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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 fue

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 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 3y ago
Permalink: https://josh.vanderhook.info/publications.html#josr2022sspe https://josh.vanderhook.info/publications.html#josr2022sspe
spockz 3y ago
What is that saying? Never underestimate the bandwidth of a truck full of harddisks. I guess this is the solar equivalent.
- deleted 3y ago
  [deleted]
- tejtm 3y ago
  tapes (reels) in a stationwagon ... but you got the gist of it
  - actionfromafar 3y ago
    I think the Scriptures must be translated into the language of the People, to get with the times.
    - aftbit 3y ago
      Never underestimate the bandwidth of a Tesla full of SD cards.
markwkw 3y ago
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 3y ago
  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 3y ago
  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 3y ago
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 3y ago
  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.

jvanderbot 3y ago

Permalink: https://josh.vanderhook.info/publications.html#josr2022sspe https://josh.vanderhook.info/publications.html#josr2022sspe

spockz 3y ago

What is that saying? Never underestimate the bandwidth of a truck full of harddisks. I guess this is the solar equivalent.

deleted 3y ago
[deleted]
tejtm 3y ago
tapes (reels) in a stationwagon ... but you got the gist of it
- actionfromafar 3y ago
  I think the Scriptures must be translated into the language of the People, to get with the times.
  - aftbit 3y ago
    Never underestimate the bandwidth of a Tesla full of SD cards.

markwkw 3y ago

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 3y ago
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 3y ago
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 3y ago

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 3y ago
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.