What facilities? External arms? Pressurized work rooms? Unpressurized work rooms? Space suits? Large airlocks - able to pass a spaceship? Small airlocks? Docking and/or berthing ports? Habitat for the crew? Habitat for the crews of visiting ships? What sort of tools? Propellant depot to refuel ships? Food shop to sell supplies to visiting ships?
It becomes needed when the first reusable manned tug flies.
Quote from: A_M_Swallow on 02/12/2014 01:20 amIt becomes needed when the first reusable manned tug flies.No, they are not linked. A reusable manned tug is not dependent on a repair hub, especially the first one.
The idea is so far into the future, it is like a lump of clay. It can be anything you want. Until it is determined where the repair hub is and what types of vehicles it will service, the discussion is frivolous.
I have heard of main rocket engines being lit 20 times. Using a set of those may permit a reusable tug to do 10 round trips. However are there any main engines that can do 20 full burns without any maintenance?
The mental image I have is the space equivalent of a car repair garage in a village that is a long way from anywhere.
My two cents is that these kinds of concepts have been overtaken or will be overtaken by Moore's Law, IVHM, and robotic servicing. Only if/when there are radical reductions in the cost of getting and keeping humans in space does human servicing of spacecraft begin to make some sense.
Quote from: A_M_Swallow on 02/12/2014 01:35 amI have heard of main rocket engines being lit 20 times. Using a set of those may permit a reusable tug to do 10 round trips. However are there any main engines that can do 20 full burns without any maintenance?Define main rocket engine, define round trip, define full burn.......QuoteMain rocket engine(s) - the one(s) at the back that provide most of the delta-v. As distinct from the RCS thrusters which are normally smaller and frequently on the sides.Round trip - trip to a destination and back. Definition from Harrap's English Dictionary.Full burn - a burn that lasts a long time but hopefully but may be less than the maximum burn time for a single burn.Some thrusters can fire 1000's of times and for scores of minutes.You have to define your architecture (and include everything) not just the tug before you can make decisions on defining the hub.
Main rocket engine(s) - the one(s) at the back that provide most of the delta-v. As distinct from the RCS thrusters which are normally smaller and frequently on the sides.Round trip - trip to a destination and back. Definition from Harrap's English Dictionary.Full burn - a burn that lasts a long time but hopefully but may be less than the maximum burn time for a single burn.
It doesn't make sense to talk about a inspace repair hub at this time, just like it wasn't the right time to talk about gas/service stations in 1890's.
Where ever the repair robots are kept becomes an inspace repair hub.
The alternative to repairing space craft is to launch expendable space craft.
Apollo used big expensive launch vehicles to launch its expendable space craft.A repair hub may allow the space craft to be launched on an SLS.
After each flight say ~15% of the mass can be replaced using units brought up on cheaper LV.
Quote from: A_M_Swallow on 02/12/2014 01:08 pmWhere ever the repair robots are kept becomes an inspace repair hub.If you examine today's commercial or DARPA satellite servicing proposals and projects, no one is planning to centrally locate or field their servicing spacecraft from a common hub or spacedock. It's an unnecessary, additional cost.QuoteThe alternative to repairing space craft is to launch expendable space craft. Repairable is not the same thing as reusable.
QuoteApollo used big expensive launch vehicles to launch its expendable space craft.A repair hub may allow the space craft to be launched on an SLS.Maybe a typo, but I don't follow the logic here. If one HLV can mount human lunar missions without a repair hub, why can't another?
QuoteAfter each flight say ~15% of the mass can be replaced using units brought up on cheaper LV.If you're saying that a repair hub is a way to get around an HLV like SLS, it's unnecessary. Between AR&D, IVHM, and prop xfer, a spacedock is no longer necessary to assemble and checkout exploration stacks. In fact, I'm not sure that a spacedock was necessary to assemble exploration stacks back in the mid-80s when proposed for space station. But you could at least go back to those studies to understand the reasoning and see if it still applies today.FWIW...
Most current space hardware saves mass by being expendable.
Apollo style architectures are too expensive for regular trips.
No. I allowed use of the SLS, just not every trip.
The village garage can refuel cars.
Cargo LV can lift propellant.
Quote from: A_M_Swallow on 02/12/2014 02:27 pmMost current space hardware saves mass by being expendable.I dunno. To the extent that most current space hardware is comsats, most current space hardware has all the lifetime it needs without a repair hub. Expendable/repairable/reusable sort of misses the point when Moore's Law makes the development and launch of a new satellite more cost effective than continuing to limp along on an old satellite with outdated capabilities.And again, in the narrow applications where salvaging old comsats makes sense, projects like DARPA Phoenix, MDA SIS, or ViviSat MEV don't have any need for a repair hub.{snip}
What orbit is it going to be in?
Quote from: DMeader on 02/12/2014 04:45 pmWhat orbit is it going to be in?That depends on where we are going. The first one will probably be in LEO, with EML-2 and LLO as other possible orbits.
I was not planning on repairing satellites. Son of LEMs possibly.
Quote from: DMeader on 02/12/2014 04:45 pmWhat orbit is it going to be in?The first one will probably be in LEO...
Quote from: A_M_Swallow on 02/12/2014 04:53 pmQuote from: DMeader on 02/12/2014 04:45 pmWhat orbit is it going to be in?The first one will probably be in LEO...Well, which one? Which inclination? Without doing big plane change burns the station wouldn't be accessible to anyone not in that orbit. Are they going to build several of them?Like Jim said, this whole scheme need a lot more thought. It did make for some neat images but so far that's all the good I see.
Quote from: A_M_Swallow on 02/12/2014 04:49 pmI was not planning on repairing satellites. Son of LEMs possibly.But wouldn't we just repair reusable landers on the Moon? As long as we've got a lunar surface infrastructure large enough require enough landers/landings to begin thinking about things like repair hubs, wouldn't we just locate that repair hub on the Moon to leverage that infrastructure? Why create a space station to repair landers when we already have a space station on the Moon that could repair those landers?There would be some penalty to bringing lander parts and tools down the lunar gravity well. But with people and all their attendant needs already supported on the Moon (and probably a local propellant source too), that's probably more efficient than duplicating some of those people and supporting all their attendant needs somewhere in cislunar space.My 2 cents.
[snip]It doesn't make sense to talk about a inspace repair hub at this time, just like it wasn't the right time to talk about gas/service stations in 1890's.
In the far future I imagine spacecraft will be largely modular, so a space dock may not be necessary. Modules will be removed and repaired elsewhere. Repairs and production of replacement modules will occur via ISRU on a lunar or small planetary body that doesn't require a lot of energy to lift modules to the spacecraft in need of repair. It is actually the near future that has more need of a in-space repair facility for the long term maintenance of orbiting satellites.
The big problem with pressurised areas is that if the air gets contaminated it has to be thrown away. At more than $1000 a kilogram that gets expensive very quickly.Reusable landers and transfer vehicles will have to be designed so that ~95% of the electronics and the ECLSS can be accessed from inside the spacecraft. The parts can then enter and leave through the docking port. I suspect that sea ships and submarines have a similar problem.
Money and time can be saved by using the same design of arms, mobile base systems and Dxtres as the ISS.
Quote from: A_M_Swallow on 02/27/2014 08:11 amMoney and time can be saved by using the same design of arms, mobile base systems and Dxtres as the ISS.Not really, a hub won't be built for at least a decade. Much of the knowledge of the construction and design of the MSS will be lost, in addition, there will be parts obsolescence. Any new build will cost as much or more than the original.
Quote from: Jim on 02/27/2014 11:20 amQuote from: A_M_Swallow on 02/27/2014 08:11 amMoney and time can be saved by using the same design of arms, mobile base systems and Dxtres as the ISS.Not really, a hub won't be built for at least a decade. Much of the knowledge of the construction and design of the MSS will be lost, in addition, there will be parts obsolescence. Any new build will cost as much or more than the original. Not quite sure I can agree with you on this one Jim.
Any new build will cost as much or more than the original.
The blue prints for the mechanical parts may be on file somewhere.The main aim of using the original designs is to keep the manufacturing time down to 3 years rather than the 10 years development time projects can take.
Quote from: JasonAW3 on 02/27/2014 07:56 pmQuote from: Jim on 02/27/2014 11:20 amQuote from: A_M_Swallow on 02/27/2014 08:11 amMoney and time can be saved by using the same design of arms, mobile base systems and Dxtres as the ISS.Not really, a hub won't be built for at least a decade. Much of the knowledge of the construction and design of the MSS will be lost, in addition, there will be parts obsolescence. Any new build will cost as much or more than the original. Not quite sure I can agree with you on this one Jim.The MSS is the arm and its mobile base on the ISS
Quote from: Jim on 02/11/2014 10:57 pmThe idea is so far into the future, it is like a lump of clay. It can be anything you want. Until it is determined where the repair hub is and what types of vehicles it will service, the discussion is frivolous. Nahhhh.... You gotta believe. I've already designed the structure. Apologies for the crude video.
Quote from: JohnFornaro on 02/26/2014 05:37 pmQuote from: Jim on 02/11/2014 10:57 pmThe idea is so far into the future, it is like a lump of clay. It can be anything you want. Until it is determined where the repair hub is and what types of vehicles it will service, the discussion is frivolous. Nahhhh.... You gotta believe. I've already designed the structure. Apologies for the crude video.In LEO the hub would be repairing transfer vehicles and space tugs. In LLO and EML-1/2 the hub would be repairing reusable lunar landers.It may be possible to use CubeSats to reduce the risk. Launching requires the hub to fit into a fairing but to contain a spaceship it needs to be wider than a spaceship. The proposed cure is to launch it flat and expand in space. A CubeSat sized mini module that shows the opening and locking mechanism works can be built and launched cheaply. A second satellite that contains a full sized joint can test that.