"Maybe it's foolhardy, but we're going to do it anyway..."I mean, surely there's a better way...
At Exodus, we're creating a small (washing-machine sized), deployable, "space-origami" structure that can fold up within a long narrow rocket payload bay, and fold out to a segmented, rigid toroid array. Single launch, no in-space assembly. I think we've also got some pretty neat mechanisms to control spin orientation and spin rate.Most importantly, we're looking at all the applications (terrestrial and space-based) where we can start making money from these designs before we even try to scale the concept up to space station size to address the biomedical questions.
Richie-5Quote from: LMT on 07/31/2018 02:38 amSimplified Richie-class ITS ConfigurationThe initial "Richie-class" options could support concurrent AG tests - for multiple concurrent mission profiles - in low g, Mars g and Earth g. Each mission crew would switch between AG environments at each simulated mission AG transition: e.g. transition from in-transit low g to Mars surface g, or from Mars surface g to Mars surface centrifuge Earth g. All system hardware could be returned to Earth for repair or modification between each experimental run, and then repurposed for deep-space missions at the end of AG testing.To get greater value out of 5 ITS craft, you could tweak that Richie-class config to get 5 different, concurrent AG environments. This would enable concurrent AG testing of missions to all bodies between Earth and Mars.The 5 AG environments:1. Earth g2. Mars g3. Lunar g4. Deimos g5. low g5 ITS craft for 5 AG environments, with all appreciable g environments located on the ceiling: "Richie-5", one might say.
Simplified Richie-class ITS ConfigurationThe initial "Richie-class" options could support concurrent AG tests - for multiple concurrent mission profiles - in low g, Mars g and Earth g. Each mission crew would switch between AG environments at each simulated mission AG transition: e.g. transition from in-transit low g to Mars surface g, or from Mars surface g to Mars surface centrifuge Earth g. All system hardware could be returned to Earth for repair or modification between each experimental run, and then repurposed for deep-space missions at the end of AG testing.
Quote from: LMT on 08/01/2018 03:30 pmRichie-5Quote from: LMT on 07/31/2018 02:38 amSimplified Richie-class ITS ConfigurationThe initial "Richie-class" options could support concurrent AG tests - for multiple concurrent mission profiles - in low g, Mars g and Earth g. Each mission crew would switch between AG environments at each simulated mission AG transition: e.g. transition from in-transit low g to Mars surface g, or from Mars surface g to Mars surface centrifuge Earth g. All system hardware could be returned to Earth for repair or modification between each experimental run, and then repurposed for deep-space missions at the end of AG testing.To get greater value out of 5 ITS craft, you could tweak that Richie-class config to get 5 different, concurrent AG environments. This would enable concurrent AG testing of missions to all bodies between Earth and Mars.The 5 AG environments:1. Earth g2. Mars g3. Lunar g4. Deimos g5. low g5 ITS craft for 5 AG environments, with all appreciable g environments located on the ceiling: "Richie-5", one might say.4 or 5 BFS is kind of pricey.
How would setup an AG station if only 2 BFS were available?
And remember: leasing is an option with Richie-class systems.
Best way to get an AG research station built is to convince Elon Musk that SpaceX needs to do the research before going to Mars.
Quote from: LMT on 08/01/2018 05:49 pmAnd remember: leasing is an option with Richie-class systems.Not really. To get decent data, you'd need them for at least 2 years, ideally more. That means you're pulling 4 BFSes out of service for that entire time. In addition, you have time on the ground needed for the modifications necessary for your structure. (Two BFSes "upright", two "upside down". The tail-tail mating. Etc.) I think SpaceX would consider it a waste of ships.So, as I said, you'd be buying the ships. Or leasing on such harsh terms that you are effectively paying their replacement cost over two years.
Quote from: Paul451 on 08/02/2018 01:46 amSo, as I said, you'd be buying the ships. Or leasing on such harsh terms that you are effectively paying their replacement cost over two years.Oh, you've considered how and why big-ship leasing works? Cool. Do give us some case studies, and compare/contrast.
So, as I said, you'd be buying the ships. Or leasing on such harsh terms that you are effectively paying their replacement cost over two years.
Quote from: RonM on 08/01/2018 04:30 pmHow would setup an AG station if only 2 BFS were available?It's the premise of yesterday's post, with use as illustrated. See the schedule.
mikelepage, would you feel like adjudicating this little "challenge", if anyone bothers with it?
With a radius of 28-48m they would be able to simulate Mars G or higher at low spin rates which should be well within the tolerances of the interstage docking clamps, and without any of the potential dynamic issues of nose-to-nose tethered connections.
Also a small correction - there's no need to depict refueling of BFR in low Mars orbit - one full tank on Mars surface is enough to get all the way home so it should just launch directly to the interplanetary transit back to Earth.
The proper forum for expanded brainstorming like this is to write a paper and submit it to a journal for publication, or set up a website
Who's Richie?
Quote from: mikelepage on 08/02/2018 04:18 amWith a radius of 28-48m they would be able to simulate Mars G or higher at low spin rates which should be well within the tolerances of the interstage docking clamps, and without any of the potential dynamic issues of nose-to-nose tethered connections.Has SpaceX given any specs on those clamps, and their use during propellant transfer? I hadn't seen, so I proposed a mod to the lines instead.
Edit: I've also remembered that keeping the landing propellant cool is going to be the main reason the BFS wants to stay pointed at the sun, and not engage in any spin G experiments. Having said that EM has mentioned the tankage for the landing prop could be subject to redesign.
Quote from: mikelepage on 08/03/2018 06:58 amEdit: I've also remembered that keeping the landing propellant cool is going to be the main reason the BFS wants to stay pointed at the sun, and not engage in any spin G experiments. Having said that EM has mentioned the tankage for the landing prop could be subject to redesign.Just leave the tanks as empty as possible and refuel once the spinning part of the flight has ended.
My assertion that it can probably take it, is based on the fact that prior to stage separation (if the falcon 9 flight profile is anything to go by), those clamps are stabilising some 1335 tons of BFS under 3x gees of compressive force.
Basically I find it hard to believe that clamps built to take 40 MegaNewton in compression wouldn't be able to take 1 MegaNewton in tension.
Edit: I've also remembered that keeping the landing propellant cool is going to be the main reason the BFS wants to stay pointed at the sun, and not engage in any spin G experiments.
Quote from: J-V on 08/03/2018 07:10 amQuote from: mikelepage on 08/03/2018 06:58 amEdit: I've also remembered that keeping the landing propellant cool is going to be the main reason the BFS wants to stay pointed at the sun, and not engage in any spin G experiments. Having said that EM has mentioned the tankage for the landing prop could be subject to redesign.Just leave the tanks as empty as possible and refuel once the spinning part of the flight has ended.Veering off topic now, but that's not actually an option. The only reason BFR can get away with so little landing fuel as it is, is that it goes directly into atmospheric entry from interplanetary velocities. There's nowhere to refuel from, between cruise phase and atmospheric entry.Therefore, spin gravity tests during interplanetary transits will only be possible if SpaceX decides to implement some kind of active cooling of its landing fuel, which is possible, but not currently planned.
I missed the part where the thread moved from space stations to Mars-Earth transits. Please carry on...
Quote from: mikelepage on 08/03/2018 06:58 amMy assertion that it can probably take it, is based on the fact that prior to stage separation (if the falcon 9 flight profile is anything to go by), those clamps are stabilising some 1335 tons of BFS under 3x gees of compressive force.Compression <> tension.Quote from: mikelepage on 08/03/2018 06:58 amBasically I find it hard to believe that clamps built to take 40 MegaNewton in compression wouldn't be able to take 1 MegaNewton in tension.Because you're assuming the clamps themselves (rather than rest-plates) are taking the entire force.
Quote from: mikelepage on 08/03/2018 06:58 amEdit: I've also remembered that keeping the landing propellant cool is going to be the main reason the BFS wants to stay pointed at the sun, and not engage in any spin G experiments.It's not hard to keep your spin-axis pointed at the sun, even when orbiting Earth. The hard part is the reflection from Earth. It's about a third the sun's direct heat, IIRC.
But, if you're in Earth orbit, then it's relatively simple to buy an orbital refuelling for the landing fuel. One tanker should be able to refuel all 4 of them with enough to land.My issue remains that it's a waste of BFSes. Musk wants to use them. Having four sitting around in a paddock full of rats (from his point of view) is a waste. He is going to charge you appropriately. I suspect somewhere around the replacement value over two years. And no mysterious funder is going to pay that.
Even if you were to spin that up to 1G (4.3 rpm at r=48m), the centre of mass of BFS at that stage is well down towards the engines (perhaps 16m or 1/3 of the radius away from the clamps), so the tensile force on the clamps would be on the order of 1.1 x 10^6N.
Quote from: Paul451 on 08/03/2018 09:41 amQuote from: mikelepage on 08/03/2018 06:58 amBasically I find it hard to believe that clamps built to take 40 MegaNewton in compression wouldn't be able to take 1 MegaNewton in tension.Because you're assuming the clamps themselves (rather than rest-plates) are taking the entire force.[...] Clamps that are able to resist 0.5-0.6xG force vibrations, laterally on a 1335 ton BFS during Max Q, I would have imagined would be capable of taking as much as 1xG in tension on a much lighter (~335 ton) BFS in a much more benign space environment.
Quote from: mikelepage on 08/03/2018 06:58 amBasically I find it hard to believe that clamps built to take 40 MegaNewton in compression wouldn't be able to take 1 MegaNewton in tension.Because you're assuming the clamps themselves (rather than rest-plates) are taking the entire force.
Quote from: Paul451 on 08/03/2018 09:41 amIt's not hard to keep your spin-axis pointed at the sun, even when orbiting Earth.Keeping your spin axis pointed at the sun doesn't necessarily shade the engines.
It's not hard to keep your spin-axis pointed at the sun, even when orbiting Earth.
If I was proposing spin G with BFS's to Musk, it would be to do this as an experiment whilst in transit to and from Mars
Fair call, compression is not the key factor, my mistake. ...Presumably the interstage clamps must be capable of this too, and I'm not sure whether building bigger rockets does anything to change this issue.Clamps that are able to resist 0.5-0.6xG force vibrations, laterally on a 1335 ton BFS during Max Q, I would have imagined would be capable of taking as much as 1xG in tension on a much lighter (~335 ton) BFS in a much more benign space environment.
I thought the point of keeping the BFS pointed at the sun was to keep the engine (and associated structures) shaded, as these are what will conduct heat into the landing prop tanks. Keeping your spin axis pointed at the sun doesn't necessarily shade the engines.
I tend to agree re in-orbit use of BFS's. If I was proposing spin G with BFS's to Musk, it would be to do this as an experiment whilst in transit to and from Mars, which he's said will include BFS's travelling in pairs. As long as you're not compromising the spacecraft in any way, this could be a minimum effort method of getting some partial G data, and increasing passenger comfort.