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#11
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Two Starships in "bolas" rotation
In article ,
says... Clearly, especially since the current NASA plan of record doesn't include Starship in any meaningful way. It still relies heavily on SLS/Orion, so we will be limited to one crewed mission per year. That's pretty weak sauce considering how "close" the moon is. Starship doesn't fit their desired architecture. Once they admit that Starship is real, all their plans and hardware go into a cocked hat. If you think the graphic Musk showed of Starship docked to ISS looked a little silly, imagine the same thing with the much smaller Gateway. This image is worth a thousand words: https://i.redd.it/64h5zvj1gex21.jpg It's part of this discussion: https://www.reddit.com/r/SpaceXLoung...ex_vs_blue_ori gin_2024_aspirations/ I think that the scale of Starship is something I think most people won't be able to wrap their mind around. It's just so fracking huge compared to anything planned by anyone to land crew on the moon or Mars that it's not even funny. SpaceX needs Starlink for the potential revenue to attract investors to develop Starship/Super Heavy. But SpaceX also needs Starship/Super Heavy to launch and maintain the Starlink constellation. You're starting to make this sound like trying to fly by tugging on your own bootstraps. SpaceX has gotten over a billion in investment and it is ALL going to StarLink (and none to Starship/Falcon Super Heavy). Agreed. Starlink must come first. That's a huge potential revenue stream that they'll need in order to fund a moon/Mars capable Starship. Mars is still Musk's ultimate goal, but Starlink will need to come first in order to provide the massive cash flow needed to turn Starship from a cargo launcher into a true crewed spaceship capable of performing an actual Mars mission. IMHO, of course. While I think Musk is overly optimistic (as usual), I think you are overly pessimistic. I'd bet on a manned Mars mission before 2030 with the potential for lunar missions before that. 2030 for a first crewed Mars mission is certainly optimistic, IMHO. I'd love to see that. And I think it might just be possible if enough development money is spent in all the right areas. But I also think it's safe to say that if this were any other online forum, we'd both be called a SpaceX fanboys and our opinions would be widely ridiculed. Until Starship/Super Booster start flying "routinely", the nay-sayers will keep saying that all of Musk's Mars aspirations are an Internet billionaire's fantasy. I'm also sure they'd say the same of Jeff Bezos's aspiration to start moving industry off earth and into space. That's what motivated him to start Blue Origin. 05.09.19 Jeff Bezos wants to save Earth by moving industry to space The billionaire owner of Blue Origin outlines plans for mining, manufacturing, and colonies in space. https://www.fastcompany.com/90347364...save-earth-by- moving-industry-to-space Jeff -- All opinions posted by me on Usenet News are mine, and mine alone. These posts do not reflect the opinions of my family, friends, employer, or any organization that I am a member of. |
#12
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Two Starships in "bolas" rotation
William Elliot wrote on Mon, 27 May 2019 00:28:16
-0700: On Sun, 26 May 2019, Fred J. McCall wrote: Jeff Findley wrote on Sun, 26 May 2019 And keep in mind the lifetime of these satellites is relatively short (from memory something like 3-5 years), so this isn't a "one time" thing. If Starlink is successful, SpaceX will be continuously launching its own Starlink satellites for some time to come. Yep. They're going to have to replace something like 2500 satellites a year once the full system is up. A huge investement that has to constantly tread water? Insanity! Perhaps, but they're hardly the only ones building up such a system so there's probably money to be made there. -- "The reasonable man adapts himself to the world; the unreasonable man persists in trying to adapt the world to himself. Therefore, all progress depends on the unreasonable man." --George Bernard Shaw |
#13
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Two Starships in "bolas" rotation
Jeff Findley wrote on Mon, 27 May 2019
07:20:24 -0400: In article , says... Clearly, especially since the current NASA plan of record doesn't include Starship in any meaningful way. It still relies heavily on SLS/Orion, so we will be limited to one crewed mission per year. That's pretty weak sauce considering how "close" the moon is. Starship doesn't fit their desired architecture. Once they admit that Starship is real, all their plans and hardware go into a cocked hat. If you think the graphic Musk showed of Starship docked to ISS looked a little silly, imagine the same thing with the much smaller Gateway. This image is worth a thousand words: https://i.redd.it/64h5zvj1gex21.jpg It's part of this discussion: https://www.reddit.com/r/SpaceXLoung...ex_vs_blue_ori gin_2024_aspirations/ I think that the scale of Starship is something I think most people won't be able to wrap their mind around. It's just so fracking huge compared to anything planned by anyone to land crew on the moon or Mars that it's not even funny. Yep, 100 tonnes of cargo from Earth to lunar surface and a return to Earth without requiring refueling other than in LEO vs something like 6.7 tonnes of cargo (4 in the original version without 'stretch tanks') to lunar surface, toss the lander part, and refuel the Ascent Element and Transfer Element in L2 Halo. SpaceX needs Starlink for the potential revenue to attract investors to develop Starship/Super Heavy. But SpaceX also needs Starship/Super Heavy to launch and maintain the Starlink constellation. You're starting to make this sound like trying to fly by tugging on your own bootstraps. SpaceX has gotten over a billion in investment and it is ALL going to StarLink (and none to Starship/Falcon Super Heavy). Agreed. Starlink must come first. That's a huge potential revenue stream that they'll need in order to fund a moon/Mars capable Starship. I think they could get it funded without StarLink, although that would require dumping pretty much all their profit for half a dozen years into Starship/Falcon Super Heavy. StarLink is a money sink for a fair number of years, regardless. Mars is still Musk's ultimate goal, but Starlink will need to come first in order to provide the massive cash flow needed to turn Starship from a cargo launcher into a true crewed spaceship capable of performing an actual Mars mission. IMHO, of course. While I think Musk is overly optimistic (as usual), I think you are overly pessimistic. I'd bet on a manned Mars mission before 2030 with the potential for lunar missions before that. 2030 for a first crewed Mars mission is certainly optimistic, IMHO. I'd love to see that. And I think it might just be possible if enough development money is spent in all the right areas. Musk's schedule is a pair of cargo ships in 2022 and first manned mission in 2024. Remember his statement that he thinks you ought to be able to accomplish anything in five years because that's almost forever. I think expecting things to take twice as long as his schedule isn't unreasonable, so 2028-2030 for a manned mission feels about right to me. But I also think it's safe to say that if this were any other online forum, we'd both be called a SpaceX fanboys and our opinions would be widely ridiculed. I tend to be pretty insensitive to what other people think when it comes to arriving at my views. If I was a "SpaceX fanboy" I'd be accepting Musk's schedule rather than assuming everything is going to slide several conjunctions. Until Starship/Super Booster start flying "routinely", the nay-sayers will keep saying that all of Musk's Mars aspirations are an Internet billionaire's fantasy. So was SpaceX... I'm also sure they'd say the same of Jeff Bezos's aspiration to start moving industry off earth and into space. That's what motivated him to start Blue Origin. 05.09.19 Jeff Bezos wants to save Earth by moving industry to space The billionaire owner of Blue Origin outlines plans for mining, manufacturing, and colonies in space. https://www.fastcompany.com/90347364...save-earth-by- moving-industry-to-space I tend to have more faith in Bezo's schedule estimates than in Musk's because at least up to now he has a history of being pretty conservative. He says he can have Blue Moon and a lunar Ascent Element ready to go to support a manned lunar landing in 2024 (with cargo landings using just Blue Moon in 2023). Bezos is, at least for now, aimed squarely at the Moon, as you can infer from the name of his next booster after New Glenn. -- "The reasonable man adapts himself to the world; the unreasonable man persists in trying to adapt the world to himself. Therefore, all progress depends on the unreasonable man." --George Bernard Shaw |
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Two Starships in "bolas" rotation
On Tuesday, May 21, 2019 at 2:15:19 PM UTC-4, Niklas Holsti wrote:
The SpaceX plans for the first Mars trips involve two Starships making the trip at the same time. The SpaceX videos show a Starship flying alone, in a fixed attitude (pointing away from the Sun) thus in free fall. From other sources there is some concern that a multi-month weightless trip may incapacitate the pilots and passengers, for example resulting in blurred vision when they are again subjected to acceleration or gravity. Here I propose a possible solution: cable the two Starships together in a nose-to-nose attitude and rotate them to provide simulated gravity during the trip. Do you have any numbers on this? How much propellant would be necessary to spin up the rotation? Would it be necessary to despin them upon arrival, or are you going to just cut the cable and let the two ships float off into different orbits? |
#15
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Two Starships in "bolas" rotation
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#16
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Two Starships in "bolas" rotation
On 7/26/2019 12:58 PM, Niklas Holsti wrote:
On 19-07-24 20:18 , wrote: On Tuesday, May 21, 2019 at 2:15:19 PM UTC-4, Niklas Holsti wrote: The SpaceX plans for the first Mars trips involve two Starships making the trip at the same time. The SpaceX videos show a Starship flying alone, in a fixed attitude (pointing away from the Sun) thus in free fall. From other sources there is some concern that a multi-month weightless trip may incapacitate the pilots and passengers, for example resulting in blurred vision when they are again subjected to acceleration or gravity. Here I propose a possible solution: cable the two Starships together in a nose-to-nose attitude and rotate them to provide simulated gravity during the trip. Do you have any numbers on this? How much propellant would be necessary to spin up the rotation? Assuming a 50 m radius of rotation and a desired acceleration (pseudo-gravity) of 3 m/s/s, a rotational speed of about 12.2 m/s is enough. So quite small compared to orbital velocities. Have you calculated as to whether it would be necessary to use curved decks to preserve gravity normal vectors across the entire radius of deck surface that would be off-axis from the rotation? I suppose it would depend on the rotational radius. If the radius is long enough the length of the decks may not matter as they wouldn't extend far enough to experience any off-axis effects since they are too small a section of the circumference thus they could remain flat. Also let's not forget the centrifuge approach ala the movie 2001: A Space Odyssey. One (or two) sections of the Starship could be put in (counter)rotation to provide artificial gravity within the section(s). It does introduce issues of vibration and spacecraft stability. Or even more simply, just put the spacecraft into a spin along the flight path vector. Thus no 2nd ship required or fancy rendezvous and un-tether maneuvers needed. This would also allow incremental build-up of spacecraft by joining future Starships together in LEO to make a larger spacecraft. It's fun to speculate. None of this would be needed for trips to and from the Moon. The flight is just not that long. Underlying all of lunar & planetary habitation is the assumption that the human body does not develop strange new diseases from not being in 1G, or that there is some conditioning (PT) needed near 1G to stave off these effects. Subsequent generations, if born in that environment might not need that, but might not be able to comfortably live back on Earth either. Data points we just don't have right now. Dave |
#17
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Two Starships in "bolas" rotation
On 19-07-26 20:54 , David Spain wrote:
On 7/26/2019 12:58 PM, Niklas Holsti wrote: On 19-07-24 20:18 , wrote: On Tuesday, May 21, 2019 at 2:15:19 PM UTC-4, Niklas Holsti wrote: The SpaceX plans for the first Mars trips involve two Starships making the trip at the same time. The SpaceX videos show a Starship flying alone, in a fixed attitude (pointing away from the Sun) thus in free fall. From other sources there is some concern that a multi-month weightless trip may incapacitate the pilots and passengers, for example resulting in blurred vision when they are again subjected to acceleration or gravity. Here I propose a possible solution: cable the two Starships together in a nose-to-nose attitude and rotate them to provide simulated gravity during the trip. Do you have any numbers on this? How much propellant would be necessary to spin up the rotation? Assuming a 50 m radius of rotation and a desired acceleration (pseudo-gravity) of 3 m/s/s, a rotational speed of about 12.2 m/s is enough. So quite small compared to orbital velocities. Have you calculated as to whether it would be necessary to use curved decks to preserve gravity normal vectors across the entire radius of deck surface that would be off-axis from the rotation? If the Starship outer diameter is 9 m, the inside walls are perhaps 4 m from the ship's center. With a 50 m radius of rotation, the centripetal acceleration at 4 m from the ship's centerline is tilted by some 4.6 degrees to the ship's long axis (that is, to the "vertical" at ship's center). This is clearly noticeable but I think it would be tolerable. However, you shouldn't fill your soup-plate to the very edge and then set it down on a table close to the ship's wall... leave some free-board and take "seconds" instead. Or the table could have some adjustable levelling mechanism. Better keep the decks flat, I think. I suppose it would depend on the rotational radius. Doubling the rotational radius halves the off-axis angles, but increases the required velocity by sqrt(2). Also let's not forget the centrifuge approach ala the movie 2001: A Space Odyssey. One (or two) sections of the Starship could be put in (counter)rotation to provide artificial gravity within the section(s). It does introduce issues of vibration and spacecraft stability. That would require major changes to Starship design, or meet with the same problems as the next suggestion: Or even more simply, just put the spacecraft into a spin along the flight path vector. Thus no 2nd ship required or fancy rendezvous and un-tether maneuvers needed. Spinning (rolling) around the long axis would give a rotational radius of only 4.5 m, max, giving disorientating Coriolis and other effects. The pseudogravity would be radial, 90 degrees offset from the real longitudinal gravity when the ship stands on its rear fins. Not good, IMO. This would also allow incremental build-up of spacecraft by joining future Starships together in LEO to make a larger spacecraft. I don't understand how the spin/roll is related to incremental joining of Starships. In a Starship, one end "kicks" (the aft end) and the other "penetrates" (the front end); they are not easily connected together to form a larger living space. At most, one could dock two Starships front-to-front. Can you clarify what you mean? Underlying all of lunar & planetary habitation is the assumption that the human body does not develop strange new diseases from not being in 1G, or that there is some conditioning (PT) needed near 1G to stave off these effects. Subsequent generations, if born in that environment might not need that, but might not be able to comfortably live back on Earth either. Data points we just don't have right now. Yes, it's a shame that there is no pseudogravity experiment on the ISS. It seems one was planned, but then cancelled (https://en.wikipedia.org/wiki/Centri...ations_Module), but it would have been too small for human use anyway. -- Niklas Holsti Tidorum Ltd niklas holsti tidorum fi . @ . |
#18
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Two Starships in "bolas" rotation
I have an update for you Niklas.
Here's a fellow (smallstars) who has proposed an artificial gravity system based on the same physical principles you rely on but uses a third Starship as a cargo and axis vehicle that holds an bi-directional extruding truss system to attach the remaining two crewed Starships. The rigid structure allows each Starship to pivot on its own pitch axis to align them for a short Raptor burn to initiate and terminate rotation. Then they can pivot so that the pitch axis aligns with the rotational hub to provide the artificial gravity within the Starship for the months long journey outbound and inbound. At either destination the crewed Starships detach from the hub for landing. The hub ship also lands robotically for refueling and reuse. See: https://www.youtube.com/watch?v=3CRiJTJikjk Dave |
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Two Starships in "bolas" rotation
On 2019-05-21 2:15 PM, Niklas Holsti wrote:
So that's the suggestion. Comments are welcome... The other popular scheme is attaching two Starships end-to-end rather than nose-to-nose. Speed of rotation would have to be faster though, unless a tether or truss is used to increase separation, and I don't know if the induced Coriolis forces would be a problem. Also for the duration of the transit, up and down would be reversed, but other's don't think having inverted decks with furniture mounted or stowed on the 'ceiling' during transit and vise-versa 'on the ground' would be an issue. This scheme would require RCS systems used to induce rotation vs the Raptors, since they are now unusable after docking and during coast and that might also be an issue. With nose-to-nose it might be possible to use the sea-level Raptors to gimbal enough to provide the side thrust needed to induce and remove rotation, even if less efficient in vacuum. Not that much thrust is needed. Dave |
#20
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Two Starships in "bolas" rotation
On 2019-07-26 2:44 PM, Niklas Holsti wrote:
On 19-07-26 20:54 , David Spain wrote: Or even more simply, just put the spacecraft into a spin along the flight path vector. Thus no 2nd ship required or fancy rendezvous and un-tether maneuvers needed. Spinning (rolling) around the long axis would give a rotational radius of only 4.5 m, max, giving disorientating Coriolis and other effects. The pseudogravity would be radial, 90 degrees offset from the real longitudinal gravity when the ship stands on its rear fins. Not good, IMO. The centrifuge in Discovery was small in radius since it had to be contained within the pressure sphere of the hull (12.2 meters). I wonder if AC Clarke had done the math on that? https://en.wikipedia.org/wiki/Discovery_One This would also allow incremental build-up of spacecraft by joining future Starships together in LEO to make a larger spacecraft. I don't understand how the spin/roll is related to incremental joining of Starships. In a Starship, one end "kicks" (the aft end) and the other "penetrates" (the front end); they are not easily connected together to form a larger living space. At most, one could dock two Starships front-to-front. Can you clarify what you mean? Yes you can dock front-to-front. If fact, what if you dock to a habitation module like a large inflatable Bigelow module? Once in orbit the nose of a Starship docks to an already inflated an constructed habitation module where the diameter expands to 20-30 meters and the circular 'decks' run parallel to each other along the inner circumference. Now you have an artificial gravity environment where the rate of roll is much, much less to achieve a given gravity and you get this without needing a 2nd Starship and all the complexity of trying to counterbalance two Starships. Of course two Starships could share this hab module if docked at each end. The habitation module would remain in orbit and not land but could be reused from either destination. Also if the roll rate is small enough it might be possible to work within the original Starship cabins under micro-gravity where the role of walls vs floors are inverted during transit, but because the Starship cabins are much closer to the axis of rotation there is very little gravity here. None along the center line of the Starship. A downside would be that this might require a 2nd Starship to attach to the first Starship in Earth orbit to give it the boost it needs for TMI. Depends on the mass of the hab module vs Starship's propulsion budget, which is probably tight already. If the math works, it might be possible that the 2nd Starship only gets the configuration into an elliptical orbit high enough that the enhanced 1st Starship and hab can 'kick' into Hohmann orbit at apogee after separation from 2nd Starship which can then return to Earth. Of course there is the 'hab as a cycler' scenario which avoids this, but puts more maneuver burden on Starship. And the added complexity of launching and maintaining a cycler, which is NOT on SpaceX's drawing board today (and neither is a hab I might add). This might also require a change to the possible Mars arrival navigation scenario in that Starship(s) would need first to slow into orbit around their destination first in order to detach the hab module and then descend. Rather than a direct descent trajectory. Which requires more fuel, etc. OR you de-roll and detach just before arrival and have the hab module have its own propulsion to place it into orbit. That puts less on Starship but far more on the hab module, plus now you have to figure out how to refuel it for the return if it can't contain or preserve enough fuel for both legs of the journey. A way to help this issue is if the hab goes up 'unfurnished'. Meaning the bulk of the supplies for life support and habitation are brought up in Starship. Moved into the hab during transit and then stowed back into Starship upon arrival. It's going to be needed on the surface anyway, not wasted hanging out in orbit. Anything that can reduce the mass of the hab is a win in general. The main reason I like this scheme is that it places far less burden on changes and potential stresses to Starship itself and fancy in-space maneuvers and configurations, over more straightforward docking and roll. There are a TON of issues remaining to get crewed Starships to Mars. For starters I think Elon is totally underestimating the complexity of a working life support system that can sustain for the months needed if in a Hohmann transfer orbit let alone once on Mars for a year or so. The hab scheme gives you artificial gravity but doesn't simplify the life support issue, just the opposite. No matter how you slice it, there is complexity to artificial gravity. I have the sneaking suspicion that EM thinks this can be short circuited by routine exercise inside a Starship. If I can compensate for the deleterious effects using exercise, drugs, or alcohol (lol) well... 'tight is right'. :-) I've reflected on these issues before, which given what SpaceX is doing vs some of the still to be resolved issues for Mars & Mars transit, makes me think the Moon is still much less of a harsh mistress and the hidden agenda here. Dave |
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