The Prophesy Chronicles - Discussion Thread

[TheBigDog]

The Prophesy is comprised of four major rings, each made of 120 sections. Between those rings are the habitation rings which are like the original ship and are shaped as a single long ring without apparent sections. The rotational speed generates G. There is a center section known as ZeroG, which is essentially that as it along the rotational axis. The rotation speed can be controlled to set the gforce of the living space from near zero to 2.5. Above 2.5 I think would be immensely difficult to be habitable, and you get to a question of engineering, and how much stress the ship can handle, including things like water pumping systems.

 

A generation before the should would enter the orbit of a planet a decision would already be made that the planet was habitable. There is not enough fuel to stop and check one out and then move on again, so surveys are done during approach to decide if this is the place we are stopping or if we are using this star system to maneuver to the next via slingshot.

 

Once the decision is made to stop the ship is transformed to match the physical conditions of the chosen planet, primarily G force of the living section. The four main rings contain agriculture. Initially one of them is transformed to match the environmental conditions of the planet to begin adapting plants and animals which will be used for the settlement. There will be some 20 years to get this right, perhaps 40 before settling into orbit. Once in orbit the ship can linger almost indefinitely before dropping landing pods filled with people, equipment, plants, animals, and hope. So if it takes 10 generations to adapt to a 2G environment then so be it. If it takes 20 generations, fine. As long as the crew can be patient, the ship can keep them. Of course the closer the conditions of the planet are to earth the easier the assimilation process.

 

I also see the Prophesy as more than a one stop shop. The ship will remain in orbit above the settled planet. The landing pods will be used as shelter until permanent settlements can be made. One of the goals of the settlement will be to build technology and industry to the point that they can launch the pods (or new pods) back up to the Prophesy, refuel her, and send her off on the identical mission again. Over two thousand years she may be used to settle three or four planets. Some people may elect to stay on the ship rather than settle on the planet. Who knows, the Prophesy could eventually return to earth thousands of years later manned by the descendants of the original crew after having settled a dozen or more planets. She could find earth on the dark side of a planetary cataclysm and start a new colony here. It is worth noting that each colony will have the technology to duplicate the Prophesy, and the tradition of planetary settlement. It may be that five thousand years later there are two dozen ships like her, better than her, branching out through the galaxy finding planets to settle.

 

It makes you wonder about the validity of the Drake Equation.

 

Bill

[TheBigDog]

I have been doing some thinking about time, and the question of "What time is it?" from the frame of reference of the characters on the Prophesy. There is a nice accurate clock on board that gives them the correct time as it is passing in their frame of reference.

 

The first story takes place about 71 years after leaving orbit. The ship takes some time building speed inside our solar system through a complex series of gravity slingshots before leaving on a beeline for Proxima Centauri at a velocity of about 6 AU/day. This gives about 123 years to reach Proxima Centauri where the ship will then use that three star system to maneuver toward the target system at even greater velocity. Because of the eccentric flight path, and the high velocity it becomes a complex issue to know exactly the time frame of communications with earth. To that end the crew has several date/time references to consider. At the time of this story the ship is about 2.4 light years from Earth.

 

ST: Ship Time. This is the time experienced on the ship by the crew and serves as local time. It started as the same time as the launch center off the shore of Panama. It is the real clock on the ship. All other times are adjusted for SR based on this clock's reading and an understanding of the motion of the ship.

 

ET: Earth Time. This shows the equivalent "simultaneous time" at the launch center on earth. This clock is moving slightly faster, and SR is used to determine what that clock will indicate versus ST.

 

ETER: Earth Time Earth Receipt. There is a clock that shows the earth date that a radio transmission will reach earth if made at that moment form the ship.

 

STER: Ship Time Earth Receipt. There is a clock that shows the Prophesy date that a radio transmission will reach earth if made at this moment from the ship.

 

ETET: Earth Time Earth Transmit. There is a clock that shows the earth date that radio transmission being received right now was made.

 

STET: There is a clock that shows the Prophesy date that radio transmissions being received right now was made.

 

ETP: Earth Time Ping. There is a clock that shows the earth date that a radio transmission made right now from earth will be received by the Prophesy, answered when received and the answer then received by the earth.

 

STP: Ship Time Ping. There is a clock that shows the Prophesy date that a radio transmission made right now from the Prophesy will reach earth, be answered when received, and the answer then reach the Prophesy.

 

All of these times are validated by timestamps in the digital messages sent between Earth and the Prophesy.

 

Since the flightpath of the ship is very well understood, the computer handles keeping track of all the clocks based upon what the actual future position of the ship will be. In the 4.8 years that radio signals take to ping off the earth the ship will have traveled a large distance. While using the tri star Centauri system for gaining more velocity and aiming at the target system they will actually close the gap with Earth on one leg before moving off at another angle. All of this comes into play in how the different times are calculated at any given moment.

 

If I am on the ship, and I receive a message from Earth, this information will help me understand which ship transmissions have already been received and which ones have not yet. I am also thinking that all transmissions will have two serial numbers encoded. One is the next number from the transmit side, and the other is the last number received. This would keep an absolute reference but would indicate a single stream of communication each direction. Since all communications are digital, there would be a database at each end which kept a database log of all inbound and outbound messages.

 

This will be talked about in background in the story. I wanted to present it here to get feedback on the concept, and to see if I was missing anything critical.

 

Thanks!

 

Bill

[Jay-qu]

I havent got much time right now, but it seems this would be a useful tool at this point (see attached). It calculates the ship and earth time taken to get to the destination for given velocities. It takes a while for time dilation to really kick in.

[TheBigDog]

Thanks for the file JQ! I used the following values...

 

Velocity of the Prophesy = 10,388,741 meters/second

Speed of Light = 299,792,458 meters/second

 

Velocity = 3.46% speed of light

 

Time dilation effect = 51.89 seconds/day. Every 27 minutes and 45 seconds the earth clock moves one second more than the ship clock. Over 123 years that adds up to the ship being 27 days younger than it would be if it had stayed in Earth orbit. Not significant for a lifetime, but significant for communications purposes.

 

Bill

[JoeRoccoCassara]

If evolution and natural selection allow a human to thrive under high-pressures, then what would we look like physically compared to your average earth-ling. Would anyone be fat? What about the women?

[TheBigDog]

I am working on the first installment for the Chronicles thread. Don't be fooled by a couple days of apparent inactivity.

 

Bill

A couple days of inactivity... right.

 

Not a day passes that I do not work on the puzzle of the Prophesy in my mind. But few are the days where I write anything down. I have thrown away more than I have left, which is back-assward., but that is what it is.

 

So... I have a question of the technical type.

 

How far from Earth could the Prophesy be and still have communications? It is not just a matter of delay when you are light years away, it is a matter of hearing the signals. How far could signals be transmitted and heard? Would the fact that both the earth and the ship would be moving targets have a bearing on it? If I send an aimed, amplified signal to the earth, I need to aim it where the earth will be when the signal arrives. Likewise the earth would need to aim at where the Prophesy will be. If the ship were to change course 5 light years from earth they would risk missing 10 years of messages.

 

I think about radio signals coming from the earth going into space. I think about how insignificant they are compared to the energy being emitted by the sun. Yet the light and energy from the sun becomes virtually indistinguishable at a far enough distance. With all the resources of a planet, or on the most advances space ship possible, would there be enough energy to make yourself heard across the vast stretch of space between stars?

 

Bill

[CraigD]

How far from Earth could the Prophesy be and still have communications? It is not just a matter of delay when you are light years away, it is a matter of hearing the signals. How far could signals be transmitted and heard?

The detailed work to answer this question is, alas, a bit over my out-of-practice skills at present, but thanks to google and decent search phrase intuition, I found this “SETI range calculator”, from a commercial satellite communication company. Using its defaults gives a result of a usable 10.701 GHz signal detected by a 50 m diameter dish near Earth at a range of about 4.6 light years for a 10 m transmitter dish with a modest 60 KW power. Doubling power increase range by [imath]\sqrt2[/imath]. Doubling dish diameter doubles range. The range for the 50 m Earth dish sending at the same frequency and power to the 10 m ship dish is the same.

 

From this, and I don’t think Earth-Prophesy communication would be an issue. The Prophesy is a big, high-power ship, so could have lots of big, high-power, but not terribly narrow-beam radio dishes.

Would the fact that both the earth and the ship would be moving targets have a bearing on it? If I send an aimed, amplified signal to the earth, I need to aim it where the earth will be when the signal arrives. ...

‘Cause radio dishes aren’t very narrow-beam, I don’t think this would be a problem.

[TheBigDog]

The detailed work to answer this question is, alas, a bit over my out-of-practice skills at present, but thanks to google and decent search phrase intuition, I found this “SETI range calculator”, from a commercial satellite communication company. Using its defaults gives a result of a usable 10.701 GHz signal detected by a 50 m diameter dish near Earth at a range of about 4.6 light years for a 10 m transmitter dish with a modest 60 KW power. Doubling power increase range by [imath]\sqrt2[/imath]. Doubling dish diameter doubles range. The range for the 50 m Earth dish sending at the same frequency and power to the 10 m ship dish is the same.

 

From this, and I don’t think Earth-Prophesy communication would be an issue. The Prophesy is a big, high-power ship, so could have lots of big, high-power, but not terribly narrow-beam radio dishes.

 

‘Cause radio dishes aren’t very narrow-beam, I don’t think this would be a problem.

Thanks Craig. That simplifies it for me. The only problem is the long delay and some sporadic problems due to literary license. ;)

Bill

[Jay-qu]

I hope you are keeping your eyes on the Gliese 581 system, astronomers just found another Earth-ish sized planet that is in the habitable zone :)

http://news.discovery.com/space/earth-like-planet-life.html

[TheBigDog]

I hope you are keeping your eyes on the Gliese 581 system, astronomers just found another Earth-ish sized planet that is in the habitable zone :)

http://news.discovery.com/space/earth-like-planet-life.html

Cool news indeed, JQ!

[TheBigDog]

OK,we have a 20 billion kg ship in LEO. We want to accelerate to 3.456% of light speed. If we plan of taking 200 years to get to that speed it will take a constant thrust of 33,000,000 newtons. That is an awful lot of thrust for an awful long time. The acceleration rate would be very very very slow. My question is this...

 

It the ship in LEO is on the same plane as the moon would it be accelerating fast enough to avoid hitting the moon? It seems that it would not fly straight away, but would go into an increasingly eccentric orbit until the apogee was at an escape point. Or would it simply spiral into an ever increasing radius. Either way, is there a minimum acceleration required to escape the earth without hitting the moon?

 

Bill