[HN Gopher] Mars Cyclers
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Mars Cyclers
Author : rbanffy
Score : 59 points
Date : 2023-10-31 15:38 UTC (7 hours ago)
(HTM) web link (planetocracy.substack.com)
(TXT) w3m dump (planetocracy.substack.com)
| micromacrofoot wrote:
| I hope getting humans to Mars can inspire more investment in
| space travel and exploration, or even another space race... but
| I'm not sure that it will happen. Putting 1000 people on a ship
| seems like a pipe-dream adjacent to full-self driving at this
| point.
|
| At the moment all of this feels like a mistake... for the cost of
| a manned program we could be sending out dozens of probes and
| rovers, not only to Mars but to more interesting places like
| Jupiters moons, Io and Europa, the former being the most
| volcanically active body in the solar system, and the latter one
| of the most promising places to find liquid water.
| photochemsyn wrote:
| People and governments make all kinds of mistakes, and when
| comparing manned to unmanned space programs and their relative
| costs, it's worth examining what the overall societal
| expenditures look like.
|
| For example, the cost of maintaining the USA's nuclear arsenal
| is very comparable on a yearly basis to the entire NASA budget
| (~25-30 billion). However this pales in comparison to the
| complete amortized cost of the US adventure in Iraq from
| 2003-2008 or so, which is on the order of $2.5 trillion (large
| error bars there), or about $500 billion per year.
|
| Conclusion: we certainly have the civilizational resources to
| increase both unmanned and manned space programs by at least
| 15-fold each if we'd just stop wasting money on stupid wars.
| Note that's just USA expenditures, as well.
| ceejayoz wrote:
| Liquid water? On Io?
|
| https://en.wikipedia.org/wiki/Io_(moon) "the lowest amount of
| water (by atomic ratio) of any known astronomical object in the
| Solar System"
| micromacrofoot wrote:
| My mistake, Io is volcanically active with a possible ocean
| of magma, Europa has the possible subsurface liquid ocean.
| Edited to reflect this.
| distortionfield wrote:
| > Putting 1000 people on a ship seems like a pipe-dream
| adjacent to full-self driving at this point.
|
| we have centuries of experience with doing the exact same thing
| to people at sea.
|
| > for the cost of a manned program we could be sending out
| dozens of probes and rovers
|
| Why not both? I see the value in each.
| micromacrofoot wrote:
| Eventually yes, but it seems we're putting the cart before
| the horse.
|
| I really hope it goes well and we end up accelerating things
| with another space race, this is the best outcome and maybe
| this is why we're shooting for manned Mars missions... but
| it's risky. A crew of dead astronauts on Mars could have the
| opposite effect. Imagine if Nixon really had to deliver that
| failure message about the moon landing, space exploration
| could be even worse off than it is now.
| kjs3 wrote:
| I think sending a person across the ocean, under an
| atmosphere, protected from radiation, with gravity isn't "the
| exact same" thing as through space. Much less 1000.
| Pretending that it is...charitably...is silly.
| PaulDavisThe1st wrote:
| True, but this works in reverse too.
|
| Much harder to get the initial, small scale version of a
| cycler-based transit system established. But then,
| _because_ you don 't have an atmosphere or ocean or
| particularly noticeable gravity, scaling it up it probably
| much, much easier than doing so for ocean-going vessels and
| the like.
| kjs3 wrote:
| Maybe? My point is if you are going to do it, start with
| a mental model that fits the task, not one that both
| isn't remotely the same engineering challenge and ignores
| the actual hard problems.
| PaulDavisThe1st wrote:
| Well, we're a good part of the way towards being able to
| move people from the earth's surface into orbit.
| Somewhere between, say, 20% and 80%. If that claim is
| true, then it seems reasonable to be thinking about what
| comes next, and building a _small_ cycler seems like a
| potentially reasonable choice.
|
| If we can indeed build a small cycler, then getting to a
| big one may be much easier than going from a small yacht
| to a transoceanic liner.
| accrual wrote:
| > If we can indeed build a small cycler, then getting to
| a big one may be much easier than going from a small
| yacht to a transoceanic liner.
|
| It still falls apart a bit due to the rocket equation.
| [0] When you're in a safe harbor on earth, it's somewhat
| simple to increase the size of your boat, most of the
| rules stay the same.
|
| But as you build bigger cyclers, one will either need
| bigger rockets or more rockets and then possibly
| assembly/docking in space, so it's definitely more
| complicated than making a larger displacement in the
| water.
|
| [0]
| https://en.wikipedia.org/wiki/Tsiolkovsky_rocket_equation
| geuis wrote:
| I really wish people would stop using Medium. A problem I've been
| running into over the last few months is that an increasing
| number of potentially informative articles are hidden behind a
| Medium sign-in wall.
|
| * Edit
|
| As commenters mentioned this is on substack. My apologies.
|
| I still stand by my original statement though. The sign-in walls
| are a problem.
|
| Ironically when I go back to visit the substack link on the
| parent, there's no longer a sign in requirement.
| LeifCarrotson wrote:
| Do you see the "Continue reading" grey text? It's clickable and
| lets you get past the sign-in wall. You don't have type your
| email, subscribe, or log in.
|
| I usually close out of any sites that bring up such an
| attention-stealing popup out of principle, but I've found
| enough insightful content on Medium that I'm willing to ignore
| this dark pattern.
| wffurr wrote:
| This isn't on Medium; it's on Substack. There's a "please sign
| up" nag dialog with a "Continue Reading" link. There's no wall.
| geuis wrote:
| Whoops totally right. My mistake.
|
| My argument stands though, just extended to SubStack.
| InitialLastName wrote:
| Your argument doesn't stand. I'm sure it's possible to
| paywall articles on those websites, but in every case I've
| seen the subscribe wall is dismissable with a single click.
| Annoying, yes, but more of a gate than a wall.
| Teever wrote:
| I really wish people would talk about space stuff in a post
| about space stuff and not medium or substance stuff.
| JumpCrisscross wrote:
| "Mars trajectories can be closer to 4 km/s during the right part
| of a favourable window, but they can take a year to arrive"
|
| Cool, a built-in freight vs. passenger rail.
| robocat wrote:
| Bulk freight mostly doesn't need radiation shielding or life
| support services, so what would be the advantage to using a
| cycler station/shuttle for freight?.
|
| You still have to boost the freight into the orbit to meet the
| cycler station/shuttle and deboost at the other end - why
| bother.
| JumpCrisscross wrote:
| > _Bulk freight mostly doesn 't need radiation shielding or
| life support services_
|
| Most freight, _e.g._ food, medicines, robots, requires _some_
| shielding. And some requires temperature or even pressure
| regulation.
| lostlogin wrote:
| > Current space stations use their discarded cargo vessels to get
| rid of waste that cannot be recycled, leaving it to burn up in
| the Earth's atmosphere. What a cycler could do is package it in
| some way that it could be fixed to the outside of the station.
|
| This is quite funny to think about. Seeing a trash laden ship
| blasting past would be quite the sight.
| jvanderbot wrote:
| Cycler orbits are cool, but slightly over-constrained. You can
| pass close to Earth and Mars on a more interesting cadence if
| you're willing to burn a little fuel to adjust the cycler once in
| a while. The "perfect" cycle orbit ala Aldrin Cycler is just one
| special, theoretically-stable case.
|
| So, Starship on a cycler-like orbit is _really much more powerful
| than discussed here_.
|
| I once wrote a few articles about using custom-made cycler
| trajectories to ferry _data_ back and forth.
|
| * You don't have to accelerate data up to speed, just beam it to
| the "ferry" when it's close to Mars, and beam it to earth when
| you're close to Earth
|
| * You can get _enormous_ amounts of data back this way, b/c you
| can use very high data rates when transmitter and receiver are
| close
|
| * For example, you can map the entire surface of Mars in high
| resolution quite frequently, if you are willing to wait a bit to
| get that data back
|
| * And you can still downlink data normally 364 days a year - with
| one day scheduled for a Petabit scale transfer to the data
| "ferry"
|
| This PDF is open access:
| https://arc.aiaa.org/doi/10.2514/1.A35091
|
| And if you scroll through, there's some examples of "ugly"
| cyclers, which have a more interesting cadence and require a
| little bit of fuel to maintain.
|
| By batching ugly cyclers, you can get multiple flybies, and not
| just constrained to the synodic cycles of the two planets. For
| example there's a 1-2 /year flyby schedule.
| jvanderbot wrote:
| Permalink:
| https://josh.vanderhook.info/publications.html#josr2022sspe
| spockz wrote:
| What is that saying? Never underestimate the bandwidth of a
| truck full of harddisks. I guess this is the solar equivalent.
| tejtm wrote:
| tapes (reels) in a stationwagon ... but you got the gist of
| it
| actionfromafar wrote:
| I think the Scriptures must be translated into the language
| of the People, to get with the times.
| aftbit wrote:
| Never underestimate the bandwidth of a Tesla full of SD
| cards.
| markwkw wrote:
| Isn't the utility of the cycler that it can be a massive object
| with a lot of shielding for humans and permanently installed
| life support systems? Like a big space station for whole crews
| to live safely and comfortably while in transit.
|
| You (incrementally) build up a large cycler in parts, each part
| accelerated to the orbit once.
|
| Once the cycler is large, it seems infeasible to burn fuel to
| periodically adjust the orbit since it's massive. Unless
| propellant less stuff like light sails can be used over long
| periods.
| jvanderbot wrote:
| The benefit of a cycler is the near zero delta V required to
| maintain it, and the fact that it flies by two interesting
| orbits, like Mars and Earth.
|
| The consequence of this varies, but includes castles as you
| suggest.
| adastra22 wrote:
| Yes, it could be essentially a cruise ship for the journey,
| and starships are used just to ferry passengers and supplies
| to/from the cycler at each destination. With life support
| closure you might not even need much in supplies.
| ragebol wrote:
| I wonder if it's possible (and sensible) to have a bunch of
| cyclers after each other, spaced eg a month apart. The distance
| between them would be much shorter than Earth -Mars and thus
| allow much faster data transfer. With these cyclers as relays,
| there's always one close to Mars, another close to Earth.
|
| Sort of an interplanetary Starlink.
| jvanderbot wrote:
| We did look at that. In fact it's quite possible to have a
| "train" like this, but:
|
| * Continuous relay is power-hungry, and the distances are
| still huge unless you have a _lot_ of relays on _very_
| different heliocentric orbits. The scale of the inner solar
| system is _enormous_ compared to LEO. High power on lots of
| satellites means huge cost on a per-unit basis. LEO is 100km
| away vs 1/5 distance to Mars is still 80 million km or so.
| Transmission power for a given rate is d^2 (or d^3 in some
| cases for lasers). Enormous power requirements.
|
| * On earth, you can "space out" an orbit so that you
| basically always have either another satellite on the same
| orbit, or a "nearby" orbit that has one coming up. Look at
| GPS tracks, for example. In inner solar system, everything
| orbits the _sun_, meaning nearby orbits might be nowhere near
| earth, and even a train on the same orbit is going to miss
| Earth 99.9% of the time by a million km or more.
|
| * An interplanetary relay has been studied. Instead of
| cyclers which pass close, you basically put a "train" of
| spacecraft on a heliocentric orbit between earth and mars.
| Again, this was a _lot_ of spacecraft required to get relays
| such that the cost paid off relative to just building bigger
| transmitters / listeners on earth or having more orbiters
| around Mars.
|
| The sweet spot of cyclers is low thrust requirements,
| comparatively low system requirements (big burst of data once
| in a while with lots of charging between), which combined to
| make sats small enough to justify a dozen or so on a single
| launch of this purpose.
|
| I _do_ think we'll have solar-system-starlink. Probably at
| Mars, definitely at Moon, and likely some lagrange point
| relays with a cycler or two funded by an eccentric billionare
| in 50 years.
|
| EDIT: I misunderstood, below is old comment / reply
|
| That is precisely the subject of the paper I linked. Except
| you can't confuse visit frequency with visit _latency_. We
| can have many visits per year but all the data coming down is
| usually over a year old. For Grand Science on a planetary
| scale this is ok. And for lower latency data requirements (of
| which there are not really many cases outside human
| impatience) you can use regular downlink but only .01% of the
| throughput.
|
| But it gets even more interesting if the data "ferry" has
| enough compute to work while moving. You could run models on
| the ferry to answer questions, then every so often (when
| close to earth) download all the data to verify answers.
|
| What we derive and optimize is the orbits to achieve such a
| "high frequency" cadence by formulating a set cover instance.
|
| The sets are the visits for each cycler and we want to
| "cover" a given time span with "enough" visits.
|
| And the cyclers themselves are a large parameter sweep
| conducted somewhat open loop.
| nwiswell wrote:
| > That is precisely the subject of the paper I linked.
|
| GP was actually proposing inter-cycler links to create a
| kind of cycler network with Earth on one end and Mars on
| the other.
|
| That is, your latency comes from the speed of light, rather
| than the inter-cycler latency.
| ragebol wrote:
| Exactly. Have some sort of chain of cyclers that each
| cycle independently, launched/spaced (hehe) eg. a month
| apart. As they cycle, only one of them will be closest to
| Mars, that gets the uplink from Mars, then relay the data
| to the cycler behind it, that relays to the one behind
| etc etc until we reach the cycler that is closest to
| Earth, in mere minutes. Can have laser links between them
| even maybe.
|
| Lets call it PlanetLink :-)
| jvanderbot wrote:
| Good catch, thanks. I updated my reply. it's a good idea
| that has some backing in literature and I do think we'll
| see it soon enough.
| tempodox wrote:
| There ought to be a space between a number and its unit.
| "500mSv/yr" --> "500 mSv/yr". Neglecting this is a really bad
| habit.
| schiffern wrote:
| If you think that's bad, check out the (also terribly sourced)
| citation they linked for Apollo's exposure of 20 mSv through
| the Van Allen belts[0]: "The actual amount of
| radiation received by the Apollo astronauts during their
| passage through the van Allen belts is difficult to determine
| but it is estimated to be about 2 rems (or 20 milli-Sieverts)."
|
| A _hyphen_ between prefix and unit? _Capitalizing_ a unit that
| 's named after a person? It's an absolute mess.
|
| It seems almost nobody is aware of the (official/authoritative)
| SI brochure[1] anymore, or even its poor cousin, Wikipedia's
| Manual of Style for Units of Measurement[2].
|
| [0] http://apolloarchive.com/apollo/moon_hoax_FAQ.html
|
| [1] https://www.bipm.org/documents/20126/41483022/SI-
| Brochure-9-...
|
| [2]
| https://en.wikipedia.org/wiki/Wikipedia:Manual_of_Style_(dat...
| adastra22 wrote:
| Like Watts?
| schiffern wrote:
| Yes, "Watt" and "Newton" are surely the most common
| culprits.
|
| When speaking of them as people, they are of course
| capitalized.
|
| When speaking of them as units, they are _not_ capitalized
| (1 watt). However the abbreviation _is_ capitalized (1 W),
| and I think this is mainly what confuses people.
| marcosdumay wrote:
| Personally, I really don't like this rule.
|
| It's made for another typographic environment, with
| restrictions that do not apply the same way today. And adds
| semantic noise to the text.
|
| The Unicode people could make a different kind of space for use
| there, but I don't think anybody would adopt it. It looks like
| something that should be handled by a mechanism similar to
| ligatures.
| adastra22 wrote:
| You would use a non-breaking space.
| skywhopper wrote:
| Not sure what this really gets you, since you still need to
| change your velocity in the exact same amount on both ends of the
| trip. The Cycler can get you there in four months vs a year...
| but you need to use just as much fuel on both ends of the trip as
| you would to make it in four months.
|
| It seems the idea is that you could pack people in for the few-
| hour journey to the Cycler, and the departing journey once you
| get to Mars, and give them more space and shielding during the
| voyage. But that all requires that a large, spacious, well-
| shielded Cycler is already in place. This is all covered in the
| article, but just as an interesting aside rather than a massive
| impediment to the utility of such a piece of infrastructure.
|
| All of this is such a distant problem, it seems way too soon to
| even speculate on. We're hundreds of years away from the
| logistics of transporting thousands of humans to Mars being a
| practical consideration. As such, the mere mention of Starship
| feels utterly anachronistic. Even if you think colonizing Mars is
| a good idea, wasting time thinking about problems for the year
| 2300 is not the best use of your time.
|
| (The article is from 2021 by the way.)
| marcusverus wrote:
| > We're hundreds of years away from the logistics of
| transporting thousands of humans to Mars being a practical
| consideration.
|
| With decades of experience with the ISS and Starship's first
| orbital flight on the docket, why would this be hundreds of
| years away? Consider the technical progress we've made in
| launch vehicles in the last 15 years alone. Are there really
| any technical problems on the path to a mars cycler that could
| give us centuries worth of trouble? Or are you simply
| suggesting that the demand won't be there?
| phkahler wrote:
| >> All of this is such a distant problem, it seems way too soon
| to even speculate on. We're hundreds of years away from the
| logistics of transporting thousands of humans to Mars being a
| practical consideration. As such, the mere mention of Starship
| feels utterly anachronistic.
|
| This is not hundreds of years away, it is the goal of SpaceX.
| They are not just building Starship, they are building a
| factory with a target production rate of one ship per day. The
| goal is not to send a few ships to Mars, but an armada. With so
| many ships around, and a window to Mars about every 2 years it
| makes sense to start building infrastructure like this with
| them while they're waiting.
|
| Yes, Elon is a bit... ambitious. And I question whether he is
| actually serious about it all. But if he is, this is happening
| over the next 50 years.
| giantrobot wrote:
| > They are not just building Starship, they are building a
| factory with a target production rate of one ship per day.
|
| So SpaceX is going to build a Starship, which has to travel
| tens of millions of miles through the unforgiving frontier
| that is space, at one a day? Boeing manages to build a 737 in
| about nine days and those land on Earth every few hours of
| operation for maintenance and checkups.
| bacheaul wrote:
| Those two vehicles have very different flight profiles, so
| comparing them is of limited value, but yes, that is the
| plan.
| schiffern wrote:
| >you still need to change your velocity in the exact same
| amount on both ends of the trip
|
| You usually need to change your velocity _more than that_.
|
| Cycler orbits are more constrained in their start/end dates, so
| there are fewer free parameters to "tune" for lower propellant
| consumption. Generally a cycler with a 4 month transit time
| will need slightly more delta-v vs. sending a ship on a regular
| old transfer orbit with an identical 4 month transit time.
|
| This is because when designing a cycler orbit it's usually
| necessary to shift a few days ahead/behind the optimum dates
| for a 4 month transfer, in order to efficiently "stitch
| together" with the previous/next orbit cycle.
| mrlonglong wrote:
| Exactly as described in Buzz Aldrin's book Encounter with Tiber.
| Very very good yarn about humanity's effort to walk between the
| stars using knowledge left behind by visitors, culminating with
| the first human to set foot on a non human world.
| Animats wrote:
| It's kind of like an updated version of the Colliers' Space
| Program. Huge infrastructure in orbit.[1]
|
| _" No budget is included for cargo to support passengers on
| Mars, as it is assumed by the time this is done there will be a
| well functioning city at the other end to support them."_
|
| That's likely to be a big problem. Most of the mass shipped will
| probably be cargo. Think in terms of an Antarctic base. Doesn't
| produce anything, totally reliant on external supply.
|
| [1] https://en.wikipedia.org/wiki/Man_Will_Conquer_Space_Soon!
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