Aldrin Cyclers and Asteroid Belt Cyclers

tahanson43206 · 2019-09-08 18:13:22

For GW Johnson re #20 ...

Thank you for considering the solid rocket option for a vehicle for docking at Phobos after departure from a Cycler.

I thought of a solid rocket as a reasonable option because it would (presumably) not deteriorate during flight from Earth to Mars. Solid rockets are used for US land based missiles, and for submarine based missiles, and my understanding (from generic news and nothing further) is that these designs sit in launch silos for months or years without deterioration.

Your post about the manufacture of solid fuel rockets was helpful, in the sense that it provides a glimpse of the complexity of manufacture of these devices.

A solid rocket would need to be ignited at the right time to deliver the personnel capsule to the docking station with minimal cold thruster adjustments.

I would envision all passenger pods disconnecting from the Cycler well ahead of the moment when ignition is required, and coasting to the point where ignition occurs under computer control. A situation that might arise is that the solid rocket fails to ignite. In that case, the pod could simply return to the Cycler using cold gas thrusters. The passenger would get to ride around the full circuit back to Earth, which might be a bummer but at least they would be there to make the trip.

I would expect that transfer of passengers and cargo to the Cycler from Phobos (or a comparable Earth LEO station) would be accomplished with a larger, multiple passenger vehicle, although it might prove cost effective to keep the single passenger option in reserve for special situations.

(th)

Last edited by tahanson43206 (2019-09-08 18:16:36)

RobertDyck · 2019-09-08 18:14:56

You guys are talking advanced propulsion concepts? One study by NASA was something called "micro-fusion thruster". I'm sure it isn't a coincidence that maneuvering thrusters by the Star Trek TNG ship, Galaxy class Enterprise D, were supposedly called that. But the NASA study proposed a "basket" structure that produced a dish shaped magnetic field. Into that field fired a pulse of multiple magneto-plasma dynamic thrusters (MPD). MPD thrusters were actually developed by the Glenn Research Centre, they've been tested in the lab and work. GRC optimized Isp by using hydrogen propellant. But this new idea was to use a bunch of them to fire a mix of deuterium and tritium so the pulse from each would focus on a point in space in the centre of the magnetic "basket", igniting a fusion pulse. The fusion pulse would be repelled by the magnetic field, exhaust aft and thrust forward. Theoretical study, nothing built. Do you want me to find the paper? It was by NASA's advanced concepts department.

kbd512 · 2019-09-08 19:02:55

Robert,

Yes, I'd like to see that paper. I wasn't aware of that until you posted about it.

tahanson43206 · 2019-09-08 19:37:35

For RobertDyck ...

Your description of the Glenn Research Centre idea to ignite deuterium and tritium reminded me of the Lawrence Livermore Labs study of laser beams trying to do the same thing. The GRC sounds a LOT more practical for a space vehicle. But the similarity of the objective is what brought the Ignition Facility work to mind.

For kbd512 ... I too would definitely be interested in the GRC paper!

https://lasers.llnl.gov/

The Lawrence Livermore labs ignition facility just celebrated 10 years of operation.

https://www.sciencemag.org/news/2016/06 … -concludes

Giant U.S. fusion laser might never achieve goal, report concludes
By Daniel CleryJun. 21, 2016 , 9:30 AM
A long-troubled laser megaproject is facing fresh hurdles.
A recent report concludes that although the $3.5 billion National Ignition Facility (NIF)—a Department of Energy (DOE) laser lab designed to heat and compress capsules of hydrogen isotopes until they fuse, releasing energy—is making technical progress, it is still a long way from its titular goal: ignition, or a fusion burn that sustains itself and produces more energy than it takes to spark it.
According to Physics Today magazine, the independent report, sponsored by DOE, suggests NIF-related research should shift from identifying the obstacles in the path to ignition, to whether ignition is even possible.

It's been a while since I checked in on this effort, so I was surprised to read this pessimistic appraisal.

GW Johnson's advocacy of using small fission devices for large vehicle propulsion is looking better (to me at least) at this point.

****

One other concept I'd like to toss into the mix (regarding propulsion of a large vessel in the Earth/Mars circuit) is the availability of a constant stream of particles in the Solar System. As I recall the Bussard fusion rocket concept, a large scoop was extended from the vessel to collect hydrogen from free space for use as reaction mass. The harvest of particles in the Earth/Mars region should be much greater than would be found in intergalactic space. Whether collecting the particles would be worth the effort is a question, but it seems worth noting that the opportunity is there.

Google came up with a list of citations when I asked: "bussard ramjet"

(th)

Last edited by tahanson43206 (2019-09-08 19:50:54)

RobertDyck · 2019-09-08 20:26:19

Engineering of the Magnetized Target Fusion Propulsion System

G. Statham, S. White, R.B. Adams, Y.C.F. Thio, J. Santarius, R. Alexander, S. Fincher, T. Polsgrove, J. Chapman and A. Philips
NASA Marshall Space Flight Center, Advanced Concepts Department, Huntsville, AL 35812, USA.
ERC Inc., 555 Sparkman Drive, Executive Plaza, Suite 1622, Huntsville, AL 35816, USA.
US. Department of Energy, Ofice of Fusion Energy Sciences, 19901 Germantown Road, Germantown, MD 20874, USA.
Institute of Fusion Technology, University of Wisconsin, Madison, WI 20874, USA.
Abstract. Engineering details are presented for a magnetized target fusion (MTF) propulsion system designed to support crewed missions to the outer solar system. Structural, thermal and radiation-management design details are presented. Propellant storage and supply options are also discussed and a propulsion system mass estimate is given.

Note: MPD was developed at Glenn Research Centre. This paper was sponsored by the Advanced Concepts department.

SpaceNut · 2019-09-08 20:29:06

Deuterium and Tritium fusion means a containment field for the forcing of the energy out the nozzle of the drive engine. D-T fusion being radioactively benign is a myth as the reaction produces high energy neutrons that activate the materials that compose the reactor, forcing components, especially the inner wall, to need frequent replacement. This is simular to using he3 as well with hydrogen to get the same reaction to occur in a controlled chamber. D-He He-3 reactions produce no high energy neutrons, and consequently the activation of metals is drastically reduced. (Stray D D-D reactions will generate some neutrons).

The most promising of the hydrogen fusion reactions which make up the deuterium cycle is the fusion of deuterium and tritium. The reaction yields 17.6 MeV of energy but to achieve fusion one must penetrate the coulomb barrier with the aid of tunneling, requiring very high temperatures .

Helium-3 is a light, non-radioactive isotope of helium with two protons and one neutron. New experiments with helium-3 in a magnetic confinement tokamak have produced exciting results for the future of fusion energy.
https://www.lpi.usra.edu/decadal/leag/D … elium3.pdf
https://ocw.mit.edu/courses/nuclear-eng … fusion.pdf

tahanson43206 · 2019-09-09 20:11:53

For SpaceNut and others who may wish to continue discussion of nuclear fission propulsion ...

As manager of this topic, I am favorably inclined toward discussion of nuclear fission propulsion methods, including the nuclear pusher concept.

Due to the size of the Aldrin Cycler (as I am imagining it), a powerful and extremely reliable propulsion method is essential to keep the vessel moving safely in its circuit around the Sun, passing Earth and Mars on a planned schedule.

Gravitational perturbation of the orbit by planets, the Sun itself, and potentially other masses to a lesser degree, must be anticipated and dealt with.

(th)

SpaceNut · 2019-09-09 22:18:25

reposting as it fits here as well

SpaceNut wrote:

So what does a colonial sized ship need for atributes?
Plenty of supplies for all crew and then some.
Some methods for recycling so we are not needing gross amounts of anything burdening the mass of the ship futher making the means to move it slide up the nuclear power required scale.
Ag, radiation protection and work that can be carried on in the passage of time from place to place.
Cere would be a good loop destination as its got water but you only have a short time for the crew to exit, mining and then return to the ship as it comes back by.

As for power from nuclear sources solar sort of gets marginal once we are in the mars local area and beyound so its something that must be working for a large ship to do what we want to go do.

tahanson43206 · 2019-09-10 08:10:30

For SpaceNut re #33

Thank you for this substantial boost to the Aldrin Cyclers topic (of 2019)!

I like the idea of collecting supplies for the vessel while passing through the asteroid belt, and would like to add to it by pointing out that a mining operation should be robotic. The supplies can be collected and purified during the long periods between visits by the Cycler.

For GW Johnson .... I am picking up on your interaction with the Naval Academy, which you commented upon recently here, and at greater length in your blog.

The vessel I have in mind for this topic is aircraft carrier sized, and nuclear powered. The vessel would have a large crew, and an officer cadre of stature.

I am aware of at least one very forward looking paper written by Annapolis students a few years ago, to evaluate one of the many options for high speed interstellar travel. It would not surprise me at all to learn that such studies are routine for Academy students.

In the context of this topic, I am looking forward to a time when young people alive on Earth today will be successful enough in business to be able to fund one or more cyclers, plus the orbiting stations at Earth and Mars. Those entrepreneurs will need to hire officers and crew for the cyclers, in addition to all of the Architects and Engineers to head up the construction effort. Thus, I am wondering if there may be someone at Academy today who would be interested in bending his or her studies to include an option to lead the Cycler development effort, and ultimately to take command of one of the vessels.

Finally ... for anyone .... Elon Musk launched Starman as a demonstration of the capabilities of the Falcon Heavy. The vehicle is in an orbit that reaches nearly to the orbit of Mars (details are available online) and which returns to Earth's orbit. The Starman vehicle recenly completed its first full orbit, according to a note I saw on the Internet recently. The Starman vehicle could be adapted for service as an Aldrin Cycler prototype, although the plane of the orbit is unlikely to match the original concept.

Is there anyone in the forum who would be able to compare the existing Starman orbit to the Aldrin Cycler concept?

Thanks!
(th)

SpaceNut · 2019-09-10 17:16:38

https://en.wikipedia.org/wiki/Elon_Musk's_Tesla_Roadster

Starman is in an elliptical orbit around the sun, with an estimated top speed of 7 miles per second. According to data from Where is Roadster, the cosmic driver has completed his first orbit around the Sun, taking 557 days since the first Falcon Heavy launch to circle our home star. Its path has taken it over 762 million miles since then, or enough to exceed its original 36,000-mile warranty over 21,000 times. It will be near Earth again on November 5th, 2020, when it'll be about 0.346AU (just under 32.2 million miles) away. https://theskylive.com/roadster-tracker

Animation of SpaceX Roadster's trajectory.

SpaceNut · 2023-08-13 14:45:48

Futuristic Paper Shows It’s Feasible to Build a Space Station on an Asteroid

Calliban · 2024-06-09 06:10:39

This small asteroid has an insane orbit.
https://en.m.wikipedia.org/wiki/1999_XS35

Its perogee is <1AU, whilst its apogee takes it beyond Neptune's orbit. I don't think cyclers are useful for orbits that are as wide as the outer planets. But this is scientifically interesting none the less. With such an elliptical orbit, this body is travelling at an insane velocity at perogee. If it ever did hit Earth, the results would be disasterous.

tahanson43206 · 2024-06-09 06:48:56

For Calliban re #37

Thanks for bringing this asteroid into view !!!

As an observation ... while matching orbits might be on the challenging side, this object could be a useful site for a scientific package of instruments to survey the Solar System from a perspective that would be difficult to acquire otherwise.

It might be possible to match orbits by doing some fly-by maneuvers.

The science package needs to be powered by a nuclear device (RTG) for the cold part of the orbit, but it might be able to use solar power inside of Mars' orbit.

(th)

Calliban · 2024-06-09 11:14:34

In years to come, man will have mapped the orbits of a large fraction of KBOs. If we discover that this asteroid makes a close approach to a body that we are interested in colonising, then it may be useful to hitch a ride. It would take a great deal of propulsive effort to match velocity with the asteroid, but no more than would be required to fly a ship directly to the orbit of Neptune. By matching orbit with the asteroid, a group of humans would get free water, air, cosmic ray shielding and raw materials, for the duration of the trip. It therefore reduces the mass that they need to take with them.

Pluto has an orbital speed of 4.7km/s. We can assume that to be typical of KBOs with similar semi major axis.
https://en.m.wikipedia.org/wiki/Pluto

The dV needed to match orbits with a KBO once out that far is therefore modest. Whatever propulsion system the colonists used to match orbit with the cycler asteroid in the inner solar system, could shift the velocity of two orders of magnitude more mass to a KBO matching orbit at their final destination. In the decades between intercepting the asteroid and leaving it, the colonists could manufacture much of what they need establish a colony at the KBO.

We can think of this asteroid as a springboard for a new KBO colony. The time between jumping on and jumping off will be about 40 years. We can build a lot of useful things in that time. One thing that we would need to take with us that we probably won't find enough of at our destination, is fissionable fuel. Each tonne of fissionable fuel yields about 3GW-years of harvestable energy. So 100 tonnes of uranium or thorium, a cube 1.7m (5.7') aside, would be enough to supply a colony of 1 million people for a century. That is more than enough time to get a fusion reactor set up.

Last edited by Calliban (2024-06-09 11:33:04)

SpaceNut · 2024-06-09 13:43:01

It would be nice, but I think that a Venus to the asteroid belt is a practical. With lots of them so as to have a cross-loop transport capability.

Calliban · 2024-10-09 07:06:38

This body is on an ideal orbit for an Earth-Mars cycler.
https://en.m.wikipedia.org/wiki/25143_Itokawa

It grazes both orbits and also has a low inclination. At least some hydration was detected in samples returned by the Japanese probe. Turning this body into a kind of long-stay hotel would make human settlement of Mars somewhat easier.

The problem with using a third body as a cycler is that after getting on it may take many orbits and many years, before there is a convenient close pass of the destination planet. You get to cross the gulf of space in comfortable, spacious and radiation shielded conditions. But you may be be stuck in that hotel for a long time before checking out. The cycler needs to achieve efficient recycling of effluents in a closed life support system. So really we have to colonise the cycler before we can colonise the place it is going to. This isn't so bad for people that really aren't interested in returning to Earth and ok with spending several years getting to where they want to go.

One way around long waiting times would be to establish several cyclers and to transfer passengers between cyclers using small taxi vehicles, as well as between cyclers and planets. By doing that, we can cut transit times to as little as a couple of years in either direction. I suppose if we are serious about colonising Mars we ultimately need to cough up the cash and invest in transport infrastructure. Not all of the cyclers need to be made out of asteroids on exactly the right orbit. It just saves propellant in setting it up if we can find a useful mass of material already on the right orbit. Itokawa could be the first of many cyclers. The more we build, the more useful the concept becomes in helping us to get where we are going. This suggests to me that colonisation of HEO, the Moon, near earth asteroids and Mars, will be simultaneous efforts with each benefiting the other.

An Earth-Moon/HEO cycler is a good idea. Although the moon is relatively close, it would be beneficial if people could make the journey in a spacious and shielded environment. The cycler itself would likely be a destination for space tourists. They would enjoy regular close approaches to Earth and the Moon. The Earth-cycler and cycler-HEO transfer taxis can be small lightweight vehicles with a high volume density of human bodies.

Last edited by Calliban (2024-10-09 07:58:49)

GW Johnson · 2024-10-09 14:59:23

Itokawa as a Cycler?

I have not computed the orbital ellipses, and investigated the crossings with Earth’s orbit and Mars’s orbit. But multiple big questions come to mind. The first is: how could Itokawa (or any other object) function as a “cycler”, when the differing orbital periods of 3 (not 2) bodies are involved? (That is actually a fundamental question that I have about all cycler proposals.) Bear in mind that unless the cycler is very close to the departure planet at one end, and the arrival planet at the other, there is little point in trying to effect the transfer via a cycler. Failing that proximity at both ends, you are better off just flying direct to your destination, in terms of both velocity requirements and time spent in space.

With further regard to that first big question, while there will be a repeating point in time (two of them actually) where the asteroid is at minimum distance from Earth, when it crosses Mars’s orbit (and there would be two opportunities for that as well) it would seem unlikely in the extreme (!!!) that Mars would be located anywhere near the correct vicinity for an effective transfer of anything. However, at least the plane of Itokawa’s orbit is close to the ecliptic, so crude coplanar estimates would be reasonably close. The cycler would have to have exactly the right period in order to line up with Earth while Earth is there, and to line up with Mars while Mars is there. The periods pf Earth and Mars are what they are. The period of the cycler is your only variable available by which to address the double-line-up.

I know very little about Aldrin’s cycler concept. But whatever period it has is the period any other cycler absolutely must have. I do not know how to figure that, but maybe Aldrin did. Whatever perihelion and apohelion distances go with that period, that’s the orbit the cycler must be on!

Second big question: while there is measured “water” content, bear in mind that it is coming from a combination of hydrated minerals plus a little bit of surface-implanted solar wind molecules, and it is down around 1% by mass. That’s what the Hayabusa results indicate. That is a sparse resource that (1) requires processing a huge bulk to get a small return, and (2) requires a high energy in the form of concentrated heat for that processing, that is proportional to that large bulk and not so much to the small resource recovered. You must heat (all the bulk) the minerals to un-hydrate them, releasing a small amount of steam. The required temperature is usually close to the incandescence point (near 1200 F = 650 C). Given those facts, why would such a resource be in the least attractive for recovery?

Third big question: this body is rather certainly a loose rubble-pile of small particles (boulders, cobbles, gravel, etc.), with no binding but mutual gravity between them. Because it is so small, that binding gravity is vanishingly-weak! Indeed, the best interpretation of the Hayabusa findings is that Itokawa is a contact binary, accounting for its bent peanut shape. Under those circumstances, I have to wonder exactly how you would implant any sort of habitation upon or within it, and expect it to stay there? Our seemingly-unexpected experience at “Didymoon” (although I expected it) would seem to confirm my interpretation of the disruption risks at Itokawa.

Fourth big question: given its rubble-pile nature, how do you dock with any sort of habitation upon or within Itokawa, when the slightest applied force could well disrupt the asteroid into a free-flying cloud of particles? Or at least detach or excavate the habitat from the rubble pile? The typical language of “space rocks” used up to now about asteroids and comets is actually very self-deceiving: these “rubble-pile” things are completely outside any Earthly experiences we humans have ever had. They are not “rocks” in any prior sense of that word.

(And these same two big questions apply to asteroid mining proposals as well.)

I posed these comments as questions to emphasize the fact that they demand answers before we can effectively plan missions that attempt utilization of these objects. Those are answers that no one anywhere yet has!

Given the unanswered nature of these big fundamental questions, I pose a 5th question: why is it prudent to explore the “cycler orbital” question (my first big question) by doing calculational work, when there would seem to be little advantage to be gained trying to use a rubble pile body as a site for a habitation of some kind (questions 3 and 4)?

Here’s a 6th question that I pose: given the unknown difficulties cited in “big questions” 3 and 4, why bother trying to put your cycler habitat upon or inside one of these celestial bodies (assuming one even exists with the right orbit)? Why not just build the habitat as a free-flying item? And give it course-correction capabilities, because close planetary fly-bys will disturb its orbit.

7th question: for radiation protection, how thick a layer of fiberglass batts and Kevlar cloth do you need, to get to 20 g/sq.cm of low molecular weight materials? A meter? So what?

Recommendation: forget trying to use asteroids as cyclers, just go with a free-flying habitat located in the right orbit for a cycler (whatever Aldrin came up with). Make it cylindrical 56 m diameter, spin it in rifle-bullet-mode at about 4 rpm for about 1 gee at the periphery, and make it long enough to be sure its baton-spin-mode moment of inertia is nowhere near the same as its rifle bullet-spin-mode moment of inertia. (Why? Having them the same invites spin instability.) Then wrap it with that meter-or-so of fiberglass batts and Kevlar cloth, because you need thermal insulation and meteor protection, as well as radiation shielding for solar flares and GCR. Then fit it with some high-Isp propulsion, with adequate propellant quantities to support course corrections.

We don’t need any asteroid properties or experience to do this! But high-Isp propulsion that is also high-thrust, would be a real boon.

GW

Last edited by GW Johnson (2024-10-09 15:01:44)

Calliban · 2024-10-09 16:37:26

Two questions here then really. (1) How do we do asteroid mining? (2) Is it worth doing as a way of building a cycler, rather than launching a station from Earth? I don't have definitive answers for either. But I have given asteroid mining some thought. Maybe its time to start talking about that again and developing it a bit further.

The asteroid itself is useless as a cycler in its natural state. Nor is burying anything in it a viable option. Making use of it means scooping up material and turning it into useful metals that we can build things out of. If we can do that, humanity has a bright future in space. If we can't, then really sending humans into space is a waste of time. If it isn't possible to use the resources that are there then there is no point going. The same is true for anything we build on Mars.

Regarding hydrated minerals. I don't think there is any doubt that sourcing water in this way is energy intensive. The reason that it may be worth considering is that water in the inner solar system is a rare commodity. We need it to survive and we need hydrogen to make all sorts of end products. Trying to cook water out of hydrated salts is like trying to extract water from Sahara sand. But if that is the only water source there is then it is better than none at all. For most stony asteroids, 'none at all' is what there is. So a slightly hydrated asteroid beats them as a resource, even if it is a crap one by Earth standards. The same is true of lunar polar water deposits. This is actually a pathetically weak resource in a hostile environment. But people are going after it because they need it and it is all that there is.

Last edited by Calliban (2024-10-09 16:46:54)

tahanson43206 · 2024-10-09 17:41:01

For Calliban re #43

It's been a while, but there was a period when you were really in a flow state as you thought about asteroid mining.

Your creativity stimulated others, and we have quite a collection of images for various ideas, assuming they are still being served by imgur.com.

One idea that came up was to inject water into a rubble pile asteroid using a perforated rod. The idea was (and is) to inject water (gently) into a rubble pile, let it freeze, and then (gently) pull the icicle out. If all goes to plan, the rod should be surrounded by a solid mass of material that can then be added to a large collection for shipment to a processing facility, or perhaps just shipped to a processing facility as is.

Unfortunately, like so many ideas that appear on the forum, it faded from view and I appear to be the only member who still remembers it.

(th)

GW Johnson · 2024-10-10 08:18:55

Calliban:

Actually, I agree with you in many ways. You use what is there. Wherever it is.

I don't know of what usefulness there is to C- and S-type asteroids, since you have to heat the particles past incandescence to extract the steam and the carbon. But the M-types might be very useful for extracting metals. The energy cost of refining products from those raw metallic materials would be comparable to refining on Earth, although conditions in space are tougher. However, the quality of the ore is likely very much higher, with low oxide content. That would be a distinct advantage.

The M-types apparently are more like a monolithic object, and the known ones are usually quite large, so we might need to do our ore extractions with some sort of "death ray" to cut pieces of manageable size loose.

If carbon and water ice are the goal, I would point to the larger moons of Jupiter and Saturn (perhaps excluding the special case of Titan, the others are airless) as worthy goals. The hardest part of doing that is the long travel time to destinations that far away, followed by the difficulty of surviving the radiation environments (applies to machines as well as men), followed by surviving the intense cold (more of a problem in the atmosphere on Titan).

I think there might be lots of water ice on Mars, if you land in the right places. Apparently there are a lot of iron nodules on the surface in many places, which could be easily scooped up, and constitute a fairly high-grade ore to refine. On Mars, it's harder to stay warm than it is in vacuum, but at least the atmosphere is low density (unlike Titan), so the convection coefficients are low.

The biggest problem with metal refining off Earth is coping with low or no gravity, and no atmosphere or atmospheres without oxygen to use. We will have to develop the right processes for this. And develop them to the point of readiness for industrial application. A lab demo ain't it.

GW

Void · 2024-10-10 17:32:42

I have been considering your favor of type "M" asteroids Dr. Johnson, and you have converted me, I think.

I have considered that they are often substantial in size but not too big.

I am also considering a "Mond" Process to drill into them. They probably are not entirely drillable by the Mond Process, but that and other methods may allow extensive tunneling into them while the tunnel waste would not be waste.

There is some chance that they will have much of what is needed in the spectrum of materials, and anyway other asteroids that cross paths with them will have what else is wanted.

The Iron can be a propellant and a building material it seems, so I am going to borrow from you for this elsewhere.

I would hope that Uranium and Thorium might be included. So then with that power source(s) and Iron and other propellants, access to the outer solar system might be secured nicely, I think.

Ending Pending

Last edited by Void (2024-10-10 17:35:51)

Calliban · 2024-10-11 06:16:52

GW, my concept for mining rubble pile asteroids is shown here.
https://newmars.com/forums/viewtopic.ph … 95#p227195

It took me a while to come up with a way of mining something that cannot sustain any shear stresses on its surface. The way weakly conglomerated rubble piles behave when disturbed, has more in common with liquids than how we expect solids to behave.

We still need to discuss how mined materials can be processed into something useful. But one step at a time.

kbd512 · 2024-10-11 14:23:05

This paper is from 2003, but outlines trade studies associated with using Aldrin Cyclers. The cost figures are now wildly erroneous due to the much lower launch costs enabled by SpaceX's fully reusable Starship.

Interplanetary Rapid Transit to Mars - Global Aerospace Corporation, Colorado School of Mines, Science Applications International Corporation

Falcon 9 achieves $5,500/kg. That's what SpaceX actually charges their customers, rather than what it costs them, which is $2,720/kg.

Falcon Heavy achieves $1,500/kg. This is below the theorized possible cost reduction in the paper linked above, and how it might make ISRU less relevant (it doesn't, but this was their line of rationalization back in 2003).

Starship was initially estimated to cost $100/kg to $150/kg to LEO, but delivering 1kg to Mars requires 8 flights, so $800/kg to $1,200/kg delivered to Mars. That cost figure is still far too high to sustain a colony, so we must figure out how to use electric propulsion and/or cyclers to knock that cost back down to $100/kg to $150/kg. If each Starship launch truly does end up costing $2M, then that's $10/kg to LEO. That means $80/kg to Mars, which, in my opinion, is still too high. The great object of our propulsion technology advancements should be to drive delivery costs into the ground, so that delivering 1kg to Mars is no more expensive than air mailing 1kg from one continent to the next.

I learned something about our mail and parcel service today that I never knew. Here in the US, if the mail in question must be delivered beyond a reasonable overnight driving distance, then all mail of reasonable size and weight will be delivered by air, period. They apparently load the mail onto planes already bound for the destination cities, so the cost of fuel for air delivery is already included in the cost of the stamp. If the city in question is larger, then it will have more planes and more frequent flights bound to those destinations, so it works out. If you send a letter from New York to LA, they don't bother with long haul trucking. They drive the mail to the nearest airport, there are flights from New York to LA every day, so that's how it arrives in LA. Presumably, if you sent a letter from LA to Japan, then the next flight leaving LA has the mail on board. That's actually a pretty good model, but it implies that there are lots of people headed in the same direction.

Berlin had the "Berlin Airlift" to sustain life when the going got tough. We need a "Mars Spacelift" effort directed at colony sustainment. We'll need to launch both ways, conjunction and opposition, meaning coming and going, we'll need rail guns or light gas guns and lasers to deliver metals and volatiles, as well as cyclers, some devoted purely to cargo, others carrying people and cargo.

Design of a rapid transit to Mars mission using laser-thermal propulsion

A 10m diameter 100MW phased array laser-thermal concept will allow a 1,000kg payload, launched via Falcon 9, to reach Mars in 45 days. The laser is ground-based and heats H2 propellant aboard the orbiting satellite / spacecraft to temperatures sufficient to achieve 3,000s Isp, similar to a low performance gas core nuclear thermal rocket, such as the "nuclear lightbulb" concept. The laser can direct its power onto the heat exchanger at distances (through the atmosphere) of up to 50,000km. I would say we put that thing in space so that we have an unobstructed line-of-sight to the spacecraft. An onboard supply of LOX/LH2 can be combined in a fuel cell to deliver the power to the laser. If a Starship can deliver "priority mail" parcels to LEO for $10/kg, and then the laser heats a small amount of LH2 to 10,000K to generate thrust, then the payload can complete the trip at very high speed. Alternatively, we could use reduced acceleration rates and heat shields to deliver far greater tonnage of cargo over the standard 6 months of transit time, vs 45 days. The part of the vehicle that remains in-orbit is fully reusable, so it can be refueled at Mars and returned to Earth.

Calliban · 2024-10-11 18:59:35

Kbd512, I havn't read your links yet; I will do tomorrow. Cyclers are pretty much useless for transport of freight. These are really just space stations on orbits that make close approaches of planets. Having a fixed orbit saves having to spend fuel on every trip. Cyclers are useful for transporting people, who need comfortable, radiation shielded environments, preferably in gravity and with as much living space as possible. But using a cycler to transport freight won't save any propellant. If the freight is live animals, or plants or tissue samples, then a cycler could cut total cosmic ray doses to that freight. But they actually increase dV.

Ultimately, cyclers could be a good way of transporting people between planets once we have enough of them that people can use small transfer vehicles to travel between them. With enough cyclers, the time from Earth to Mars and back again, should be not much more than it woukd be using an interplanetary ship. But the cycler is an order of magnitude more comfortable. Essentially a flying hotel. We can do that because once established on its orbit, no more propellant is needed. It just follows a permanent elliptical orbit that grazes the orbits of Earth and Mwrs.

Last edited by Calliban (2024-10-11 19:01:51)

tahanson43206 · 2024-10-12 05:59:14

For Calliban re #49

It is possible for you to make a small improvement for your post...

A reader might be misled to think that no propellant is required to keep a cycler on course.

As GW Johnson pointed out recently, and as many others have pointed out, cyclers will require course adjustment due to the forces at work on them as they move through space.

Your statement is correct in the sense that a cycler could be set in motion and never adjusted, but it's value would decrease over time.

(th)

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