Author Topic: Space Truck: Space Station Construction Requirements - Speculation  (Read 5573 times)

Offline Norm38

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The Space Shuttle built ISS, with American modules that were for the most part designed to fit the existing dimensions of the cargo bay.  With Shuttle retired, the next orbital station will be built by something else. Possibly an ITS derivative. We don't need to focus on ITS exclusively, but it's a useful starting point for the discussion.

Maybe a dedicated thread is overkill, but I wanted to start a discussion on cargo bay dimensions, the size and functionality of modules that allows, and how that impacts other vehicle parameters such as overall diameter.

Is it best to stick with ISS type dimensions?  Or something more square (squat)? If you are designing a new space station, fuel depot, etc (not just Bigalow modules), what are your cargo bay requirements? What does a space truck have to look like to get the job done?

Dimensions
Shuttle Bay:       18 x 4.6m dia.     300m3
Zvezda:             13.1 x 4.1m dia.  173m3
Kibo:                 11.2 x 4.6m dia.  186m3
Bigalow "990"     20 x 10m dia.      1570m3  -  Not going to fit ITSy

ITSy Option:     10m x 7m dia.     385m3


Image credit to lamontagne
« Last Edit: 08/29/2017 07:23 PM by Norm38 »

Offline RonM

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It's not going to be design the cargo bay for the space station modules, it's going to be what can we fit in the cargo bay of the space truck.

What do you mean by more square?

Offline Lar

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The shuttle payload bay is long and narrow. ITSy's cargo area is squatter (more square). That's my guess.
"I think it would be great to be born on Earth and to die on Mars. Just hopefully not at the point of impact." -Elon Musk
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Offline DOCinCT

Not all modules were launched via Shuttle.  The largest module , Zvezda, was a Proton M and measured 43ft x 13.5ft.  The longest Shuttle module was Kibo at 36.7ft and the largest diameter, Leonardo, was 15 ft.

Offline Norm38

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Could Shuttle have carried Zvezda? It fits.
Maybe FH is used to launch big self propelled modules, I'm curious about the cargo bay.

Looks like the ITSy bay could be 15m long but 7-8m in diameter. ~600m3.  But could be only 10m x 7m, 385m3.

Shuttle was 300m3, Kibo 186m3.  Roughly.

Offline Space Ghost 1962

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Shuttle payloads also were designed to be trunnion mounted for the Shuttle to accept loads through load paths via the sides of the cargo bay vertically, as well as cases where return loads could be accepted horizontally through spars.

It is unclear the facility of a BFS/ITS/ITSy payload bay. Suffice to say that fat/wide payloads aren't currently very desirable, especially with a sole platform to fly them.

And no, Shuttle likely would not have been able to fly Zvezda for various reasons. First, it was designed to be launched by Proton. Yes it could have been modified, but to no advantage.

You have existing FH/F9/EELV/other payloads. Apart from SX unique needs, the "paying" payloads will "look" like the existing ones. With few exceptions.

This will only change when multiple vehicles start flying with superset sizes/capacities/capabilities. And then the lag times will be 4-5 years after flight proven. Because that's how long it will take to factor them in.

Offline M_Puckett

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The Space Shuttle built the ISS the way it did because we did not have a Saturn V class launcher to launch Skylab or bigger class modules.

It was a thing of necessity, not a thing of optimization.

If you have a 9M ITS, Launch 8M modules under a 9M faring, not in a cargo bay.

Or launch something Bigelow that inflates to 15M.

Offline Roy_H

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I envision a rotating space station with a non-rotating core for spaceship docking, manufacturing and experimenting in a weightless environment. The living area would be in the outer ring which would rotate at 1 or 2 rpm and consist of Bigelow 990 modules strung end to end in a circle. For 2 rpm this would be about 36 modules. Of course there is no such thing as a Bigelow 990, but my proposal would use this size about 10m dia and 18 to 20m long. This size works well to allow a central sidewalk size walkway to run continuously through all the modules, with each module having an upstairs living quarters and a "basement" below for utilities, water, electrical service etc. The main floor would have common living areas and offices. Agricultural modules would not have the upper living level.

So, to get back to the question in this thread, I think this style module would have to be pre-fabricated on earth and sent up with floors and rooms installed so that means pre-inflated. Cargo bay would therefore have to be slightly larger than 10m dia and 20m long.
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Offline Coastal Ron

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You have existing FH/F9/EELV/other payloads. Apart from SX unique needs, the "paying" payloads will "look" like the existing ones. With few exceptions.

This will only change when multiple vehicles start flying with superset sizes/capacities/capabilities. And then the lag times will be 4-5 years after flight proven. Because that's how long it will take to factor them in.

A good point, and one that I've echoed in the past.

We need to focus more on what can be done with commodity transportation, because historically it has been the cost of doing things in space that has been the greatest barrier, not technology. And I think our experience with the ISS has shown that we have not yet reached the maximum size potential of structures that are assembled from components that can fit on the current worldwide fleet of commercial launchers.

For Ariane 5 and Falcon 9/H they can carry payloads up to 4.5m in diameter within their fairings, and at least 6.7m in length, but to make sure more international launchers can be used it would be better to assume a slightly small diameter (JAXA H-IIB is likely 4.4M diameter capable).

And while the least expensive option would be to standardize on the least expensive launch provider(s), I would advocate that it would be better overall to involve as many nations as possible and anticipate that some launches would be done by higher cost providers. In other words spread the launch participation as much as possible, and by getting more companies, individuals and nations involved the in-space costs will likely be lower over the long run.

Then, as capabilities average up in size, the average payload size can be increased. So this approach is not limiting, but ensures the highest level of participation from the beginning.

My $0.02
If we don't continuously lower the cost to access space, how are we ever going to afford to expand humanity out into space?

Online SweetWater

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Is it best to stick with ISS type dimensions?  Or something more square (squat)? If you are designing a new space station, fuel depot, etc (not just Bigalow modules), what are your cargo bay requirements? What does a space truck have to look like to get the job done?

I think it probably depends on what the purpose of the station is. A fuel depot is going to look very different from a station that caters to space tourists, and a station designed for microgravity science is going to look very different from one with other science objectives.

Also, it is worth remembering that many of the Russian components for the ISS performed autonomous rendezvous and docking with the station. There is no reason to assume that the ITS will assume a shuttle-like role in delivering modules to a future station. I think it is far more likely that a re-usable first stage (the ITS booster, New Glenn, etc.) will boost modules to orbit, and they will rendezvous with the station themselves and then either perform autonomous docking or a robot arm on the station will conduct berthing operations.

Offline Norm38

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If you have a 9M ITS, Launch 8M modules under a 9M faring, not in a cargo bay.

How many different versions will they build?  If the portion of the ship that contains the cargo bay is essential for re-entry, then it can't simply shed fairings.  And the whole point of full reuse is to not drop fairings. If a 5m fairing costs $6mil, then 9m is at least $20mil.  A lot to throw away per mission.

Offline Norm38

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I think it is far more likely that a re-usable first stage (the ITS booster, New Glenn, etc.) will boost modules to orbit, and they will rendezvous with the station themselves and then either perform autonomous docking or a robot arm on the station will conduct berthing operations.

Any LEO station module that has to include propulsion can always fly itself into position, not an issue.  But does every module need propulsion?  Could ISS have been assembled from something like Cygnus modules?  Does the propulsion portion stay attached forever, or does it detatch and reenter?  What about things like the solar arrays and trusses?  Are they all self-propelled?
Fuel, engines, attitude control, navigation, power.  A lot of extra hardware, mass and cost, per module.

I am looking at this from a commodity aspect.  Assume SpaceX is flying the 9m ITSy at the rates they want to fly it. Assume its the lowest cost option. Does it make sense to launch smaller self-propelled modules on more expensive rockets, or to launch larger more capable modules on ITSy?  If so, what will engineers do with that capability?
« Last Edit: 08/29/2017 02:32 PM by Norm38 »

Offline Lar

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If you want to minimize cost but feel you need propulsion on all modules, it probably ought to be modular so that it can be detached from modules as they are emplaced, and either reattached in a central place to be used for stationkeeping (after being refueled) or put in a cargo bay and returned to earth.
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Offline guckyfan

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If you want to minimize cost but feel you need propulsion on all modules, it probably ought to be modular so that it can be detached from modules as they are emplaced, and either reattached in a central place to be used for stationkeeping (after being refueled) or put in a cargo bay and returned to earth.

Or use them as tugs to place more modules.

Offline Coastal Ron

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Any LEO station module that has to include propulsion can always fly itself into position, not an issue.  But does every module need propulsion?

No. If we use the terrestrial analogy of how we move cargo around today, we would use some form of reusable tug to grab the cargo out of the delivery vehicle and either store it for later or move it to the construction site. Different analogies would be either a tug/tractor (for longer distances) or a forklift (for short distances).

Quote
Could ISS have been assembled from something like Cygnus modules?

I think there would need to be dedicated construction assets that would need to be put in place before construction starts, such as a housing module (I'm assuming humans will be required), construction arms and mobility systems, and tugs (plus whatever infrastructure they require). Then you'd be ready to accept material deliveries from Earth (or wherever) and be able to assemble or attach them to whatever you're building.

Quote
Does the propulsion portion stay attached forever, or does it detatch and reenter?

As of today we don't have a 100% reusable transportation system to space and back to Earth. So as of today there would be a lot of waste. Hopefully that can change with the ITS and other reusable systems, but if we wanted to build something big in space today we should price into it a lot of expendable hardware.

Quote
I am looking at this from a commodity aspect.  Assume SpaceX is flying the 9m ITSy at the rates they want to fly it. Assume its the lowest cost option. Does it make sense to launch smaller self-propelled modules on more expensive rockets, or to launch larger more capable modules on ITSy?  If so, what will engineers do with that capability?

Depends on what is being built, but I think the faster we standardize on modular in-space construction using reusable transportation systems, the faster we'll be able to expand out into space.
If we don't continuously lower the cost to access space, how are we ever going to afford to expand humanity out into space?

Offline Cherokee43v6

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In my opinion, the best 'Space Truck' design currently is what SpaceX and Blue Origin are doing/attempting.  Reusable unmanned flight.

Second best is pure cargo heavy lift like SLS delivering high volume/high mass modules for on-orbit assembly.

Combining 'manned' cockpits with in-space cargo delivery is heading down the road of the same set of bad compromises that caused the Shuttle to never live up to its hype.

If a manned presence is required, then a Dragon, Starliner, Dream Chaser, or Orion should fly them separately.
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Offline wannamoonbase

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In my opinion, the best 'Space Truck' design currently is what SpaceX and Blue Origin are doing/attempting.  Reusable unmanned flight.

Second best is pure cargo heavy lift like SLS delivering high volume/high mass modules for on-orbit assembly.

Combining 'manned' cockpits with in-space cargo delivery is heading down the road of the same set of bad compromises that caused the Shuttle to never live up to its hype.

If a manned presence is required, then a Dragon, Starliner, Dream Chaser, or Orion should fly them separately.

Completely agree.  In an age where we're going to have robot cars driving us around we don't need a crewed cargo carrying spacecraft.
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Offline Norm38

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Combining 'manned' cockpits with in-space cargo delivery is heading down the road of the same set of bad compromises that caused the Shuttle to never live up to its hype.

The problems with Shuttle's architecture had nothing to do with having crew on board. And ISS probably wouldn't exist if Shuttle had been unmanned.  What would have hosted the assembly crew for a week?
Cargo vehicles don't have to be manned of course, but that's not the deal breaker.

Offline BobHk

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Well we don't NEED crew on board a automated cargo delivery... even station assembly can be automated to a degree to reduce human casualty probability, every accommodation to crew reduces the size of the module delivered.  A series of fifty ton bigelow like expandable modules strung together would be cool but every thing put up there has to have a mission whether its fuel depot, science, or tourism.  How big does it (station, delivery system for minimum sized modules) need to be? 

Offline Roy_H

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Combining 'manned' cockpits with in-space cargo delivery is heading down the road of the same set of bad compromises that caused the Shuttle to never live up to its hype.

The problems with Shuttle's architecture had nothing to do with having crew on board. And ISS probably wouldn't exist if Shuttle had been unmanned.  What would have hosted the assembly crew for a week?
Cargo vehicles don't have to be manned of course, but that's not the deal breaker.

NASA's original idea was to have a much smaller Shuttle for astronauts only (a larger than Dream Chaser would allow living for week or so) and send all the ISS modules up on a new rocket. It became a political decision when the budget for two new designs was not allowed so they combined it into one big shuttle.
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