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#1 2019-09-04 10:05:45

tahanson43206
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Registered: 2018-04-27
Posts: 3,574

Aldrin Cyclers and Asteroid Belt Cyclers

SearchTerm:AldrinCycler
SearchTerm:Cyclers

Mission statement for this topic:

This topic is intended to consolidate (as much as possible) all of the many contributions already present in the NewMars database of posts.

In addition, it is intended to provide a guide for an entrepreneur or for a serious student who wish to learn about the topic, and hopefully to make investments of time, energy and eventually funds, to bring the concept to reality.

Edit 2019/09/09 Earth time: This topic will be eligible for closure when the first working Cycler completes a full circuit, from Earth to Mars and back.

Text below was entered when this topic was created:

For SpaceNut ...

Is there a way to search the Interplanetary Transportation Index level topic, to see if anyone has already created a subtopic about cyclers?

The search I did for the Index topic yielded 23 pages of results, and that is too many to examine "by hand".

if this is the first subtopic with focus specifically on cyclers, then here is what I am hoping members will contribute:

Goal: To assemble knowledge needed by an entrepreneur to found a transportation company using cyclers for Solar system travel

Validation: An entrepreneur creates a corporation to supply transportation services to Mars using a cycler.

There is already substantial work on record for the Aldrin Cycler concept for Mars transportation.

Yesterday (Earth time) I found a section of John S. Lewis' book on Mining Asteroids, devoted to the subject of cyclers for Asteroid Belt access.

In particular, I was struck by the notion of adapting an existing asteroid to serve as the feedstock for a cycler.

This notion is of particular interest (to me at least) right now, because a new member (Calliban) has initiated a conversation about harvesting an asteroid, and because the notion of visiting Apophis is gaining currency due to it's near-Earth pass in 2029.

Apophis might have the features that would make it an attractive subject for a study on how it might be adapted for a cycler to Mars.

***

Tip of the hat to RobertDyck, who recently "launched" a new topic devoted to space going passenger liners which would use traditional propulsion methods to provide transportation to and from Mars.

(th)

Last edited by tahanson43206 (2019-09-09 07:49:05)

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#2 2019-09-04 15:19:21

RobertDyck
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From: Winnipeg, Canada
Registered: 2002-08-20
Posts: 6,163
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Re: Aldrin Cyclers and Asteroid Belt Cyclers

Click "Search". Under "Keyword search" enter "cycler" (without the quotes). Under "Forum" check "Interplanetary Transportation". Under "Search in" select "Message text and topic subject". Under "Show results as" select "Topics". Click "Submit"; it will give you every mention of cyclers.

Habcrafts and Cyclers

Cyclers

Cycling Spaceship

Aldrin's Cyclers

Why not a cycler?

Crew Transfer in Orbit

Cycler Spaceships - Ships going between Earth and Mars

LEO to TMI - discuss

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#3 2019-09-04 17:00:37

SpaceNut
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From: New Hampshire
Registered: 2004-07-22
Posts: 19,728

Re: Aldrin Cyclers and Asteroid Belt Cyclers

Thanks RoberDyck for the assist....
Cyclers rely on resonance to make the passes by each location occur at fixed intervals.
Any speed changes will make it off course in just a single pass.
The course can also be altered by passing comets and large meteors as seen by maven with mars atmospher.
This makes them very slow for transit due to distances of each location that we are trying to intersect with.

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#4 2019-09-04 18:05:03

tahanson43206
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Posts: 3,574

Re: Aldrin Cyclers and Asteroid Belt Cyclers

For RobertDyck re #2 ...

Thanks for the tutorial on using the search capabilities ... it's past time (for me) to learn about them.

And thanks for the list of topics .... if my new topic is redundant (as seems likely) I'll move to other more pertinent ones.

Your contribution makes this topic helpful to future visitors to the forum.

For SpaceNut .... my understanding is that the long orbits are designed so that the passage to or from Mars is a small part of the total orbit.  The figure of 157 days sticks in my mind, but I'd have to go back to the Aldrin (and company) pdf to confirm that.

The vehicle would (presumably) be operated so that perturbations would not prevent arrival at the planned destination on or close to schedule.

This vehicle type seems a strong candidate for robust ion engines operating continuously in the gravitational cross-currents of Solar System travel.

For individuals who like the challenge of space navigation for a career, this vehicle type would seem to be worth considering when they become available.

(th)

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#5 2019-09-04 18:37:10

kbd512
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Re: Aldrin Cyclers and Asteroid Belt Cyclers

Some form of high-Isp propulsion system is the only practical propulsion system for colonizing Mars.  We should only expend chemical propellants in traditional rocket engines for surface launches.  If SpaceX builds a 1000t class ultra heavy lift launch vehicle, then cyclers or purpose-built interplanetary transport ships are ideal.  Yes, I just made up the UHLV term and choose to classify UHLV's as vehicles capable of lifting more than 250t to orbit.  These ships would off-load some of their power generation requirements for orbital transfer on both ends using multi-MW class solar power satellites to provide high-thrust and NERVA class Isp chemical propulsion.  Beyond the main belt, onboard fission reactors would be required, with the unfortunate effect of drastically reducing useful payload.  The solar power satellites would use microwave power transmission and the ships would use propellant heat exchangers.  Something like VASIMR would provide cruise propulsion.

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#6 2019-09-04 19:04:50

tahanson43206
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Re: Aldrin Cyclers and Asteroid Belt Cyclers

For SpaceNut re #2 ...

Aldrin's Cyclers

I started this link from the list created by RobertDyck, and it deteriorated as i went along.  This series started back in 2005, and it contained a number of interesting posts, including one which reported that an Adrin Cycler crosses the orbit of Mars at a 90 degree angle.  THAT was a surprise!  The velocity difference to be overcome by "taxi" craft was significantly greater than I was expecting as well.  The discussion included mostly objections to the concept, but one author did report that other cycler designs are (apparently) available.

The problem I encountered is that the posts seemed to be drifting to the right and out of view as I went along.

For kbd512 re #5 ...

The kinds of high-ISP ion systems in existence, or in development today, were not available when Dr. Aldrin first developed his concept.  I hope to learn how they might impact design of the cyclers themselves, and (perhaps more importantly) the Taxi craft which have the daunting task of moving people and goods to and from the cycler as it passes its destination.

(th)

Last edited by tahanson43206 (2019-09-04 19:09:35)

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#7 2019-09-04 19:28:03

SpaceNut
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Re: Aldrin Cyclers and Asteroid Belt Cyclers

Ion, Vasimr are both trading energy for fuel in the rocket speed equation.

https://en.wikipedia.org/wiki/Mars_cycler

220px-Aldrin_Cycler.gif

2 cycler configuration
220px-Aldrin_Cycler_2.gif

or go for more to allow for more opportunity to go and return.

A LOW-THRUST VERSION OF THE ALDRIN CYCLER
https://engineering.purdue.edu/people/j … Cycler.pdf

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#8 2019-09-05 08:02:03

tahanson43206
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Posts: 3,574

Re: Aldrin Cyclers and Asteroid Belt Cyclers

For SpaceNut re #7

Thanks for this helpful set of images from the Wikipedia article! 

For GW Johnson .... The advantage of a cycler is that there is the opportunity to build up a massive habitat over time, with 1 G simulated gravity and Earth sea level radiation protection, along with ocean cruise standard accommodations such as cuisine, entertainment, education and physical activity.

Anything less than that will be cramped and limited in attractions for wealthy clientele.

That said, the kind of large ship RobertDyck is proposing seems (to me at least) quite competitive for funding, so I hope to see that topic fill out with substantial contributions.

I am interested in the prospect of using intelligent momentum transfer to deal with some of the challenges that come with the cycler design.

It seems possible (without anything other than intuition to work with) that a pair of payloads rotating on a tether as a cycler approaches Mars could release the pair so that each goes somewhere useful. 

The same concept would work in ballistic launches from Earth.  If the goal is to deliver a ton to GEO, then a tether could release that ton to match the horizontal vector needed for GEO, while the matching ton is released in the opposite vector.  In the case of Earth, that ton would fall back into the gravity well, but at Mars a well chosen vector might put the matching mass somewhere useful.

I hope to see forum members with the requisite mathematics skills and access to the appropriate computer equipment to develop analysis of these possibilities.

If readers with the needed skills are not yet members, now is a good time to take the plunge.

You have nothing worse to fear than an attack for your politics.  Just avoid politics and you should be fine!

(th)

Last edited by tahanson43206 (2019-09-09 20:14:42)

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#9 2019-09-05 11:50:46

GW Johnson
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From: McGregor, Texas USA
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Posts: 4,078
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Re: Aldrin Cyclers and Asteroid Belt Cyclers

Well,  building a huge habitat may or may not require going to a cycler.  You are just building the equivalent of an ocean liner that flies in space.  There really is a way to do that:  nuclear explosion propulsion.  That has its own limits or restrictions on use.  But we have known since 1959 that it would work.  It just works best at gigantic scales,  which is really why we have never used it.

Look for yourself at the mass ratio and delta vee capability for something in the 10,000-20,000 sec Isp range with a vehicle thrust/weight in the 2-4 gee range!  Yep,  it's hard to hold it down to 2-4 full gees!  I think you will really like what you see.  These are built out of heavy steel plate the same way armored warships are,  and can be launched from Earth's surface,  starting with fractional-kiloton devices. The yield goes up as you fly up into vacuum.

There are side effects to nuclear explosion propulsion.  Everybody thinks about nuclear fallout,  but that is NOT the big one.  EMP is.  These have to built and launched from very isolated locations,  and flown into space such that the ground track stays very isolated.  And you can't stop in low Earth orbit,  you must park it higher up to dilute the EMP with distance squared.

I'd caution against notions of building these or any other structures out in space from asteroid materials.  No one yet knows how to make real engineering materials out of rocky debris.  Those who say we know are lying to you.   So far,  stones are for masonry,  and such cannot serve as pressure vessels or take anything but a compressive load. Sorry,  that's just where we humans are.

GW

Last edited by GW Johnson (2019-09-05 11:56:31)


GW Johnson
McGregor,  Texas

"There is nothing as expensive as a dead crew,  especially one dead from a bad management decision"

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#10 2019-09-06 06:27:10

Calliban
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From: Northern England, UK
Registered: 2019-08-18
Posts: 532

Re: Aldrin Cyclers and Asteroid Belt Cyclers

Clearly there are pros and cons with the use of cyclers.  Using a cycler inevitably results in higher mission dV requirements, because fuel must be burned matching the cycler orbit and adjusting orbit again upon approaching destination.  Additionally, using a cycler implies waiting for its orbit to align such that it makes a close pass at Earth followed by a close pass at Mars.  This would make journeys to and from Mars irregular; you may need to wait years for the orbits to line up in a way that makes the cycler a viable tool.

Some advantages I can see with this approach:

1. The bulk of an asteroid shields the crew from radiation and thermal cycles for at least part of the journey.

2. The cycler may be a destination in itself.  If asteroid mining can be carried out for minerals that can be delivered to Earth orbit, then building the cycler can be subsidised by the profits made from those materials.

3. Most asteroids contain silicates; some contain carbon and water.  It may be possible to manufacture some consumables for the mission using material mined from the cycler.  This might include oxygen, propellants and maybe even food grown on the cycler.

4. Using a cycler reduces the requirements placed on the interplanetary transfer vehicle.  Instead of being suitable for an entire journey, it need only be sufficient to transfer people to and from the cycler, which are presumably much shorter journeys than the entire trip. If transfer times are no more than a week say, it might be tolerable for people to endure cramped conditions, like the interior of an airliner cabin.  No one could survive that for eight months, but a week might be tolerable without driving people nuts.  The accommodations on the cycler could be far more comfortable - more like a small town than a spaceship.  Tahanson, SpaceNut and I have discussed a scheme for structurally reinforcing small asteroids to allow tunnels to be pressurised.  There is even the option for artificial gravity, though this is more difficult.

5. Whilst alignments between the cycler and individual planets are irregular, the use of the cycler would be more optimised if we are interested in multiple destinations.  If a cycler allowed close approaches to main belt asteroids, that would be a valuable bonus.  If we can refuel from the cycler, using propellants derived from the cycler, it might even be possible to use it as a springboard for journeys to Jupiter and the Trojans.  These sorts of things imply that the cycler would have a limited useful life as we use it up.

Last edited by Calliban (2019-09-06 06:40:23)


Interested in space science, engineering and technology.

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#11 2019-09-06 06:47:29

Calliban
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From: Northern England, UK
Registered: 2019-08-18
Posts: 532

Re: Aldrin Cyclers and Asteroid Belt Cyclers

GW Johnson wrote:

Well,  building a huge habitat may or may not require going to a cycler.  You are just building the equivalent of an ocean liner that flies in space.  There really is a way to do that:  nuclear explosion propulsion.  That has its own limits or restrictions on use.  But we have known since 1959 that it would work.  It just works best at gigantic scales,  which is really why we have never used it.

Look for yourself at the mass ratio and delta vee capability for something in the 10,000-20,000 sec Isp range with a vehicle thrust/weight in the 2-4 gee range!  Yep,  it's hard to hold it down to 2-4 full gees!  I think you will really like what you see.  These are built out of heavy steel plate the same way armored warships are,  and can be launched from Earth's surface,  starting with fractional-kiloton devices. The yield goes up as you fly up into vacuum.

There are side effects to nuclear explosion propulsion.  Everybody thinks about nuclear fallout,  but that is NOT the big one.  EMP is.  These have to built and launched from very isolated locations,  and flown into space such that the ground track stays very isolated.  And you can't stop in low Earth orbit,  you must park it higher up to dilute the EMP with distance squared.

I'd caution against notions of building these or any other structures out in space from asteroid materials.  No one yet knows how to make real engineering materials out of rocky debris.  Those who say we know are lying to you.   So far,  stones are for masonry,  and such cannot serve as pressure vessels or take anything but a compressive load. Sorry,  that's just where we humans are.

GW

NASA are developing a Z-pinch based fission-pulse device, in which much smaller masses of fissile material are compressed to enormous density using electric fields.  The advantage here would seem to be that fission takes place at much lower explosive yield without sacrificing efficiency.  The reaction takes place within a magnetically lined thrust chamber and thrust can be augmented by feeding hydrogen propellant into the chamber.  The concept is still inherently pulsed, but this would appear to take care of the EMP problem and at least partially mitigate the radioactive contamination issue, given that fission energy is more efficiently used to produce thrust.


Interested in space science, engineering and technology.

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#12 2019-09-06 15:39:37

GW Johnson
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From: McGregor, Texas USA
Registered: 2011-12-04
Posts: 4,078
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Re: Aldrin Cyclers and Asteroid Belt Cyclers

I know nothing about this Z-pinch thing.  I'm an old guy,  out of the business for some time now. 

The old 1950's nuclear explosive technology used a uranium or plutonium fission device,  but with the reflector reshaped to get a spindle-shaped blast distribution.  One blast spindle prong points directly at the pusher plate,  the other directly away.  On the side of device facing the pusher plate was a big lump of polyethylene,  to provide reaction mass the bomb could accelerate into the pusher plate. 

It was this directed spike of energy and matter toward the pusher plate that made the device efficient.  An omni-directional blast would be far less efficient,  and less efficient at pushing the reaction mass,  too.  Omni-directional is what you want for a blast weapon.  This shaped charge thing makes for efficient propulsion,  but a poor blast weapon.  It's fairly easy to tell them apart if you look at the reflector geometry.

Clearly the orientation of the device,  as well as its range,  at explosion is crucial.  You don't just fling it out there,  it has to be ejected in a very controlled fashion.  These were a few-kiloton-range devices in space,  fractional kiloton down in the atmosphere.  They were ejected and exploded at 2 to 10 per second,  in the various designs.  The pusher plate connected to the rest of the ship with giant shocks and springs,  which evened-out the pulses into something tolerable.

GW

Last edited by GW Johnson (2019-09-06 15:44:43)


GW Johnson
McGregor,  Texas

"There is nothing as expensive as a dead crew,  especially one dead from a bad management decision"

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#13 2019-09-06 16:01:16

SpaceNut
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Posts: 19,728

Re: Aldrin Cyclers and Asteroid Belt Cyclers

Its a modified ion field engine where we are making it work as if its plasma after the grid directs the fuel which is compressed out the nozzle. The issue is the field energy requires a reactor to provide the power which means a means to cool it is required. The mass of the ship just went way up as solar and batteries will not be of a long enough energy level for it to comress or to direct the particles in the direction of the exit....

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#14 2019-09-07 11:46:49

GW Johnson
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From: McGregor, Texas USA
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Posts: 4,078
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Re: Aldrin Cyclers and Asteroid Belt Cyclers

Old Project Orion's nukes were under 300 lb for a 5 KT device.  You have to have big heavy shocks and a huge pusher plate,  and your hull needs to be hell-for-stout to take the loads,  but your propellant supply is quite compact,  actually. 

Orion was roughly 25% pusher and shocks by weight,  25% nuke "propellant",  25% payload,  and 25% other inerts.  In large sizes,  extreme Isp (10,000+ sec) at multiple-gee acceleration capability.  I'm not sure anything can beat those characteristics.  They make up for a lot of fallout and EMP effects. 

GW


GW Johnson
McGregor,  Texas

"There is nothing as expensive as a dead crew,  especially one dead from a bad management decision"

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#15 2019-09-08 06:39:10

tahanson43206
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Posts: 3,574

Re: Aldrin Cyclers and Asteroid Belt Cyclers

For SpaceNut and others who may be interested ...

I have updated the launch post for this topic, to include search term strings, and a mission statement.

***

For GW Johnson ...

Thank you again for your offer of the spreadsheet you created to compare propulsion options for large never-landing space vehicles.

I'm wondering what you might think of exporting the spreadsheet in CVS format, and posting the resulting file as an update to an existing post in this topic.

The reason for adding the file to an existing post is that it will be large, so adding it to an existing post will not bring it to the attention of forum readers who follow the active list.   The FluxBB forum software should be able to handle a large update such as this would be.

On the other hand, the update attempt may fail, because FluxBB may have limits we don't know about.  If you update an existing post, only you will know if it failed.

Then, assuming the post is confirmed, you can create a small post here or in RobertDyck's space liner topic (or both) announcing its presence.

(th)

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#16 2019-09-08 08:40:34

SpaceNut
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Posts: 19,728

Re: Aldrin Cyclers and Asteroid Belt Cyclers

This forum under the existing format does not do file up loads of any sort as that would allow for hacking to occur and infection of the site.
Post the link to the file on GW website will work like any other...
Then its up to the computer of the user to have the software to open it.

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#17 2019-09-08 09:36:25

tahanson43206
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Posts: 3,574

Re: Aldrin Cyclers and Asteroid Belt Cyclers

For SpaceNut re #16

Thank you for your suggestion.

However, I'd like to try to make a pitch (again) for the CVS format.  This is a format which can be uploaded to any spreadsheet package.

However, I do NOT know if it handles formulas well, since I've never tried to use if the that kind of data.

For GW Johnson ...

If you are willing to give SpaceNut's suggestion a try, I'd be happy to see if the file can run on any of the systems available here.

(th)

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#18 2019-09-08 10:45:21

GW Johnson
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From: McGregor, Texas USA
Registered: 2011-12-04
Posts: 4,078
Website

Re: Aldrin Cyclers and Asteroid Belt Cyclers

I can sent the excel.xlsx type spreadsheet file to someone to experiment with.  But I need an email to send it to. 

But all this talk about CVS and FluxBB and the rest is a mystery to me.  When I entered the workforce,  we were all still using slide rules.  I don't know much more than monkey-see,  monkey do with this computer stuff.  I don't know how to use more than about 10% of the stuff on a graphing calculator. 

If you want,  I can post text and images at "exrocketman",  but I do not know how to post downloadable files there.  Images you can download.  I've already posted there articles on how to do rocket equation estimates and real-world nozzle ballistics. 

GW


GW Johnson
McGregor,  Texas

"There is nothing as expensive as a dead crew,  especially one dead from a bad management decision"

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#19 2019-09-08 11:33:33

tahanson43206
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Re: Aldrin Cyclers and Asteroid Belt Cyclers

For GW Johnson re #18 ...

It is possible SpaceNut might be willing to accept the XLS file. 

In the meantime, I have a question that might be a better fit ... at least I hope so.

Some time back, I recall your writing (here or on the blog) about working on the Scout solid fuel rocket.  My recollection is that you and the planning team used a kind of trial and error method to compute the correct angle to point the Scout to achieve a particular launch objective.

You are writing in the Aldrin Cyclers topic, which I set up in hopes of drawing on the collective wisdom here to provide useful tips for future entrepreneurs.   In learning more about Cyclers, I've learned that one of the characteristics of a Cycler flight pattern is that it passes its destination (Mars, the Earth or an asteroid belt object) at a pretty good clip.  A figure to work with is 12 kilometers per second.

A Cycler is a massive ship with rotation for gravity simulation, radiation shielding to Earth sea level standard, amenities similar to RobertDyck's vision of a space going liner, and with other characteristics I'm still learning about.   Such a ship is going to be making very small course adjustments in order to maintain the desired flight plan.

This leads me to my question:  Can you imagine a small, solid rocket personal transport system able to carry a single passenger and needed survival supplies and equipment for a docking at Phobos, or at a space station in Earth LEO?

What I'm imagining here is that the landing/docking pod would be shipped up to LEO with the passenger from Earth, as part of the necessary equipment that person would need for a flight to Mars via the Cycler.   The device would be programmed while the Cycler is in flight, to accomplish the deceleration and docking needed at Mars.  I am proposing Phobos because Mars is going to want incoming passengers to stop in quarantine facilities before they mix their germs with the Mars population.

Regular passenger transport services from Phobos to Mars and back will be a predictable feature of a mature Mars infrastructure.

A solid fuel rocket, similar to the Scout but perhaps with just one stage? should be able to deliver a passenger from the Cycler to Phobos.

Do you agree, and if so, can you estimate the requirements for the system?  To answer the first question that a designer might ask, I think a metric ton might be within the reasonable ballpark for the passenger, equipment and supplies.

Thanks again for your support of this topic!

(th)

Last edited by tahanson43206 (2019-09-08 11:35:37)

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#20 2019-09-08 12:16:34

GW Johnson
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From: McGregor, Texas USA
Registered: 2011-12-04
Posts: 4,078
Website

Re: Aldrin Cyclers and Asteroid Belt Cyclers

Tahanson 43206:

Well,  first you must understand THE fundamental characteristic of a solid:  once you light it, you CANNOT turn it off!  It will burn to completion the same as a stick of dynamite,  just a lot slower than the dynamite.  Accordingly,  you do not have precise control over your vehicle's burnout velocity.  It is what it is.  And that varies a single handful of percent as conditions vary.

For purposes of rocket equation-type estimates,  think Isp in the 200-220 sec range for double-base propellants,  and 240-260 sec for AP-oxidized composite propellants.  Those data are for sea level or modest-altitude nozzle designs typical of missiles.  Ratio them up by the vacuum/sea level thrust coefficient ratio for vacuum designs. 

There is something called a composite-modified double-base propellant (AN oxidizer added),  and there are also AP-oxidized composite-modified double-base propellants (at a hugely-increased risk of catastrophe during processing).  These fall in-between the Isp ranges I already quoted.

By "double-base" I mean pelletized nitrocellulose gelatinized into a plastic by flooding it with raw nitroglycerin.  It might or might not have powder aluminum and other minor trace powders added to the pelletized nitrocellulose.  These are real sympathetic detonation hazards,  but respond better to immersion in fuel fires.  Some are class 1.1 mass-detonable explosives,  others can be the less-sensitive class 1.3 explosives. 

By composite I mean powder oxidizer and maybe powder aluminum,  plus other trace powder additives dispersed into a polymer binder that is cured by heat and chemistry.  These are nearly always only the less-sensitive class 1.3 explosives,  as long as the binder is an ordinary hydrocarbon polymer.  They tend to be relatively insensitive in sympathetic detonations tests,  but respond rather badly to fuel fire cookoff,  especially "slow cookoff".  The exception is glycidyl azide polymer (GAP) binder,  which is a class 1.1 monopropellant explosive all by itself.  It gets REALLY sensitive if you use AP as the oxidizer.

The older AN-oxidized composites have Isp much closer to the double-base range. 

By AN I mean ammonium nitrate.  By AP I mean ammonium perchlorate.  The sodium and potassium nitrate oxidizers are so obsolete today,  and so low-performing,  that they only belong in fireworks. 

I know less about double-base burn rates,  most of my experience being with composites.  But AN-oxidized composites generally fall somewhere near the 0.05-0.1 in/sec range,  while AP-oxidized composites generally fall nearer 0.5 to 1 in/sec.  Those are quoted at chamber pressures near 1000 psia.  As I understand it,  double base burn rates resemble AP-oxidized composite burn rates. 

For composites,  the higher burn rates are generally associated with higher solids loading and smaller oxidizer particle size.  Higher Isp goes with higher solids loading.  Processing cast viscosities get really high really quickly with higher solids loading.  You cannot sleeve cast them at higher solids loading,  you have to pressure-cast and pressure-pack.  Nobody does that anymore,  since the plant where I once worked closed.

With AP,  once you grind to something near or under 5 micron particle size,  you can no longer process the powder dry (extreme mass-detonation risk!).  You have to wet it into a slurry with a very-high molecular weight freon,  and then boil that freon out of the mix by the effects of mix vacuum,  something required with ALL composites.

Sorry,  actually making solids is a complicated world. 

GW

Last edited by GW Johnson (2019-09-08 12:19:49)


GW Johnson
McGregor,  Texas

"There is nothing as expensive as a dead crew,  especially one dead from a bad management decision"

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#21 2019-09-08 15:04:46

kbd512
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Re: Aldrin Cyclers and Asteroid Belt Cyclers

Well...  We went from "we need better propulsion for big ships" to "we need steel ships that can withstand nuclear explosions".  Is there anything else, short of a nuclear explosion, that we could feasibly use to power these things?

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#22 2019-09-08 15:36:52

GW Johnson
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From: McGregor, Texas USA
Registered: 2011-12-04
Posts: 4,078
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Re: Aldrin Cyclers and Asteroid Belt Cyclers

Kbd512:

The best numbers I can generate say that either explosion propulsion,  or ion propulsion,  are the only known propulsion options for a really big orbit-to-orbit colonization ship.  Nothing else known comes close,  in terms of ignition mass divided by dead-head payload mass. 

There is no way around that,  it's just physics.  Nuclear thermal (as in NERVA) is just NOT a practical option for a really large colonization ship.  Nothing else is actually known at this time in history. 

And that conclusion says NOTHING about what might be desirable for a small exploration ship!!!  For that mission,  ignition mass/payload mass does not matter much,  if at all.

If explosion propulsion is selected,  yeah,  it has to be hell-for-stout,  which also inherently provides solar flare (and GCR) shielding.  Massive size allows spin gravity,  no matter what you select.  This nuclear explosion propulsion option is inherently very massive to build,  and that also inherently confers a long service life. A century or more?

If ion propulsion,  the thruster array and its multi-MW-range power supply are the two massive propulsion items.  The rest is a rather gossamer structure.  That leads to a much-reduced service life,  and a limited-at-best radiation shielding characteristic,  which MUST be dealt with,  one way or another.  The very large size still allows artificial spin gravity. 

As best I can tell,  the design criteria,  and design constraint limits,  for radiation protection are 20+ g/sq.cm shielding (preferably with lower molecular weight materials).  If you bump into secondary-shower problems with heavier stuff than aluminum,  you need a place to retreat to,  to shield you from those effects as well.  If this shielding effect does not extend to all the manned areas,  then the flight control station is the top priority,  with the sleeping quarters a very close second. 

As far as I can tell,  the limits and constraints for artificial spin gravity are near-1-full gee supplied,  at least in the daily work stations,  and no more than about 4 rpm spin rate for untrained,  unacclimatized folks.  You do not need this in areas containing sleeping quarters!  This shades into no more than about 8 rpm for well-trained,  well-acclimatized folks.  Beyond about 12-16 rpm,  you quickly get into unacceptable blood pressure gradients head-to-toe in standing individuals.  Gees = (r-spin/56 m)(spin rate/4 rpm)^2. 

There are two (and only two) stable spin modes for any object (about the axes for min and max moments of inertia).  For most objects,  that translates into either spinning like a rifle bullet,  or spinning end-over-end like a baton thrown high during "Friday Night Lights" half-time shows. 

This picture is both complicated in detail,  and quite simple in terms of fundamental concepts.  Violate these design "rules" at your peril,  that's what the data really say,  so far.  Including what NASA has developed on ISS. 

GW

Last edited by GW Johnson (2019-09-08 15:43:35)


GW Johnson
McGregor,  Texas

"There is nothing as expensive as a dead crew,  especially one dead from a bad management decision"

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#23 2019-09-08 15:58:25

kbd512
Administrator
Registered: 2015-01-02
Posts: 3,728

Re: Aldrin Cyclers and Asteroid Belt Cyclers

GW,

I still think we need to invest more money in the fusion driven rocket- which doesn't attempt to extract a single Watt of electricity, it merely expels a high energy plasma out the rear end for thrust and uses metal, Aluminum or Lithium, as propellant.

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#24 2019-09-08 17:15:43

SpaceNut
Administrator
From: New Hampshire
Registered: 2004-07-22
Posts: 19,728

Re: Aldrin Cyclers and Asteroid Belt Cyclers

I have recieved other excel files from GW in the past but the problem still is I have no means to host them.
https://exrocketman.blogspot.com/

website builder in use
https://www.blogger.com/about/?r=1-null_user

The only file type that Blogger (formerly Blogspot) supports for its blogs are image files in the formats of JPG, GIF, PNG, TIF and BMP. Images uploaded over Blogger are saved online via Picasa. If you use an account there, notice that there's a folder with your blog's name, full of images you uploaded.

https://webapps.stackexchange.com/quest … on-blogger

It is not possible to upload files other than image and video files to Blogger. You would have to use other file sharing websites like Dropbox to share such files. Also, your Google Drive link works perfectly fine, feel free to use that link to share the same file with other people.

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#25 2019-09-08 18:00:50

tahanson43206
Moderator
Registered: 2018-04-27
Posts: 3,574

Re: Aldrin Cyclers and Asteroid Belt Cyclers

For SpaceNut re #24 .... Would Mars Society management approve your setting up a Dropbox account for the forum?

My recollection is that the free basic package allows up to 2 Gb of space.

I have a couple Dropbox accounts, one of which was set up for a non-profit organization, so I know the concept works.

If you are the only one who posts to the Dropbox account, you could maintain control of storage.

You can set files to be accessible for reading by the public, but update or deletion only by you or by others you grant privilege to, such as forum moderators.

(th)

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