In a message dated 2/11/00 11:01:20 PM, IdahoBob writes:
<< This was forwarded to me, because someone guessed I could help.
From: ffml-bounce@fanfic.com [mailto:ffml-bounce@fanfic.com]On Behalf Of
Marohki@aol.com
Sent: Thursday, February 10, 2000 11:19 AM
To: ffml@fanfic.com
Subject: [FFML] [Query] BGC Mars?
Hey.. I'm hoping for some help here..
I've been working on and off during my free time on a BGCFic.. the prologue
requires that a Boomer operated spcecraft go to Mars and back..
My question:
Can anybody give me an estimate of travel time for a fusion engine powered
spacecraft with a boomer crew to and from Mars..?
Any help appreciated..
(Take notes, this will be on the final. <G>)
Ok, a minimum fuel trip from the Mars to Earth (or the other way
around) follows eccentric orbit that on the outside just touches Mars
orbit and on the inside just touchs Earth orbit. Earth orbit is one year,
Mars is about 2 years, so the the orbit would be an average, 1.5 years,
and .75 year (9 months) one way. If you look at the latest Mars landers
and stuff, that's about how long they take to get there.
It's also like taking the sailing ship route, when you want to talk
about a speedboat.
Mars Earth Ratio
(Mars/Earth)
Semimajor axis (10^6 km) 227.92 149.60 1.524
Distance from the Earth to Mars is as little as 78.32x10^6 km
(Sun-Earth-Mars) and is as great as 377.52 x 10^6 km (Earth-Sun-Mars).
The second one isn't quite true flight distance, because direct flight at
that path would acutally have to go thougth the sun... so it would be a
little longer.
Now if they accelerated constantly on the whole trip, the first half
would be boosting toward earth, and the second half would be braking. Now
lets leave out the fact that they have to match velocities, manuver, and
fight or go with the gravity of the sun.
distance = 1/2 acelleration * time^2
They would travel half the distance, then turn around and slow down.
Also the time from Mars to the turn around point should be the same as
the time from the turn around point to Earth. Moving this around and
solving for time gives...
time = 2 * sqr( distance / accelleration )
A little math, and conversion to meters gives this...
Distance (m) 78.3x10^9 377x10^9
Acceleration (m/s) 9.8 9.8
Acceleration (G's) 1 1
time (sec) 178771 392272
time (days) 2.069 4.540
Or about 3 1/2 days on ball park average. That is if you could run the
engines all the time. (Imagine stomping on the gas peddle of a big muscle
car, and watching the speedometer go up and up for two days, then slaming
on the breaks and having to stop for two days!)
Now boomers wouldn't be limited to just one G, so lets see more....
Distance (m) 78.3x10^9 377x10^9 78.3x10^9
377x10^9
Acceleration (m/s) 98 98 980 980
Acceleration (G's) 10 10 100 100
time (sec) 56532 124047 17877 39227
time (days) 0.654 1.435 0.206 0.454
So, at 10 G's (or more than the maximum that the Apollo Astronauts
felt on reentry, at Mach 36) it would be about a day, and at 100 G's
(about 5 or 6 times greater than the best human could endure without
dieing) it's less than a half a day.
I don't have the stuff here for fuel calulations, but I bet the 10 G
craft would have to be mostly fuel, even for fusion flight. The 100 G
probably would be 95% or 99% fuel to do it.
If I was writing a story, I'd use something like 5 G's (Could be
very impressave, without being way out there. Especially if you calulate
what the boomer weighs under that acceleration, 5 times his earth weight.
a 800lb boomer would crush down in his seat as if he was 2 tons!).
Distance (m) 78.3x10^9 377x10^9
Acceleration (m/s) 49 49
Acceleration (G's) 5 5
time (sec) 79948 175429
time (days) 0.925 2.030
(Ball park average = 1 1/2 days)
Now to end this all, after impressing you with formulas, numbers,
and big words, I haven't done stuff like this in 10 years and could be
way off base (or really screwed up in the math). So It's ok for a Fan
Fict, but I wouldn't want to use it to prove something..
Mark Philipp (aka: IdahoBob)
Mars Info got off of...
http://nssdc.gsfc.nasa.gov/planetary/factsheet/marsfact.html >>
I want to thank you and everybody for their help on this subject.. I got
quite an array of answers and eventually decided to go with a 6 week trip
simply for efficiency and neatness..
Some of the technical data will doubtless be useful for other projects as
well..
in reference to the admin comment about it needing to be private in the first
place..
Sorry there also, E-mailed it to the list so I could get a wide range of
opinions on the subject.. so as to get the broadest spectrum as possible..
and as I had seen other people making general list inquiries I did not
realize anything was wrong..
Thank you all again for your help, links, and opinions..
Till next time..
PS.. anyone having any additional comments can e-mail them to me privately..
Thank you again..