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#1 2004-12-11 12:40:12

John Creighton
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From: Nova Scotia, Canada
Registered: 2001-09-04
Posts: 2,401
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Re: Why not a cycler?

[color=#000000:post_uid0]Just make the cycle the size of a normal ITV. Doc with it in a nuclear safe orbit. Fire nuclear thermal engines to put it into trans Mars injection put some ion thrusters on it to help keep it on the same trajectory. In about five years you are more or less aligned for another trip from earth to mars. Unfortunately by year 10 it looks bad but I assume in five more years you have another partial alignment and five years after that you have a good alignment five years after that you have a partial alignment and five years after that you have a bad alignment. I am concluding this from plots generated by the following code(figures to come).

[code:1:post_uid0]%MATLAB CODE to visulize a cycler
PE=(2/2)^(3/2)                  %The period of the Earth in Years
PM=(2*1.75/2)^(3/2)        %The period of Mars in Years
PC=((1+1.75)/2)^(3/2)      %The period of the cycler in years
t=linspace(0,10,1000);
 
 
ex=cos(2*pi/PE*(t));        %The cosine of the angular postion of the earth
ey=sin(2*pi/PE*(t));        %The sine of the angular postion of the Earth

mx=cos(2*pi/PM*(t+(PM-PC)/2)); %The cosine of the angular postion of mars
my=sin(2*pi/PM*(t+(PM-PC)/2)); %The sine of the angular postion of mars

cx=cos(2*pi/PC*(t));                %The cosine of the angular postion of the cycler
cy=sin(2*pi/PC*(t));                 %The sine of the angular postion of the cycler


%Plot the sine and the cosine of the angle for earth mars and the cycler. The
%cycler intersects earth when the cosine is equal to one and the sine is equal to zero
%The cycler intersects mars when the cosine is equal to negative one and the sine is qual to zero

subplot(2,1,1);
plot(t,ex,'b',t,mx,'r',t,cx,'k');
subplot(2,1,2)
plot(t,ey,'b',t,my,'r',t,cy,'k');[/code:1:post_uid0]

The code was for an outbound trip using a hofmann transfer. You would need to launch another ship for the return flight. To hofmann transfers and you have roughly one flight every seven years.[/color:post_uid0]

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#2 2004-12-11 12:46:55

John Creighton
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From: Nova Scotia, Canada
Registered: 2001-09-04
Posts: 2,401
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Re: Why not a cycler?

[color=#000000:post_uid0]I see a potential pitfall. If a cycler is used then its course will not be directed towards the Martian atmosphere. This would mean a maneuver would have to be done to approach the Martian atmosphere.  The later this maneuver is done the more delta V it will require but the earlier it is done the less time a crew gets to enjoy on the cycler.[/color:post_uid0]

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#3 2004-12-11 13:54:15

John Creighton
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From: Nova Scotia, Canada
Registered: 2001-09-04
Posts: 2,401
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Re: Why not a cycler?

[color=#000000:post_uid0]From post

More:

http://www.geocities.com/zlipano....26.html

Look at that map! Land on 1998 KY26 and hop off closer to Mars!

Cool! [/quote:post_uid0]

I wonder how hard it would be to make the trajectory of this asteroid closer to a hofmann trajectory. It is already pretty close.
Carbon and Asteroid Prospectors[/color:post_uid0]

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#4 2004-12-11 13:58:36

John Creighton
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From: Nova Scotia, Canada
Registered: 2001-09-04
Posts: 2,401
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Re: Why not a cycler?

[color=#000000:post_uid0]

There are cycler orbits that regularly fly both Earth and Mars. Buzz Aldrin has designed one that passes by both Earth and Mars each synodic period (about 2 & 1/7 years). The "castle" would be be well stocked with radiation shielding, food, air (maybe even self sustaining closed ecology life support systems). Then when the castle is in the neighborhood of either Earth or Mars a much less massive "taxi" can be sent to the planet (or from the planet to the castle). However Aldrin cyclers demand a lot of delta vee from their taxis since it passes Mars with a relative velocity of about 12 km a second.

Then there are two types of cyclers that pass by the planets somewhat less frequently but still regularly. Niehoff VISIT 3  passes by the earth every 3 years and Mars every 7.5 years. Niehoff VISIT 1 earth every 5 years and Mars 3.75 years.

I talk about nudging asteroids into Niehoff cycler orbits on this page:
http://www.clowder.net/hop/railroad/sched.html

[/quote:post_uid0]

This is very interesting but I wonder if it would be better to have a cycler that passes less frequently but requires less delta V. As I said for each mission launch one cycle on a hohmann to mars and on scheduled to return from mars on a hohmann. Eventually there will be enough cyclers hohmann trajectories that you won’t need a new cycler/ITV for each mission. You only need one to rendezvous with it on mars and another one to rendezvous with it on earth.[/color:post_uid0]

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#5 2004-12-11 16:00:46

John Creighton
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From: Nova Scotia, Canada
Registered: 2001-09-04
Posts: 2,401
Website

Re: Why not a cycler?

[color=#000000:post_uid0]I placed some cycler plots here:

http://s243a.trap17.com/cycler1.htm
There are 3 plots that cover 30 years for a hofmann transfer. Here they are.
[img:post_uid0]http://s243a.trap17.com/cycler1_files/image001.jpg[/img:post_uid0]

Looking at the plot if the cycler had a period of 3/2 years it would be pretty close to a hohmann transfer and it would arive at earth every three years.[/color:post_uid0]

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#6 2004-12-12 11:36:23

John Creighton
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From: Nova Scotia, Canada
Registered: 2001-09-04
Posts: 2,401
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Re: Why not a cycler?

[color=#000000:post_uid0]Anyway to explain the graph further the top graph is the cosine of the angle the bottom graph is the sine of the angle. The cycler leaves earth at year zero, the cosine of the angle is 1 and the sine of the angle is zero. Then in about 0.8 years the cycler arrives at mars where the cosine of the angle is -1 and the sine of the angle is zero. Notice on year 5 (in 6 years) the cycler is roughly back to where it started. It would not take much thrust over 6 years with say an ion engine to provide enough course correction to make the cycler line up for another hofmann trajectory after 6 years. To asses the value of this we must consider the time value of money. What ever it would cost to build a new ship after 6 years we must move that value backward in time to see how much initial investment in dollars would be required to accumulate that much money. A rough but not exact approximation would be to subtract 10% a year. For an exact formula look in any engineering economics text book. Now NASA reference mission has three launches anyway. So if on vehicle was launched from earth to go to mars at the right time and one was launched to return from mars at the right time and you used a reusable MAV (I know GCNRevenger won’t like that idea) then you use the same number of vehicles anyway. Moreover you do need needed fuel to speed up or slow down the ITV/circler. The only additional cost is the electric propulsion needed to position the cycler in the to the correct transfer orbit 6 years after leaving earth and 5.2 years after leaving mars.[/color:post_uid0]

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#7 2004-12-12 19:54:39

RobS
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From: South Bend, IN
Registered: 2002-01-15
Posts: 1,701
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Re: Why not a cycler?

[color=#000000:post_uid0]Two big problems with cyclers that time might solve:

1. You have to leave Earth or Mars orbit at exactly the right second or miss the launch window entirely. This problem will go away after maybe a dozen or so launches when everyone has experience and the equipment is well known.

2. The bigger problem: You're creating a very big, expensive machine (because you want it spacious and well shielded), using it only once every few years for a few months (a huge waste), and you're counting on it not to break down the 90% of the time no one is on board.

           -- RobS[/color:post_uid0]

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#8 2004-12-12 21:21:51

SpaceNut
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From: New Hampshire
Registered: 2004-07-22
Posts: 19,729

Re: Why not a cycler?

[color=#000000:post_uid14]I would propose not a single unit but since it is on a 3/2 resonance, why not make it 3 vehicles launched so that they have a few months in orbit around mars and each brings a fresh crew from Earth on each pass out to mars. Basically creating a 2 year cycle of crews for round trip or a 2 year cycle on the surface. Either way it keeps a fresh crew and supplies always in route.[/color:post_uid14]

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#9 2004-12-13 09:14:07

John Creighton
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From: Nova Scotia, Canada
Registered: 2001-09-04
Posts: 2,401
Website

Re: Why not a cycler?

[color=#000000:post_uid0]

1. You have to leave Earth or Mars orbit at exactly the right second or miss the launch window entirely. This problem will go away after maybe a dozen or so launches when everyone has experience and the equipment is well known.[/quote:post_uid0]

Maybe true. I’ll try to figure out the launch window later for a given delta V and trait time constraint.

2. The bigger problem: You're creating a very big, expensive machine (because you want it spacious and well shielded), using it only once every few years for a few months (a huge waste), and you're counting on it not to break down the 90% of the time no one is on board.[/quote:post_uid0]

If it is alright to go to mars with a craft that is not overly spacious and well shielded then it is alright to go in a cycle that is not overly spacious and well shielded. The advantage of the cycler is you do not need a circulizating burn and you can reuse it. Thus it becomes possible to make it more massive. As for how long it will last without breaking down, there are deep space probes that run for decades. What is it about life support systems that makes them break down quicker and what can we do to increase there longevity. As for the size of the cycler I suggest one or two biggalo hotels. Each one should have there own life support system so if one fails there is a back up. Each one should have four docking modals that can be docked to another hotel or a engine to push it or a space ship. This way it should be possible to increase the space of the cycler over the years if desired. One difficult of increasing the space in the cycler is it will require more thrust to keep the cycler on the same orbit. I see a problem with just staking engines side be side because there radiators might get in each others way and heat dissipation might become a problem.[/color:post_uid0]

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#10 2004-12-13 09:22:44

John Creighton
Member
From: Nova Scotia, Canada
Registered: 2001-09-04
Posts: 2,401
Website

Re: Why not a cycler?

[color=#000000:post_uid0]

I would propose not a single unit but since it is on a 3/2 resonance, why not make it 3 vehicles launched so that they have a few months in orbit around mars and each brings a fresh crew from Earth on each pass out to mars. Basically creating a 2 year cycle of crews for round trip or a 2 year cycle on the surface. Either way it keeps a fresh crew and supplies always in route.[/qutoe]

I agree that it would be more desirable to have a more continuous flow. You would need 3 vehicles in a hofmann trajectory if you were only concerned about going to mars. You would need 6 vehicles if you want a return flight. My point is if you can build a cycler without to much extra cost then a normal interplanetary transfer vehicle or trans mars injection vehicle then you will save money on your next flight in six years time. If you build three all the better. What would be the maxium continuous rate for Hofmann trajectories (every nine moths?) .[/color:post_uid0]

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#11 2004-12-13 09:37:06

John Creighton
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From: Nova Scotia, Canada
Registered: 2001-09-04
Posts: 2,401
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Re: Why not a cycler?

[color=#000000:post_uid0]I noticed a discrepancy between the transfer times given by the Mars academy
[img:post_uid0]http://www.marsacademy.com/eq12.gif[/img:post_uid0]


and those given by wikipedia.


The formula at wikipedia rings a bell from a classical mechanics course so I think they are right. Also there formula above it on the mars academy website looks right so it must be a transcription error.
[img:post_uid0]http://www.marsacademy.com/eq11.gif[/img:post_uid0]


I tried to send them an email to inform the mars academy of their mistake but the adress given no loner accepts emals . By the way in my above figure I used the wikipedia formula.

I’m curious as to why wikipedia puts the units of the standard gravitational parameter in km/s^2 as opposed to AU/year^2 or AU/month^2.[/color:post_uid0]

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#12 2004-12-15 06:07:27

mboeller
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From: germany
Registered: 2004-05-08
Posts: 53

Re: Why not a cycler?

[color=#000000:post_uid0]Maybe you will find this NIAC study useful :

http://www.gaerospace.com/projects/Astr … otels.html[/color:post_uid0]

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#13 2004-12-15 11:58:46

John Creighton
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From: Nova Scotia, Canada
Registered: 2001-09-04
Posts: 2,401
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Re: Why not a cycler?

[color=#000000:post_uid0]

Maybe you will find this NIAC study useful :

http://www.gaerospace.com/projects/Astr … otels.html [/quote:post_uid0]

Sounds interesting smile.

I started reading this and I think a lot of people are thinking on the same lines. The choose a 70 ton vehicle. Sounds reasonable. Solar electric for course correction using liquid oxygen as fuel. Obvious smile. Hyperbolic transfer on taxi? Maybe, I have to study it further. I guess it is need to get to the cycler in a week. I think they make a convincing case. Must read more.  They choose a 6 month transfer instead of a slightly slower hofmann transfer. Maybe that is the way to go. I would like to explore both possibilities.

[b:post_uid0] edit: I think the hyperbolic transfer orbit for that taxi may be with respect to the earth and not the sun. Maybe?  ??? [/b:post_uid0][/color:post_uid0]

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#14 2004-12-15 12:06:19

John Creighton
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From: Nova Scotia, Canada
Registered: 2001-09-04
Posts: 2,401
Website

Re: Why not a cycler?

[color=#000000:post_uid0]

I would propose not a single unit but since it is on a 3/2 resonance, why not make it 3 vehicles launched so that they have a few months in orbit around mars and each brings a fresh crew from Earth on each pass out to mars. Basically creating a 2 year cycle of crews for round trip or a 2 year cycle on the surface. Either way it keeps a fresh crew and supplies always in route. [/quote:post_uid0]

Let me make a slight correction here. For a 3/2 period you could use the same vehicle both ways. However, on the outgoing flight it would take you 1.5/2 years and the return flight would take you 4.5/2 years. That is quite a while to be on a space craft. However, perhaps this could be reasonable if a smaller crew went on the return flight. The would need less rations and could perform some maintenance.  So you would have two flight options the quick flight and the slow economy class. However is someone is going to be in orbit for 4.5/2 years the cycler will need artificial gravity and more shielding. On the plus side this will make the fast flights that much better. I think the people on the slow flight might be put to work processing asteroids for science and industry.[/color:post_uid0]

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#15 2004-12-15 12:19:42

John Creighton
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From: Nova Scotia, Canada
Registered: 2001-09-04
Posts: 2,401
Website

Re: Why not a cycler?

[color=#000000:post_uid0]From http://www.gaerospace.com/projects/Astr … otels.html

Cycler orbits between Earth and Mars that enable fast, frequent transfers between these planets
Small, human transport space ships, or Astrotels, on cycling orbits between planets,
Orbital Spaceports at the planets
Very small, fast, hyperbolic transfer vehicles, or Taxis, between Spaceports and Astrotels.
Propellant and life support in situ resource manufacturing plants
Cargo vehicles that utilize low-energy, long-flighttime orbits to transport propellant and low value cargo to and from planets
Shuttles to and from Spaceports and planetary surfaces [/quote:post_uid0]

I wonder if the space ports are necessary and if they are if ISS could be used as one. One bit of optimize I have is the space ports don't have to be as big as ISS. I would think one or two bigalo hotels (A.K.A trans hab modules) would do just fine.[/color:post_uid0]

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#16 2004-12-17 00:21:03

Hop
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From: Ajo
Registered: 2004-04-19
Posts: 146
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Re: Why not a cycler?

[color=#000000:post_uid0]Let me make a slight correction here. For a 3/2 period you could use the same vehicle both ways. However, on the outgoing flight it would take you 1.5/2 years and the return flight would take you 4.5/2 years. That is quite a while to be on a space craft. However, perhaps this could be reasonable if a smaller crew went on the return flight. The would need less rations and could perform some maintenance.  So you would have two flight options the quick flight and the slow economy class. However is someone is going to be in orbit for 4.5/2 years the cycler will need artificial gravity and more shielding. On the plus side this will make the fast flights that much better. I think the people on the slow flight might be put to work processing asteroids for science and industry.[/color:post_uid0][/quote:post_uid0]
[color=#000000:post_uid0]I have been fired up about the 1.5 year cyclers for some time (aka the Niehoff VISIT 2 cycler). You are reaching the same conclusions I have that it could visit both Earth and Mars repeatedly. As you note, the delta vee isn't much more than Hohmann transfer orbit.

If the cycler is an asteroid nudged into the cycler orbit, folks on this slow flight could indeed be put to work for science and industry. It's believed asteroids and comets are much less changed since the solar system's formation than planet surfaces. They are of great scientific interest. Also many have very pure metals and some have water and carbon compounds.[/color:post_uid0]


Hop's Orbital Mechanics Coloring Book - For kids from kindergarten to college.

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#17 2004-12-17 11:32:52

John Creighton
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From: Nova Scotia, Canada
Registered: 2001-09-04
Posts: 2,401
Website

Re: Why not a cycler?

[color=#000000:post_uid0]I am warm cold about using an asteroid as a cycler. It would provide easier resources to use.
However, if you want to expand the cycler you have to impalement the changing shape of the
asteroid into the changing shape of the cycler design. Moreover the asteroid is massive and it
may not be reasonable to correct the orbit enough with electric population to use. Consequently it
might be a hit or miss trip schedule. If you had a cycler on roughly 3/2 period the corrected its
course so it always hit mars exactly every 6 years then its orbit would slowly rotate and one
cycler could visit many asteroids over the years. Perhaps it would be better to export rocks to the
cycler from the asteroid that closely match its orbit at any give time then trying to make a cycler
out of an asteroid.[/color:post_uid0]

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