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#26 2019-09-08 18:13:22

tahanson43206
Member
Registered: 2018-04-27
Posts: 1,677

Re: Aldrin Cyclers and Asteroid Belt Cyclers

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)

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#27 2019-09-08 18:14:56

RobertDyck
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From: Winnipeg, Canada
Registered: 2002-08-20
Posts: 5,862
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Re: Aldrin Cyclers and Asteroid Belt Cyclers

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.

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#28 2019-09-08 19:02:55

kbd512
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Posts: 3,124

Re: Aldrin Cyclers and Asteroid Belt Cyclers

Robert,

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

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#29 2019-09-08 19:37:35

tahanson43206
Member
Registered: 2018-04-27
Posts: 1,677

Re: Aldrin Cyclers and Asteroid Belt Cyclers

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)

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#30 2019-09-08 20:26:19

RobertDyck
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From: Winnipeg, Canada
Registered: 2002-08-20
Posts: 5,862
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Re: Aldrin Cyclers and Asteroid Belt Cyclers

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.

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#31 2019-09-08 20:29:06

SpaceNut
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From: New Hampshire
Registered: 2004-07-22
Posts: 17,471

Re: Aldrin Cyclers and Asteroid Belt Cyclers

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

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#32 2019-09-09 20:11:53

tahanson43206
Member
Registered: 2018-04-27
Posts: 1,677

Re: Aldrin Cyclers and Asteroid Belt Cyclers

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)

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#33 2019-09-09 22:18:25

SpaceNut
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From: New Hampshire
Registered: 2004-07-22
Posts: 17,471

Re: Aldrin Cyclers and Asteroid Belt Cyclers

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.

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#34 2019-09-10 08:10:30

tahanson43206
Member
Registered: 2018-04-27
Posts: 1,677

Re: Aldrin Cyclers and Asteroid Belt Cyclers

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)

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#35 2019-09-10 17:16:38

SpaceNut
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From: New Hampshire
Registered: 2004-07-22
Posts: 17,471

Re: Aldrin Cyclers and Asteroid Belt Cyclers

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

220px-Animation_of_SpaceX_Roadster_trajectory.gif

Animation of SpaceX Roadster's trajectory.

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