My first thought was thin film arrays as a layer of an inflatable structure. Which begs, how do you deflate for storage in a vacuum? Shape memory? How do you patch it? Self-sealing layer?
Radiators could be fitted into the skin, like they are in Dragon's trunk. Also, with emissivity management, radiators may not even be required.
Now he said that the ships were rendered from actual CAD models of what they plan to build.
Quote from: Robotbeat on 11/05/2016 04:53 pmRadiators could be fitted into the skin, like they are in Dragon's trunk. Also, with emissivity management, radiators may not even be required.Dragon not relevant. It is has low power consumption and not manned. Radiators will be required. And more than the body surface area.
I read the design as having the radiator fins as the stiffeners, and the PV array stretched between them.How it deploys and stows is beyond me. An EVA?!
The fins see each other so that isn't so efficient. More acreage is then required
Wings & RingsThe ITS animation suggests, to me at least, that a wing's booms are deployed and retracted on a ring ~14 m in diameter. In retraction the thin-film PV accordion-folds loosely in the space between the 14 m ring and the 17 m hull. Each wing is attached to its own ring, one stacked above the other, operating in counter-rotation.
Quote from: wstewart on 11/05/2016 06:38 pmWings & RingsThe ITS animation suggests, to me at least, that a wing's booms are deployed and retracted on a ring ~14 m in diameter. In retraction the thin-film PV accordion-folds loosely in the space between the 14 m ring and the 17 m hull. Each wing is attached to its own ring, one stacked above the other, operating in counter-rotation.The SpaceX-provided animation (at 2:45) shows the extension, but obfuscates the causal mechanism. Your theory is interesting. I'm not quite groking how your postulated ring mechanism would work. Could you sketch it?
Quote from: LMT on 11/05/2016 06:38 pmWings & RingsThe ITS animation suggests, to me at least, that a wing's booms are deployed and retracted on a ring ~14 m in diameter. In retraction the thin-film PV accordion-folds loosely in the space between the 14 m ring and the 17 m hull. Each wing is attached to its own ring, one stacked above the other, operating in counter-rotation.The SpaceX-provided animation (at 2:45) shows the extension, but obfuscates the causal mechanism. Your theory is interesting. I'm not quite groking how your postulated ring mechanism would work. Could you sketch it?
The images Musk presented of the ITS spaceship have a very particular solar panel design shown.Now he said that the ships were rendered from actual CAD models of what they plan to build. Taking that as a given, and not using this thread to try and design some new/better/my-favorite-type-of solar panels, let's start examining the engineering of spaceship internals required to support such a design.First question: extension and retraction. How might one design the spaceship internals necessary to make such panels possible: launch secure, reliable extension, sufficiently strong for the loads encountered in some ship maneuvers, with straightforward and robust panel retraction at Mars? Where would the panels fit inside the ship and around the tankage/engines that were shown in the image?
Quote from: Jim on 11/05/2016 02:59 pmThe fins see each other so that isn't so efficient. More acreage is then requiredThey see each other, but over a relatively small angle, judging by the proportion.
Quote from: Llian Rhydderch on 11/05/2016 11:11 amThe images Musk presented of the ITS spaceship have a very particular solar panel design shown.Now he said that the ships were rendered from actual CAD models of what they plan to build. Taking that as a given, and not using this thread to try and design some new/better/my-favorite-type-of solar panels, let's start examining the engineering of spaceship internals required to support such a design.First question: extension and retraction. How might one design the spaceship internals necessary to make such panels possible: launch secure, reliable extension, sufficiently strong for the loads encountered in some ship maneuvers, with straightforward and robust panel retraction at Mars? Where would the panels fit inside the ship and around the tankage/engines that were shown in the image?Indeed it does look odd. So they extend from the rear at 90deg to the body, then fan out and we can see the stiffening ribs from this PoV.Logically the stiffening ribs should be behind the surface to avoid shadowing some of the array area. Other points will be that since no PV array is 100% efficient where does the heat go and how big is the "hotel" load (from the people inside) those radiators have to dump as well. The panels are very long so one option is they are laying inside the skin of the vehicle and being bent through 90deg during deployment. One idea would be if the panels are thin film the heat they cannot convert to electricity is directly radiated from the back surface, eliminating a specific radiator structure. likewise TF arrays make the stiffeners smaller.A possible concept would be TF arrays between the ribs and the ribs being inflatable tubes. Keep in mind the inflatable rescue slides on aircraft for an idea of how strong quite lightweight low pressure structures can be.The joker in the pack for inflatable systems is controlled re-packing for descent, which this system will also have to do. There are a number of technologies for deploying long rigid spars from small containers (search "aerospace mechanisms" ). It helps if you can avoid having a heavy point mass at the far end of the structure away from the deployment mechanism. The sequence is also important. IIRC these go to full length, then fan out, not the other way around.
Quote from: meekGee on 11/05/2016 07:46 pmQuote from: Jim on 11/05/2016 02:59 pmThe fins see each other so that isn't so efficient. More acreage is then requiredThey see each other, but over a relatively small angle, judging by the proportion. No, each individual fin (except for the end ones) is looking at two fins next to it. And at the base, they are wider and closer.
The thermal radiation is isotropic. (Well, depending on the surface) and so what the fin cares about is "how big an angle of the sky is "space".As someone notes above, the ribs are backwards anyway.
Quote from: meekGee on 11/06/2016 12:05 pmThe thermal radiation is isotropic. (Well, depending on the surface) and so what the fin cares about is "how big an angle of the sky is "space".As someone notes above, the ribs are backwards anyway.And the ribs are a large portion of that "space"They can't be backwards, otherwise the vehicle would be in the view too.
As said above, the area the solar panels deploy out of seems way too full of other gear to squeeze the panels and deployment mechanism into. Does anybody have any idea why they would be way back there instead of between upper most tank and cargo? Center of gravity issues? Does not make sense to me.Matthew
As said above, the area the solar panels deploy out of seems way too full of other gear to squeeze the panels and deployment mechanism into. Does anybody have any idea why they would be way back there instead of between upper most tank and cargo? Center of gravity issues? Does not make sense to me.
Quote from: Robotbeat on 11/05/2016 04:53 pmRadiators could be fitted into the skin, like they are in Dragon's trunk. Also, with emissivity management, radiators may not even be required.Notably, recent heat pipe designs can reject spacecraft heat with a capability exceeding 50 W/cm2, which is a remarkable efficiency. I think this frees the wing booms from that job, potentially saving much complexity in wing design.
Just a thought: The solar array positioned at the base of ITS makes me think that SpaceX perhaps considers dual-use, i.e. en route and on the surface. How that could be done I don't know, but deployment by inflation could be part of the solution I guess.
What if the panels have those ultra flexible carbon rods in them, full length. The rods spread out like a fan, but can be pulled back into the ship.Deployment from a folded state would work well, but I can't see how stowing would work.
Which would fit in with Musks inflatable roll-out array statement.
Technology testingThe U.S. Air Force has funded a test flight of the ROSA mechanism, now scheduled for a SpaceX launch in Spring 2017 to the International Space Station, where it will be deployed in space.
I was thinking it would work like a paper fan, with thin CF stays. One reason to make the stays tapered would be to keep the thickness of the packed fan more uniform.
That tapering would make sense if SpaceX plans to open the wings when the ITS is landed on the martian surface, where a tapered cantilever beam would reduce the wing's bend. Otherwise the tapering serves no purpose that's obvious to me.
The back of a solar panel must be high emissivity as a solar panel is basically its own radiator. It must reject heat like any other power conversion device and like other power conversion devices it works better and lasts longer if it can be kept cool.I don't think the ribs are radiators.I disagree with Jim because the body of the ITS should be capable of rejecting hundreds of kilowatts HOWEVER I kind of also agree with him that other radiators may be needed since the body needs to protect against some reentry heat, and I think integrating a radiator that can also operate at high temperatures and be insulating to those temperatures would be a big challenge such that you're probably better off just using deployable radiators.
Quote from: Jim on 11/05/2016 05:20 pmQuote from: Robotbeat on 11/05/2016 04:53 pmRadiators could be fitted into the skin, like they are in Dragon's trunk. Also, with emissivity management, radiators may not even be required.Dragon not relevant. It is has low power consumption and not manned. Radiators will be required. And more than the body surface area.Somebody did some maths on this: https://thephysicsofspacex.wordpress.com/2016/10/31/thermal-management-aboard-the-its/Don't know, whether the calculations are correct.
Quote from: LMT on 11/08/2016 12:39 amThat tapering would make sense if SpaceX plans to open the wings when the ITS is landed on the martian surface, where a tapered cantilever beam would reduce the wing's bend. Otherwise the tapering serves no purpose that's obvious to me.IIRC the assumed sun-facing side of the array is the bottom - works with motors toward the sun. Deploying on the surface would have them upside-down. (Maybe they can be removed and flipped?)
But the ITS's solar arrays would only supply ~1/20th of the power on Mars as would be needed for refueling a single ITS.
Need about 1MW of electricity average. So about 6MW of solar.
Quote from: Robotbeat on 11/08/2016 05:54 amNeed about 1MW of electricity average. So about 6MW of solar.Please give refs or calcs, to flesh out a realistic scenario. (For propellant production, not for solar panel sunlight.)
I did some work on power and cooling for the ITS, when it was the BFS. A bit out of date since I expected radiators in the cargo bay doors, as per the space shuttle.
Notably, recent heat pipe designs can reject spacecraft heat with a capability exceeding 50 W/cm2, which is a remarkable efficiency. I think this frees the wing booms from that job, potentially saving much complexity in wing design.
Quote from: lamontagne on 11/08/2016 03:39 amI did some work on power and cooling for the ITS, when it was the BFS. A bit out of date since I expected radiators in the cargo bay doors, as per the space shuttle.Not really out of the question yet. wstewart earlier suggested radiators that could achieve on the order of 50 W/cm2 of heat transfer, here:Quote from: wstewart on 11/06/2016 04:10 pmNotably, recent heat pipe designs can reject spacecraft heat with a capability exceeding 50 W/cm2, which is a remarkable efficiency. I think this frees the wing booms from that job, potentially saving much complexity in wing design.
Quote from: Llian Rhydderch on 11/08/2016 02:18 pmQuote from: lamontagne on 11/08/2016 03:39 amI did some work on power and cooling for the ITS, when it was the BFS. A bit out of date since I expected radiators in the cargo bay doors, as per the space shuttle.Not really out of the question yet. LMT earlier suggested radiators that could achieve on the order of 50 W/cm2 of heat transfer, here:Quote from: LMT on 11/06/2016 04:10 pmNotably, recent heat pipe designs can reject spacecraft heat with a capability exceeding 50 W/cm2, which is a remarkable efficiency. I think this frees the wing booms from that job, potentially saving much complexity in wing design.The 50 w/cm2 cited there is the heat flux through a heat pipe cross-section, not radiative heat rejection per radiator area.Heat radiation is a function of temperature; to radiate 50 w/cm2 to a near absolute zero sink the radiator has to be over 1200 degrees C.
Quote from: lamontagne on 11/08/2016 03:39 amI did some work on power and cooling for the ITS, when it was the BFS. A bit out of date since I expected radiators in the cargo bay doors, as per the space shuttle.Not really out of the question yet. LMT earlier suggested radiators that could achieve on the order of 50 W/cm2 of heat transfer, here:Quote from: LMT on 11/06/2016 04:10 pmNotably, recent heat pipe designs can reject spacecraft heat with a capability exceeding 50 W/cm2, which is a remarkable efficiency. I think this frees the wing booms from that job, potentially saving much complexity in wing design.