Interstellar Transit Times using Maneuver Drive?
- Thread starter R_Kane
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S
Sophiathegreen
Guest
It depence on how close the drive can get you to the speed of light. At near light speed with time to accerate and deaccerate about 5 to 6 year.
Sir,
Sophia's estimate is fair enough ballpark estimate, the maths get rather hairy once you reach an appreciable fraction of c. Relativity rears quite an ugly head indeed. Time outside the ship and inside the ship become two very different things and your passengers will have some clock adjusting to do upon arrival.
Another point to consider is fuel. While thruster plates only require electricity, you still need to generate that juice for the length of the trip.
Sincerely,
Larsen
Sophia's estimate is fair enough ballpark estimate, the maths get rather hairy once you reach an appreciable fraction of c. Relativity rears quite an ugly head indeed. Time outside the ship and inside the ship become two very different things and your passengers will have some clock adjusting to do upon arrival.
Another point to consider is fuel. While thruster plates only require electricity, you still need to generate that juice for the length of the trip.
Sincerely,
Larsen
Sir,
I dug out my notes and fired up the old calculator.
Assuming 1 gee acceleration and a one parsec (3.23ly) trip distance, you're looking at ~750 days ship time and ~1480 days 'outside' time. That's a little over 2 subjective years for the crew while the people on either end of the voyage watch a little over 4 years pass.
This also assumes a constant acceleration - deceleration thrust profile, i.e. no coasting.
Relativity enters the picture at around 2/5ths of c.
Sincerely,
Larsen
I dug out my notes and fired up the old calculator.
Assuming 1 gee acceleration and a one parsec (3.23ly) trip distance, you're looking at ~750 days ship time and ~1480 days 'outside' time. That's a little over 2 subjective years for the crew while the people on either end of the voyage watch a little over 4 years pass.
This also assumes a constant acceleration - deceleration thrust profile, i.e. no coasting.
Relativity enters the picture at around 2/5ths of c.
Sincerely,
Larsen
daryen
SOC-14 1K
Larsen,
How about a more reasonable scenario:
An initial burst of thrust (could be big, at least a day, if not a week long), coasting for most of the journey (since everyone has retired to low berths at this point), the appropriate deceleration at the destination.
How long would that take?
How about a more reasonable scenario:
An initial burst of thrust (could be big, at least a day, if not a week long), coasting for most of the journey (since everyone has retired to low berths at this point), the appropriate deceleration at the destination.
How long would that take?
S
Sophiathegreen
Guest
Also I took in account the time need and distace needed to accelrate up to light speed which you can get to but give than fair estin of what getting to near light speed need. You will need 1 year time at than constant 1 g thrust and you will travel about than 1/2 light year in that time of acceration. If you only accerate for 1 week at 1 g you will need ten's of thousand of years or more to travel at that speed. You must also take in account outside forces and the fact there is than very thin amount of gases in space may-be 1 moleculate of h2 per cublic centimeter which can slow drown the ship.
"How about a more reasonable scenario:
An initial burst of thrust (could be big, at least a day, if not a week long), coasting for most of the journey (since everyone has retired to low berths at this point), the appropriate deceleration at the destination."
Sir,
Well, as long as you stay below 2/5ths of c and thus away from any relativity problems it would be a simple time-acceleration-distance problem.
Let's see, pull out the back of that envelope...
- Figure 1 gee (that's 0.0098km/sec^2) thrust for 2 weeks (that's 1209600 seconds) to reach a velocity of 11854.08km/sec.
- During that 2 weeks you'll have travelled 7,169,347,584 km. Remember that, it's the distance we'll need to slow down too.
- A light year is roughly 624,388,608,000 km. We'll have already travelled that distance above, plus we'll need to slow down, so subtract that twice from the distance we need to go. We'll end up with 610049912832 km left. Now just divide our velocity into that for a 'coasting' trip time of ~595.64 days. Don't forget to add the 28 days spent accelerating and decelerating. We end up with a total ~623.64 days most of which was spent at ~0.04 of c. (We don't need fear relativity until we near ~0.4 of c).
Sincerely,
Larsen
An initial burst of thrust (could be big, at least a day, if not a week long), coasting for most of the journey (since everyone has retired to low berths at this point), the appropriate deceleration at the destination."
Sir,
Well, as long as you stay below 2/5ths of c and thus away from any relativity problems it would be a simple time-acceleration-distance problem.
Let's see, pull out the back of that envelope...
- Figure 1 gee (that's 0.0098km/sec^2) thrust for 2 weeks (that's 1209600 seconds) to reach a velocity of 11854.08km/sec.
- During that 2 weeks you'll have travelled 7,169,347,584 km. Remember that, it's the distance we'll need to slow down too.
- A light year is roughly 624,388,608,000 km. We'll have already travelled that distance above, plus we'll need to slow down, so subtract that twice from the distance we need to go. We'll end up with 610049912832 km left. Now just divide our velocity into that for a 'coasting' trip time of ~595.64 days. Don't forget to add the 28 days spent accelerating and decelerating. We end up with a total ~623.64 days most of which was spent at ~0.04 of c. (We don't need fear relativity until we near ~0.4 of c).
Sincerely,
Larsen
"Also I took in account the time need and distace needed to accelrate up to light speed which you can get to but give than fair estin of what getting to near light speed need."
Sophia,
So did I.
"You will need 1 year time at than constant 1 g thrust and you will travel about than 1/2 light year in that time of acceration."
Did you remember to account for relativity? Without accounting for relativity, one year of thrust at one gee nets you a final velocity of ~308418 km/sec. Unfortunately, that is faster than the velocity of light at 297600 km/sec.
"If you only accerate for 1 week at 1 g you will need ten's of thousand of years or more to travel at that speed."
Sorry, no. Your math is off. Look at my post above for a 1gee/2 week thrust profile, you can traverse 1ly in a little less than 2 years.
"You must also take in account outside forces and the fact there is than very thin amount of gases in space may-be 1 moleculate of h2 per cublic centimeter which can slow drown the ship."
This bit is correct. At appreciable percentages of c, collisions with even the smallest of 'moleculates' could be catastrophic.
If I may be allowed a personal question, I noticed your occupation is listed as 'collect disabilities'. May I be so bold as to ask just what your disabilities are? A very dear friend of mine, Bari Stafford, passed away from ALS last summer. He enjoyed Traveller too and even managed to participate in the TML Ship Rodeo a few weeks before his passing.
Sincerely,
Larsen
Sophia,
So did I.
"You will need 1 year time at than constant 1 g thrust and you will travel about than 1/2 light year in that time of acceration."
Did you remember to account for relativity? Without accounting for relativity, one year of thrust at one gee nets you a final velocity of ~308418 km/sec. Unfortunately, that is faster than the velocity of light at 297600 km/sec.
"If you only accerate for 1 week at 1 g you will need ten's of thousand of years or more to travel at that speed."
Sorry, no. Your math is off. Look at my post above for a 1gee/2 week thrust profile, you can traverse 1ly in a little less than 2 years.
"You must also take in account outside forces and the fact there is than very thin amount of gases in space may-be 1 moleculate of h2 per cublic centimeter which can slow drown the ship."
This bit is correct. At appreciable percentages of c, collisions with even the smallest of 'moleculates' could be catastrophic.
If I may be allowed a personal question, I noticed your occupation is listed as 'collect disabilities'. May I be so bold as to ask just what your disabilities are? A very dear friend of mine, Bari Stafford, passed away from ALS last summer. He enjoyed Traveller too and even managed to participate in the TML Ship Rodeo a few weeks before his passing.
Sincerely,
Larsen
How much Hydrogen can a Traveller starship reasonable expect to carry in percentage terms. Normally a fusion rocket would be lucky to reach 1/10th of the speed of light and that is if it is a two staged fusion pulse rocket. (This is a 1 way acceleration, deceleration is achieved through a magnetic sail) In Traveller however we don't use rockets, and the starship's mass is not a consideration, only its volume. It takes just as much energy to accelerate a fully fueled starship as it does to accelerate a starship whose tanks are nearly empty. The thruster plates expend no reaction mass, so at the end of the journey the sublight starship is going to have fuel tanks full of liquid helium. So what is the theoretical maximum velocity of a Fusion powered (TL15 max)Traveller starship with a reasonable percentage of its volume devoted to fuel storage? You just have to divide the powerplants fuel consumption rate by the amount of fuel store to get its duration. Once you know how long it can accelerate, you can calculate its maximum speed using relativistic formulas. The formula to determine trip duration as measured on the starship is:
t'(1) - t'(0) = (c/a)inverse cosh(1 + (aS/c2))
t'(1) is the end time onboard ship (seconds)
t'(0) is the beginning time onboard ship (seconds)
c is the speed of light (299,792,458 m/s)
a is the ships acceleration in m/s (1-G = 9.8 m/s)
S is the distance traveled im meters
1 parsec = 3.26 light years
1 light year = 31,536,000 light seconds.
1 light year = 9.45 x 10^15 meters
1 parsec = 3.08 x 10^16 meters
There you have all the tools you need to calculate the relatavistic ship travel time to the end of its initial acceleration.
The formula for the ship's final velocity is:
V = c (1 - (1 / (1 + (aS/c^2))^2))^0.5
^ is the exponent operator.
once the cruise velocity is reached you use this formula for dertermine the travel time to cross the distance during cruise.
t' = (1 / (1 - (V^2/c^2))^0.5)) x (t - (Vx / c^2))
x is the distance crossed at constant velocity.
You then add the amount of time to accelerate as the time to decelerate and that is you total ship's time cruise for the sublight journey. To determine the travel time as perceived by the outside universe simply calculate the ship's average velocity as a percentage of the speed of light and divide the distance in light years by it. Remember to convert parsecs into light years.
For the vehicles
t'(1) - t'(0) = (c/a)inverse cosh(1 + (aS/c2))
t'(1) is the end time onboard ship (seconds)
t'(0) is the beginning time onboard ship (seconds)
c is the speed of light (299,792,458 m/s)
a is the ships acceleration in m/s (1-G = 9.8 m/s)
S is the distance traveled im meters
1 parsec = 3.26 light years
1 light year = 31,536,000 light seconds.
1 light year = 9.45 x 10^15 meters
1 parsec = 3.08 x 10^16 meters
There you have all the tools you need to calculate the relatavistic ship travel time to the end of its initial acceleration.
The formula for the ship's final velocity is:
V = c (1 - (1 / (1 + (aS/c^2))^2))^0.5
^ is the exponent operator.
once the cruise velocity is reached you use this formula for dertermine the travel time to cross the distance during cruise.
t' = (1 / (1 - (V^2/c^2))^0.5)) x (t - (Vx / c^2))
x is the distance crossed at constant velocity.
You then add the amount of time to accelerate as the time to decelerate and that is you total ship's time cruise for the sublight journey. To determine the travel time as perceived by the outside universe simply calculate the ship's average velocity as a percentage of the speed of light and divide the distance in light years by it. Remember to convert parsecs into light years.
For the vehicles
S
Sophiathegreen
Guest
Sorry I was thinking in term of our chemical rocket which are very limit in mass ratio. Most chemical rocket have than exhaust velocity at the most of 3 to
4 milies per second to reach any decent speed it will
need to have than big fuel tank which add dead weight
which limit it top velocity to about 2 time exhaust velocity unless you mult-stage. Any reaction engine will have the same problen except for photon rocket which have than exhaust velocity of the speed of light. Unless you use than interstellar ramship to bypass the mass ratio of initial mass/ final mass.
Most space chemical rocket are 80 to 90 % fuel by mass. Look at the size of the Saturn 5 rocket compare to the command modural and service modural.
that why our four space probe which are now traveling in interstellar space are going to take than long time to get anywhere. The fastest one has than velocity of 3.5 AU/year(325,500,000 miles in one year time. There is 63500 AU in one light year.
To get than faster than exhaust velocity you need than very hight mass ratio.
4 milies per second to reach any decent speed it will
need to have than big fuel tank which add dead weight
which limit it top velocity to about 2 time exhaust velocity unless you mult-stage. Any reaction engine will have the same problen except for photon rocket which have than exhaust velocity of the speed of light. Unless you use than interstellar ramship to bypass the mass ratio of initial mass/ final mass.
Most space chemical rocket are 80 to 90 % fuel by mass. Look at the size of the Saturn 5 rocket compare to the command modural and service modural.
that why our four space probe which are now traveling in interstellar space are going to take than long time to get anywhere. The fastest one has than velocity of 3.5 AU/year(325,500,000 miles in one year time. There is 63500 AU in one light year.
To get than faster than exhaust velocity you need than very hight mass ratio.
S
Sophiathegreen
Guest
If you are coasting you arenot acceration. It was 20 or 30 year since I have to remember rocketry formular. Alot of people think than single stage rocket would have gone to the moon and back not thinking of the amount of oxygen and fuel you need to carry.
