sizble chunks of a moon base with a launcher like that. That kind of solution probably would be less suited as a solution if NASA was deciding how to build the SLS, though, as SLS is basically Jupiter V4.0, which was designed to make use of existing tech and infrasturcture as much as possible.

Resuability is not a good idea for a SHLV, which won't exactly launch too often.

A multi-core rocket still has aerodynamic problems if you attach giant overhang fairings on it, though it does allow for larger fairings- Angara A5 has a 200% overhang fairing, rather than the 160% that's the usual maximum. Honestly, if I was desigining the rocket, I would make a 8-meter diameter (same as shuttle ET) RP-1 LOX stubby core, to allow for large fairing sizes on the larger versions. Yes, I recongize it would look weird, but NASA is considering 10 meter diameter fairings, as 8-meter fairings are too small for their human Mars landers- and these are for small (for humans) 15 T landers. To make a 30T lander, at least 10 meter would be required.

[Pipcard]

I meant 5 cores total, like Angara-A5.

And reusability would be for the single-core version (and for the three-core, Falcon Heavy style in which two cores return to the launch site and the center core is either expended or lands on a barge).

The issue is that 8 m is too wide for the 20-tonne LEO crew launcher/GTO comsat launcher.

Edited November 6, 2015 by Pipcard

[fredinno]

I meant 5 cores total, like Angara-A5.

And reusability would be for the single-core version (and for the three-core, Falcon Heavy style in which two cores return and the center core is either expended or lands on a barge).

The issue is that 8 m is too wide for the 20-tonne launcher.

A compromise 6.5 meters then?

I know a wider core is less aerodynamically efficient, but it also makes it easier to land for reusability.

[SciMan]

How about this:

Step 1. Build transit craft as large as desired in orbit, using smaller modules. (this part goes to and from orbit around the destination planet or moon)

Step 2a. Use the SLS-class launcher's superior payload fairing diameter to launch outsize cargo such as a lander or other things using heatshields on Mars.

Step 2b.Tugs launched with smaller rockets move the outsize cargo to the spacecraft under construction for docking.

Step 3. While being constructed, use the craft as a space station.

Step 4. Use the SLS-class launcher's superior payload mass capacity to launch a very large LH2/LOX transfer stage.

The basic idea here is to let each size rocket do what it's good at, and avoid sending up a payload on a too-big rocket at all costs (assuming that building a mid-size rocket or not launching the payload at all are not acceptable).

Orbital habitation stuff can be launched on smaller rockets, and as stated that removes the limit on max size of the craft.

This leaves the big rocket to do what it's built for, which is launching things too big and/or heavy for any other rocket. No sense sending up Sputnik on a Saturn-V.

Step 3 is important, and provides a fall-back plan should the big rocket have design or funding issues. Anything that can support a crew on its journey to Mars can support a research team in Earth orbit, and the same connections used to deliver the supplies while constructing the craft can be used to resupply the craft while in Earth orbit.

This isn't so much "take the ISS to mars" as it is "use the Mars Transit Vessel while in Earth Orbit".

Don't use super-low LEO either, there's too much air drag. I'd suggest an orbit somewhere from 1000-2500km altitude, as I don't think the Van Allen belts are THAT low.

As with most things, this isn't an "A" XOR "B" question. The best solution is somewhere in the middle.

[Generalstarwars333]

The solution is simple. Use MechJeb.

I tried to use mechjeb. my game lagged to about one frame every five weeks.

[Requia]

You end up needing both if you want to go anywhere manned farther than the Moon. No plan for Mars is actually less than 200t for habitat+transfer module, and making a huge number of launches is extraordinarily expensive, the ISS cost over 100 billion to assemble. And while people want to not include shuttle launch costs and instead say mid sized rockets are cheaper, we used exactly that any time it was an option. But those don't carry astronauts as well as loads, or have built in station keeping ability.

[fredinno]

I tried to use mechjeb. my game lagged to about one frame every five weeks.

reduce graphical quality settings in settings then.

[Generalstarwars333]

I think I've already done that to the max. plus with the amount of mods I just got it would kill my computer.