Mars Cyclers
planetocracy.substack.com
planetocracy.substack.com
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.
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.
The consequence of this varies, but includes castles as you suggest.
Sort of an interplanetary Starlink.
* 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.
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.
Lets call it PlanetLink :-)
Cool, a built-in freight vs. passenger rail.
You still have to boost the freight into the orbit to meet the cycler station/shuttle and deboost at the other end - why bother.
Most freight, e.g. food, medicines, robots, requires some shielding. And some requires temperature or even pressure regulation.
"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!
It doesn't have to, because shipping to an Antarctic base is both quicker and much cheaper than shipping to Mars. Making it completely self-sufficient would require a substantial investment that's not really needed considering we have ships that regularly do the journey.
OTOH, NASA could be interested in doing exactly that, as air and water is all they can have for ISRU (unless they hunt for penguins and seals), and there is already a bunch of extremely clever people on-site that would probably be glad to be able to grow plants during their winter stays. Fresh fruit must be something highly coveted in that place.
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.)
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?
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.
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.
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.
Unless you think of it as a giant experiment to travel outside the Solar system, further down the road, when the Sun will eat up the entire solar system. In that case, though, you'll need a larger cycler with a much different shuttle for you to board/unboard it...
This is quite funny to think about. Seeing a trash laden ship blasting past would be quite the sight.
"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)."
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...
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.
Noted.... but it isn't. ;-)
You have it reversed. The truism you're looking for is: "Just because something is popular, doesn't mean it's correct." Don't let Likes and Followers culture fool you.
If you want to make your own SI, feel free to use it however you want. If you use the SI, you MUST (RFC 2119) follow the official SI brochure, otherwise you're objectively wrong. That's what standards mean, and they exist for many good reasons.
It's not your fault. This flavor of philosophical deterioration happens when you tell an entire generation to follow their heart, everybody's a winner, and there's no wrong just "different." This mental trap is hard to escape, and worse it impedes self-improvement.
In the field of linguistics it very much IS the case that what is popular is correct. Beginning a sentence with a conjunction, or ending a sentence with a preposition is perfectly fine in English for example, despite what many outdated grammar texts would tell you.
I don’t know if units like watt or newton are more frequently capitalized or not. It is common though. In which case it would not be wrong to do so in a blog post. (For a submitted article you’d use whatever the editorial standard is though.)
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.
* 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.
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.
My argument stands though, just extended to SubStack.
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.
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.
https://en.wikipedia.org/wiki/Io_(moon) "the lowest amount of water (by atomic ratio) of any known astronomical object in the Solar System"
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.
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.
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.
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
The mass a rocket can lift into space is inversely proportional to the mass of the propellant. To increase the payload (a larger cycler like the previous poster mentioned), you need to increase the initial total mass of the rocket, which includes the mass of the propellant.
So it's not linear, it's exponential, the "tyranny" of the rocket equation.
Or are you talking about a completely different equation?
This one, which is the only one I know of to get this moniker, is about mass fraction, not absolute mass. You can perfectly compensate for making m_f bigger by making m_0 bigger by exactly the same ratio, hence for fixed Δv, m_0 increases linearly with m_f.
Two rockets joined horizontally has twice the mass of one rocket alone, and accelerates twice as much payload to the same relative velocity as a single rocket.
Two rockets joined end-to-end, with the second rocket being the payload for the first, makes the ultimate payload of the second stage go faster than if it had only been propelled by the second stage with no boost from the first, but significantly less than twice as much faster.
You can also see this example by asking the inverse: if it was exponential with regards to absolute payload rather than the payload as a mass fraction, that would mean that dividing any given payload into two or more parts, launching them separately to the same ultimate velocity, and having them join together in space, would save fuel — it doesn't, QED.
(There are other reasons to build in space, like "our rockets aren't big enough and nobody wants us to build bigger ones", but that's a political equation, not rocket science).