8.5 Galatic days plus more?

Abub's picture
Abub
November 18, 2014 - 10:28am
So now I know it's up to the narrative and all but I'm wondering about the time it takes to get from planet to planet assuming a void jump in between. 

8.5 galactic days is about the time it takes to speed up to 1% light speed and then slow down again at 1g. That is the time estimate I have now used a few times for my players to get from place to place. 

But that sort assumes that the astrogation was pinpoint calculated from starting point to planet and not starting point to star. 

If it was able to pinpoint it to the planet itself (somehow seeing its location in its orbit) then the ship would scream through a system at an astronomical (is that a pun?) speed. It could easily hit things like asteroid belts and other planets/planetiods (*pours one out for fallen Pluto*)

So. I'm wondering should I start assuming a void jump should be slowing to some kind of "cruising speed" just outside the target star's heliosphere?  What would be a safe cruising speed for zipping around in a system. Since this isn't star trek a craft flying at a high speed is just not able to turn. Yes space is very empty I know but at what speeds would they be in danger of not being able to turn?

I've been poking around the web to try and figure out the distance traveled during the constant acc/deceleration to/from 1% light speed but haven't found one yet that doesn't involve me relearning calculus. Any of yinz worked that out yet?
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Comments:

Shadow Shack's picture
Shadow Shack
November 18, 2014 - 12:14pm
AD spells it out at one day per light year, and KH sticks with that as well.

Technically at ADF:5 one could reach jump velocity in 200 ten minute turns, but the astrogation time required far outweighs any ship's ability to reach jump velocity.
I'm not overly fond of Zeb's Guide...nor do I have any qualms stating why. Tongue out

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Abub's picture
Abub
November 18, 2014 - 12:57pm
that and the crew would all pass out from that.

Sooo... 1 galactic day per light year... that doesn't work when you put the rubber to the road since the time spent getting to 1% and back down is a constant and the distance only changes how many seconds you spend in the void.

Not saying that isn't what AD says... it just is a simplification that doesn't work.

I'm still working on the distance you need to travel accelerating at +/- one g to determine if that minimum distance is likely greater then the number of AUs of a system's heliosphere.

Our Heliosphere is about 122 AUs with 80 AUs being where interstellar medium slows the solar winds down to subsonic speeds.



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Abub's picture
Abub
November 18, 2014 - 1:23pm
So I found this formula...

2a (X - Xo) = V^2 - Vo^2

where X and X are location and Origin location (distance basically) and V and Vo are velocities.

So does this formula pass the smell test?

Assuming zeros for starting speed and position Xo and Vo and plugging in 9.8m/s2 for acceleration and V of 30million m/s for 1% light speed.

That works out to 45.45 million meters or 45,000 km?  which is less than a third of an AU.

Is this crazy math?


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Abub's picture
Abub
November 18, 2014 - 1:51pm
Soooo....lets say safest speed in that you wanna be able to react at your 30 hex range in ten minutes incase a planetoid or something is in your way.

That would make your speed 30hex per 10 minutes... or 500km/sec.  That speed would take you 83 hours to cross just one AU.... which would take you like months to make your way from the helisphere to a planet in the habitable zone.

So... basically in order to be game-able you need to be travelling much faster.  The chances of you actually hitting that planetoid in a 10,000 km hex are pretty remote already but it is like playing russian roulette


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Abub's picture
Abub
November 18, 2014 - 2:27pm
ok, if we try 30 hex in a 6 second turn where a PC can act and we get 50000 km / s

so your down to 0.83 hours per AU you cross.  That could still be 3 galactic days to travel say 100AU into system.

Maybe that is gameable....  

Part of my madness is to be able to set the expectation of space travel.  In the cases where travel time is just off-screen time passing the extra detail doesn't matter, but I am thinking I need to establish that the ship is sailing in system for a while so adventure opertunities can unfold there... distress calls, other ships being picked up on the energy sensors (obviously non-ionic) lurking around.

So lets say 50000 km/s is a safe cruising speed in system.  Perhaps a little higher than that and a little lower than that as ships might want to flip multiple times at the cruising speed to provide the linear acceleration gravity.  So say at 1 g, maybe go up to 50705 km/s and down to 49,295 km/s as 705 km/s is about 20 hours acceleration at 1 g.

Hmm... problem with this... 50000km/s takes you 70 galactic days to stop at 1g.



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Stormcrow's picture
Stormcrow
November 18, 2014 - 3:01pm
General formula:
velocity = acceleration × time

Let:
j = jump velocity = 0.01c = 3×106 m/s
g = 1 standard gravity = 9.8 m/s2
t = time to accelerate to jump velocity from orbit (neglecting orbital velocity)

j = gt
t = j/g
t = (3×106 m/s) / (9.8 m/s2)
t = 3.06×105 s = 85 h

General formula:
distance = acceleration × time2

Let:
d = distance from planet at jump point
g = 1 standard gravity = 9.8 m/s2
t = 85 h = 3.06×105 s

d = gt2
d = (9.8 m/s2) (3.06×105 s)2
d = 9.183×1011 m = 6.138 AU

So traveling at 1 g for 85 hours will get you from Earth to somewhere between the orbits of Jupiter and Saturn when you enter the Void if you go directly away from the sun.

Abub's picture
Abub
November 18, 2014 - 3:20pm
bah... my distance formula is either wrong or I used it wrong.

Sooo... 3,000,000 m/s is close enough for government work to 1% light speed.

at 9.8 m/s^2 that takes 85 hours to slow down to roughly zero by simple division.

using a formula of y = 1/2 a (t^2) where y is distance, a acceleration and t is time I get 4.588164e+11 meters, which is 3.058776 AU.

travelling at 3,000,000 m/s is slower than my 50,000km/s value.

It would take you 13.89 hours to cross one AU.  That is sounding like you must be dropping out of the void inside the heliosphere otherwise it would be taking you months to travel to the habitable zone of a system.  It also means you need to know where the actual destination planet is in its orbit and not simply the star itself.

coming out of the void on the wrong side of the star but near the orbital path of the target planet could mean months of time flying around the star... perhaps even a whole second void jump.

Subspace Boeys... it is the only way to get that detailed info to the ship attempting a void jump.


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Stormcrow's picture
Stormcrow
November 18, 2014 - 7:10pm
Abub wrote:
It also means you need to know where the actual destination planet is in its orbit and not simply the star itself.

Yes, this is part of those many-hour computations an astrogator goes through before the ship jumps. The calculations will make you drop out of the Void at just the right place to begin decelerating to reach your final destination.

Even if you missed your target for some reason, a starship will only require some number of days to fly around a solar system, not months.

TerlObar's picture
TerlObar
November 18, 2014 - 8:16pm
Looks like you guys got it all sorted out before I got here. Smile  At 1g = 9.8m/s/s (i typically use 10 for simplicity) it takes about 85 hours to get to 1% c and you cover just over 3 AU in that time.  (Stromcrow was missing a 1/2 in his distance formula.)

You do have to know exactly where the planets are as you come out of the void fairly close but that information should be just part of the astrogations software as the positions of the planets are known for all the inhabited systems.  If you know the date you know were every major body is in all the systems as their orbits are well known.

I typically treat Void jumping as slightly imprecise so you don't always come out exactly where you want but could be off by many millions of kilometers.  Plus the destination planet may be on the other side of the star from the direction you are traveling and you may need to stay at higher speeds to traverse the system.  This could be done by coasting but then you're in freefall the entire time.  I typically like to think of it happening by short periods of decleration and then reaccleration keeping the simulated gravity on the ship until you are in the right place to start your final deceleration. To keep it simple you could just say that a jump takes 8.5+1d5-1 days to account for those variations.

As for turning, you're not going to do it quickly.  You could change your vector slightly to avoid hitting something given enough warning.  If you want math on that I could work something up.  If you want to get a little bit of a feel for it, go read the Vector Movement rules in Star Frontiersman issue 11.  That is a realistic space movement system on the board map and you can get a feel for how ships really move in space and what it takes to turn around or change direction.
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Abub's picture
Abub
November 18, 2014 - 9:20pm
i believe i've read that one... where you track velocity per hex side.

I'm not going to bust out my vector "rule of thumb" here.  lol


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Shadow Shack's picture
Shadow Shack
November 19, 2014 - 1:33am
85 hours to reach 1%C at 1G.

Like I said, you still can't calculate a jump fast enough to beat the ship's performance. The shortest jump is the four LY hop from Cassidine to Dramune. The astrogator needs a total of 40 hours to plot that one, and still needs sleep along the way. Assuming ten hours of work split by ten hours of sleep, that 1G acceleration gives just enough time to plot that jump. Or four 20hr GST days, but you still need to slow down on the other end of the jump.

Which kind of blows the whole 1 day per LY rule.

That 14LY haul from Prenglar to Gruna Garu requires 140hrs of plotting, of fourteen days for the astrogator asuming ten on/ten off work hours. Plus the four days of deceleration on the other end. It would seem more appropriate to rule 1 day/light year plus four days for any jump, unless your astrogator has the foresight to start crunching numbers long before take off.
I'm not overly fond of Zeb's Guide...nor do I have any qualms stating why. Tongue out

My SF website

Stormcrow's picture
Stormcrow
November 19, 2014 - 8:38am
You're right about the 1/2. My bad!

We always get hung up about the contradiction between astrogation time and how long it takes to get to 1% of c. But where do we get the 1-light-year-per-day or 1-day-per-light-year rule?

Alpha Dawn tells us this regarding starliners on which the player characters are mere characters.

Knight Hawks tells us this on the Frontier Deployment Map. But this is for use in the Second Sathar War.

Suppose 1-day-per-light-year is only a simplification for play, like allowing spaceships to fly in circles in the board game? The real time to travel would be in the astrogation skill rules. Military vessels in the Second Sathar War, and starliners run by corporations, employ multiple astrogators to keep the calculations going while some of them sleep.

If this is the case, then the time to go from start point to destination is the time it takes to calculate the jump or the time it takes to reach 1% of c, whichever is greater, plus the time it takes to decelerate to zero from 1% of c.

To avoid allowing astrogators to plot a course prior to ever leaving the start planet, assume that part of the astrogation calculations is constant course corrections while accelerating, plus taking readings and measurements ("Engine 3 is putting out 0.00004% additional thrust; please compensate with a counterclockwise yaw of 0.00057 degrees").

It's possible that charted routes intentionally tack toward their destinations, to allow 1g of thrust during the entire flight. The voyage from Prenglar to Cassidine is 7 light years. It is known that an astrogator must spend 70 hours of active calculation to jump safely on this route. An astrogator will have to sleep during much of this. Any ship accelerating at 1g will reach 1% of c long before the calculations are done. Therefore the ship begins the trip aimed at an angle to the destination. During the voyage, the astrogator will call for course changes that veer back and forth across the true vector, increasing the overall speed less than it would at 1g. The astrogator can spend any amount of time in leisure activity during this period; any extended time away from calculations will just require a greater correction later. As the calculations are being finished, the astrogator will bring the ship in line with the destination and finally the jump will occur. Thus, 1g acceleration for the entire trip.

So, assuming 1g for the entire trip using the above tacking movement and assuming a single astrogator spending 10 out of 20 hours performing calculations, travel along a charted route from one system to another safely takes a total of one day per light year, plus four days (as Shadow Shack said, above). Vessels with more astrogators can cut down this time (like Spacefleet ships), although never to less than [half the distance in light years] in days, plus four days. Unfortunately, this still does not match the 1-day-per-light-year rule.

Stormcrow's picture
Stormcrow
November 19, 2014 - 9:02am
Here's an interesting take on the problem: slingshot effect

I'm not sure it solves it any better, but requiring a slingshot breakaway to control a Void jump would be interesting.

Abub's picture
Abub
November 19, 2014 - 10:21am
Storm... turning a ship going that fast (1%) is nearly impossible without days of thrust.
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Stormcrow's picture
Stormcrow
November 19, 2014 - 11:12am
Not turning, veering. Tacking. Your forward vector continues, but you add a slight perpendicular vector that you switch up regularly.

Abub's picture
Abub
November 20, 2014 - 1:16pm
So i'm wondering how fast you could slow down... and braking at 6g would still take you like 14 hours to stop.  So... i guess responding to that distress call... had better be luck that they are calling from where you are stopping at anyways cause by the time you slow down and turn around they are doomed.

How many hours do you think a crew could take 6g?  I don't think there is a lot in the way of actual research for long duration high G effects.  wikipedia (cause if it ain't on wiki it isn't known right?)... seems to indicate high G tests but only for short durations of like 10 minutes.  I'm wondering about hours.

And maybe if you think higher than 6g could be endured for longer?  In Battletech books they sometimes do 2g burns to rush to a planet... but they mention that it fatigues the people from enduring it for the hours they do it.
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TerlObar's picture
TerlObar
November 20, 2014 - 3:21pm
I vaguely remember reading somewhere that 6g can only be withstood for a short time (< 1hr) before serious complications occur.  Some of the early astronauts endured up to 8g's as part of the launch getting into orbit but it only takes a few minutes (~8) to get into orbit.  While Gizmodo isn't always the best source, this article (http://gizmodo.com/why-the-human-body-cant-handle-heavy-acceleration-1640491171) is of interest and has some links to other sources as well.
Ad Astra Per Ardua!
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jedion357's picture
jedion357
November 20, 2014 - 5:06pm
Inertia field technology allows SF military ships to maintain high G accel/decel without harm to the crew and passengers.
I might not be a dralasite, vrusk or yazirian but I do play one in Star Frontiers!

Abub's picture
Abub
November 20, 2014 - 9:06pm
yeah there is the magic... pandora's box inertia fields.  The tech that is just close enough to gravity tech to logically change everything in the system.


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Abub's picture
Abub
November 20, 2014 - 9:16pm
I wonder.... could there be anything medically administered to the crew to enpower them to sustain higher G force for longer durations.  

Nanobots is all I got... that are able to halt rapid blood movement... maybe something that makes your blood thicker without killing you from doing it so it is less prone to tearing blood vessels/capilaries.


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Abub's picture
Abub
November 20, 2014 - 9:19pm
or maybe something given to the crew after a prolonged high g de/acceration to reverse the damage caused by the g force.

I mean i assume the long life spans are mostly from medical technology prolonging life through treatment, so humans on a low tech planet or extreemly poor planet might not live longer then thier 50s... the two hundred years might be an average... if you are rich and can afford it, you might live to be 300.

I know we discussed this in the past... the lifespan thing.
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Tollon's picture
Tollon
November 20, 2014 - 11:22pm

On the subject of calculating void jumps: I stated the above paragraph in another thread.

 

“A ship carrying passengers and cargo from Point A to Point B doesn’t need to calculate Point B if it is a standard route.  These standardized routes are built into a nav computer or avionics’ package of the ship.   As long as the ship remains in good condition, there shouldn’t be a problem with navigating these routes.  Only smugglers, pirates, military and research ships need an astronav, since they are the ones looking for different ways to evade, find or locate planets and authorities by going off the beaten path.”

 

 

What the game designer should have said, “There is no penalty for ships traveling charted routes if the astonavigator spends at least 40 hours reviewing the ship’s course against known jump routes.  It is only when players are exploring uncharted areas of space that is when the astronavigator must spend 10 hours per light year plotting and calculating the jump to the next star system. (Refer to the skill Chart new Route.) ”

 

A simpler way of doing this would have been to avoiding this all together by simply stating:

 

“One day to leave the planet and reach safe jump point.  Travel time to the next planet (see Star Frontiers map for travel times).  His ship will exit void space 1 day away from the planet.”  or  “Add two days to the travel times per the Star Frontier Map.  This allows for the ship to take off and reach a safe jump distance.   Exit at a safe jump distance and land on the planet he has selected.  So a trip of 8 light years would take 10 days due to safety concerns and take off and landing.”

 

Either solution would have solved the problem.


jedion357's picture
jedion357
November 21, 2014 - 3:47am
Medically? the effects in play are inertia pulling blood and fluids to the lower extremities. Too much of that and the brain blacks out. Real world counter is a flight suit that compresses the extremities to force the fluid to stay up. Hard to immagine nan bots or drug even being an effective counter.

Either state that military ships mostly accel/decel at 1g and that beating to general quarters involves the crew strapping into acceleration couches for the limited time at high G maneuvers. This however ignores that an engineer is doing repairs during combat.

or use the pandora box that is already part of the setting since it would have a logical application in this area.
Not unusual that a technology developed for military purposes would have multiple applications: radar- the radar range (microwave oven)

Unless there is some RW tech the US government has for its fighter pilots that it hasn't told everyone else about yet?

EDIT: High G manuevers have another problem besides the biological effects on crew. Items not strapped down will become projectiles within the ship during high G maneuvers. a ships fitting that is bolted down and therefore considered safe will have its bolts fatigue over time and they will break and this fitting becomes a very heavy projectile smashing everything it strikes. That inertia or Negative G field is starting sound like a good idea to me before I board a Frontier ship with an atomic drive.

In the end the setting has ships doing sustained high G manuevers that would have several serious effects and while it does not explain how it is that these serious effects are not a problem is implied that they are not. So I suggest going with the simplest answer on this and that pretty much going to boil down to "they have technology that solves this problem"
I might not be a dralasite, vrusk or yazirian but I do play one in Star Frontiers!

iggy's picture
iggy
November 21, 2014 - 10:17pm
I have pondered a bit about implanted pumps that kick in under high G to assist blood flow and other fluid functions.  Any medical experts out there that can speak on this?  As an engineer this is what I would do to systems in the ship to help them withstand high G.
-iggy

KRingway's picture
KRingway
November 22, 2014 - 8:58am
Perhaps it's more of a problem for human-like races (humans, Yazirians, Humma, Ifshnits etc)? One wonders if dralasites and vrusk are more capable of dealing with higher Gs.

iggy's picture
iggy
November 22, 2014 - 8:21pm
I see dralasites as being able to handle higher Gs better because their systems have a more adaptable circulatory system to support their shape changing ability.
-iggy

Shadow Shack's picture
Shadow Shack
November 23, 2014 - 5:04pm
iggy wrote:
I see dralasites as being able to handle higher Gs better because their systems have a more adaptable circulatory system to support their shape changing ability.

Either that or said physiology makes it easier for them to become pancakes.
I'm not overly fond of Zeb's Guide...nor do I have any qualms stating why. Tongue out

My SF website

jedion357's picture
jedion357
November 23, 2014 - 6:53pm
Shadow Shack wrote:
iggy wrote:
I see dralasites as being able to handle higher Gs better because their systems have a more adaptable circulatory system to support their shape changing ability.

Either that or said physiology makes it easier for them to become pancakes.


I'd second that.
I might not be a dralasite, vrusk or yazirian but I do play one in Star Frontiers!

Abub's picture
Abub
November 24, 2014 - 6:44am
I'll take three Drals with butter and syrup please.  and a side of bacon.
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Shadow Shack's picture
Shadow Shack
November 24, 2014 - 10:38pm
Abub wrote:
I'll take three Drals with butter and syrup please.

A.K.A. the "short stack". 

Aptly named after the shortest race in the Frontier.
I'm not overly fond of Zeb's Guide...nor do I have any qualms stating why. Tongue out

My SF website