Star Frontiers® Conundrum #1: Interstellar Travel Times

Contrarian,

Sorting Out the Star Frontiers® Space Travel
Rules

My problem is this: A close reading of the scattered space travel rules in the Star Frontiers Knight Hawks rules reveal some irritating contradictions concerning interstellar travel times. The most logical resolution of those contradictions is to make one small but significant change to the Knight Hawks astrogation rules.

Believe me, I am not the kind of guy who changes rules a lot (My philosophy is "I paid good money for the Star Frontiers rulebooks; damn straight I’m going to use those rules."), so if I say the rule needs to be changed, then it really, truly, needs to be changed. At least hear me out on this one, okay?

Anyway, interstellar travel in Star Frontiers has two important facets: the actual travel (acceleration, jump, and deceleration), and astrogation (plotting the course). We’ll need to take a close look (with lots of quotations from the rulebooks) at each part to see what the problem is.

A quick overview of FTL travel

The original Star Frontiers rules don’t say much about space travel. In fact, all the Alpha Dawn Expanded Rules (page 49) state is:

The length of each route in light-years is printed on each route. Because FTL ships travel one light-year per day, this number also is the number of days required to travel this route. This time includes take-off and landing, maneuvering in orbit, passenger loading and all other normal procedures.

That’s it. All of us poor SF players and referees had to wait until the Knight Hawks rules were released for details of faster-than-light travel. Fortunately, the Knight Hawks Campaign Book Expansion Rules didn’t waste much time, and explained how FTL drives work on page 3 (under the topic "Interstellar Travel"):

The discovery that allowed the members of the four races to expand beyond their home worlds and enter the Frontier was purely accidental. It occurred when spaceships were developed that could accelerate to a speed of about 12 million km per hour (1% of the speed of light). At this speed, a unique reality of space becomes apparent, in defiance of all previously accepted laws of physics, a ship will disappear from the space known as the universe and enter a region called "the Void".

Knowing the basics of Star Frontiers FTL drive (ironic as that phrase is, since no special drive is required) suggests a few questions about the details of the FTL experience. By asking these questions (and digging the answers out of the Knight Hawks rules), we’ll be figure out exactly where all that time is going, and find an interesting flaw in the rules.

Those "few questions" are:


How long does a ship spend in the Void?

Starships spend so little time in the Void that it’s negligible for purposes of this discussion. Returning to page 3 of Knight Hawks reveals:

Time is very distorted in the Void and space does not seem to exist at all. If a ship decelerates slightly while in the Void, it will emerge into the "real" universe at some point far distant from where it left the universe. By carefully coordinating the ship’s direction with the length of time the ship spends in Void (usually 3 to 15 seconds), a navigator can "jump" his ship into the vicinity of another star.

How long does it take to reach jump speed?

If jumping light-years through the Void only takes seconds, then why does interstellar travel take 1 day per light year? (Landing and take-off maneuvers add some time, but they couldn’t possibly add that much time.) Returning one last time to page 3 of Knight Hawks, we find:

Although this process of jumping through the Void allows ships to cover immense distances in very short times, jumping still takes several days. Most of this time is spent accelerating to jump speed and decelerating at the other end.

Remember, a ship jumps into the Void when it reaches "12 million km per hour (approximately 1% of the speed of light)". Here’s a little problem — The Campaign Book got the speed of light wrong! In Star Frontiers, the speed of light is exactly 300,000 kilometers/second. 300,000 x 60 x 60 equals 1,080,000,000 kmph . The "1% of the speed of light" needed for jumping to the Void is therefore 10,800,000 kmph. Given the contradiction, we’re free to choose which speed we’re basing our calculation on. We’re going to use the 10.8 million kmph because it makes the math cleaner. (The "Dispel Confusion" column of Polyhedron® Newszine also prefers the 10.8 million kmph figure — see the Afterword.)

Page 33 of the Campaign Book tells us the rate of acceleration for a ship approaching a jump:

On a normal interstellar voyage, the starship pulls away from the space station and begins accelerating at 1 g toward its destination star. This is about the same acceleration a ship uses when it increases its speed on the boardgame map by one hex per turn.

For those of you who don’t remember the Basic and Advanced Boardgame Rules, here’s an important paragraph from page 2:

One turn in this game equals 10 minutes of time. Each hex is 10,000 km across.

We’ve already established that jumps occur at 10,800,000 kmph. Dividing that speed by 10,000 reveals that jump speed is 1,080 hexes per hour. Dividing 1,080 by 6 (the number of turns in one hour) simplifies jump speed to 180 hexes per turn.

How long does it take to reach 180 hexes per turn, accelerating at one hex per turn? Just 180 turns, or 30 hours — That’s 1.5 GST days. Assuming that deceleration takes the same amount of time, every interstellar voyage on the Frontier takes three days, plus take-off and landing time.

(By the way, if we had decided to use 12 million kmph as our jumping speed instead of 10.8 million, it would still only take 200 turns (33.34 hours) to reach jump speed.)

When does the ship jump?

A careful reading of the rules for The Second Sathar War (pages 55-60 of the Campaign Book) reveals that a starship makes its jump approximately half-way through an interstellar trip. Describing the Frontier Deployment Map (page 56) "Transit Boxes", the rules say:

The paths of light blue boxes between systems mark the known travel routes of the Frontier. The boxes are "transit boxes." Each box marks one day of acceleration or deceleration along that route.

In other words, travel on the Frontier Deployment Map is one day per transit box. The length of each route (in transit boxes) on the Deployment Map, conveniently enough, is equal to the length of the same route (in light-years) on the AD Frontier Map — the Frontier Deployment Map is just a more abstract representation of the same old Frontier. Under "Using The Transit Boxes" (page 57) the wargame rules state:

When the ship(s) enter a dark blue box marked with an arrow pointing in the same direction the ships are travelling, the ships have jumped into the next system and are decelerating towards that star.

Look at the Frontier Deployment Map. The dark blue boxes with arrows are all at the half-way points of their respective routes. Ergo, the jump through the Void occurs half-way through a voyage. This may not seem important right now, but it’s a critical fact later on in this discussion.

How long does it take to plot a jump?


So far, we’ve determined that neither the time spent in the Void, nor the time accelerating/decelerating to jump speed is long enough to slow interstellar travel to 1 ly/day. Based strictly on acceleration rates and Void speeds, every interstellar trip on the Frontier should last barely 3 days. There must be some other factor limiting effective travel speeds. At this point, there’s only one factor left to consider: plotting the interstellar jump.

The description of the Astrogation skill on page 25 of the Campaign Book explains how long it takes to plot a normal interstellar jump:

Normal plotting time for a jump is 10 hours for each light-year that will be jumped. For example, an astrogator plotting a 8 light-year jump must spend 80 hours performing calculations before the ship could accelerate to jump speed. The time must be spent actually making calculations; the referee should remember that astrogators need to sleep sometime.

The comment about sleeping calls to mind page 52 of the Expanded Rules:

A standard year is divided into 400 20-hour days. Each day is divided into a 10-hour work period and a 10-hour rest period.

So, taking that the Frontier’s standard workday into account, it takes one full work day (per light year) to plot an interstellar route. The time to plot a course is now equal to the length of the trip!

It seems as if the 1 ly/day speed limit of the Frontier is a result of astrogation calculations taking so long. The "Risk Jumping" rules for the Second Sathar War game (page 50) seemingly agree, because they let starships accelerate movement (on the Frontier Deployment Map) by risk jumping (reducing the amount of time spent calculating the route). That only makes sense if the astrogation time is the limiting factor on fleet speed:

As some point in the war, both sides are likely to find themselves in an urgent situation where the need to move their ships more than one transit box per day. This can be done by risk-jumping.

Players using accelerated jump movement must accept the risk of those ships making a mistake in their jump calculations and becoming lost. The chance that a ship will become lost depends on the ship’s acceleration and the skill of its astrogator. The percentages are summarized on the Mis-jump Probability Table.

Ships with ADF of 2 or more can move two transit boxes per day. Ships with an ADF of 3 or more can move three transit boxes per day. No ship can move more than three transit boxes per day, because such extreme, prolonged acceleration would disable the crew.

Decoding that last paragraph: Ships that cut their astrogation time in half and double acceleration can double their effective FTL speed. Ships that cut their astrogation time by two-thirds and triple their acceleration can triple their effective FTL speed. Taking the increased acceleration into account, the percentages on the Misjump Probability Table still assume the astrogator is working 10 hours per day.

I believe the option of Accelerated Movement should be available to player characters’ starships. If Spacefleet can do it, so the PCs. Apparently, Douglas Niles believes so, too: While calculating the GST months used in SFKH1, I discovered that the last two jumps listed in the Gullwind’s log are only 1/2 and 1/3 the normal travel times.

What exactly was the problem again?

At first, it seems like we’ve solved the problem: ships travel 1 ly/day because that’s how long it takes the astrogator to plot a course. One complication, though: the Astrogation skill description indirectly insists the astrogators finishes "performing calculations before the ship could accelerate to jump speed" and the Second Sathar War insists that jumps occur half-way through a voyage. Our new problem:

If plotting a course takes the same amount of time as travelling the course, but plotting has to be finished before travelling half the trip, the astrogator has to begin plotting the course before the ship leaves a planet.

While not a problem for PCs using
commercial starliners (Nobody cares when corporate astrogators started plotting a course), it’s horrible for characters who run their own starships, because it effectively increases the time needed to travel a given distance by 50%. An 8 light-year trip for example, needs 8 days of course plotting, which needs to started 4 days before launch, so that the jump can occur 4 days into the trip. Ouch.

From a player’s point of view, astrogation just became the least-exciting job on the Frontier. If your players think they’re in a hurry (and believe me, players almost always think they are), every time they set down on a mysterious planet, they’ll lock their astrogator in the ship and tell him to start plotting the next jump out. I don’t foresee any PC astrogators volunteering for this kind of duty.

There’s no room for spontaneity in space travel, either: Players can’t jump in their ship and fly to the next star system without several days warning, and/or risk jumping. If they cut their plotting time in half, they can do all the plotting during acceleration to jump speed, but the chance of success ranges from only 60% to 95%, depending on the astrogator’s skill level.)

(You might be thinking: Maybe navigation within a star system is so complex that the astrogator is plotting the course until the ship reaches its destination planet. Sounds like a promising way to stay official, but it doesn’t quite work: all the Astrogation skill checks are written as if calculation time is calculated before the skill check. Calculating after the skill check is slightly nonsensical in normal play (It means success is determined half way through the skill use — what happens if something interrupts the astrogator after a successful jump?) and very nonsensical during risk jumps (Misjumps are usually shorter, in terms of light-years, than successful ones — why would the astrogator keep calculating after he knows he blew a jump?). Calculations after a jump would also imply that a ship needs an astrogator for system travel, but the Astrogation skill description mentions nothing about system travel. I don’t think this is the answer.)

What’s the solution?

You’ve probably lost patience with this whole discussion by now, and keep wondering what my point is. My working hypothesis is this: TSR’s designers realized that starship acceleration/deceleration doesn’t take 1 day per light-year, so they made the Astrogation skill time-consuming enough to slow down travel to the established Alpha Dawn speed. Somehow, the designers forgot that the jump has to occur at the half-way point, and made astrogation require twice the time it should: A strict interpretation of the astrogation rules will make all PC-plotted interstellar journeys 50% slower than commercial starliners.

The easiest way to fix the interstellar travel rules is to reduce course-plotting time to 5 hours per light year to be travelled. Doing so eliminates the vicious contradiction between the Astrogation rules and the wargame rules, creating a system that’s closer to what (I believe) the Star Frontiers design team intended.

With one change, plotting an interstellar jump now requires a half-day per light-year, so all the plotting is be done before entering the Void, but normal travel still requires one day per light-year. (In other words, the total time to travel an interstellar route is twice the time required to plot the route, or 3 days, whichever is greater.) Characters can shorten their travel time (as in the wargame rules) by increasing their ship’s acceleration and shortening plotting time (using the Risk Jumping subskill).

Making this change frees the astrogator from his console (plotting a jump is a full-time job during the first half of an interstellar trip, but the character is free to do other things during deceleration, and doesn’t need to be locked in the ship when planetside), and gives ambitious characters a way to travel through the Frontier faster. It’s a more elegant system than the contradictory Knight Hawks rules, and more flexible. That’s a win-win situation.

The text between the next two horizontal rules takes everything derived from this analysis and distills it down to some relatively simple rules.


Expanded Rules for Interstellar Travel

Plotting Interstellar Jumps


Normal plotting time for a jump is 5 hours for each light-year that will be jumped. Plotting a course is a full-time ship duty, and astrogators are still limited to 10 hours of plotting per day, as per Knight Hawks page 25, and Alpha Dawn, page 52.

(To adjust the success rate for the Risk Jumping subskill to accommodate this change, multiply the number of hours spent plotting the course by 2 before entering the number into the normal formula.)

Accelerating to Jump Speed


An astrogator’s plotting calculations are performed between leaving a planet and entering the Void. Under normal conditions, ships do not accelerate more than 1 hex/turn, but they often accelerate less. A normal acceleration phase lasts twice as long as it takes to plot a course, or 30 hours, whichever is greater.

(Crews desiring constant acceleration for trips longer than 3 light-years accelerate the ship at an ADF equal to (358/120L)^2, where variable L is the distance in light-years to be travelled.)

Jumping


Jumpspeed is .01c (180 hexes/turn). A jump through the Void lasts one second per light-year jumped.

Decelerating from Jump Speed


Under normal conditions, ships decelerate from jump speed at the same rate they accelerated to it, making the post-jump portion of the trip the same length as the pre-jump portion.

Total Travel Time


Total minimum trip time therefore equals plotting time times 4 (i.e. 2 days of travel for every day of plotting), or 60 hours (3 days), whichever is greater.

Ion Drives


Ships with ion engines use 180 units of fuel (per engine) to accelerate from zero speed to jump speed, and an identical amount to decelerate back to zero.

Accelerated Movement


Ships with atomic engines can decrease travel time by increasing acceleration and reducing plotting time (using the Astrogation subskill Risk Jumping).

Ships with ADF 2
can reduce minimum trip time to equal course-plotting time or 30 hours, whichever is greater. Ships with ADF 3 can reduce minimum trip time to plotting time or 20 hours, whichever is greater. As stated on page 58 of Knight Hawks, no ship can accelerate jump movement beyond a factor of 3.

Ships with unrepaired hull damage cannot accelerate movement.

(Referees should assume that corporate starships never accelerate movement — It’s very expensive replacing lost starships, and not many passengers appreciate 2G acceleration. Military ships accelerate movement only in emergencies. This guideline allows small companies and tramp freighters (the kind player characters often run) to carve out a market niche by accepting "high speed, high cost, high risk" missions.)


Optional Rules for Interstellar Travel

Now that I’ve gotten space travel back to what I think it was meant to be, I should just stop and go home. Instead, I’m going to provide four very optional rules that add some flexibility to the system. Of course, all experienced role-playing referees know that "flexibility" is a codeword for "complexity", so don’t use them if you don’t want any more work. (At this point, I wouldn’t blame you.)

Hard Braking


If players don’t want to chance jumping all over the Frontier by Risk Jumping, but still want to shave some travel time off voyages, they can split the difference by only increasing post-jump deceleration. (Even if you don’t tell them about this, they’ll figure it out soon enough.) Spacers call this "hard braking". Hard braking at ADF 2 reduces total travel time by 25%, while hard braking at ADF 3 reduces total travel time by 33%.

(According to SFAC3: The War Machine, Sathar can handle prolonged acclerations up to ADF 6. Hard braking at ADFs 4, 5, and 6 reduce total travel time by 38%, 40%, and 42%, respectively.)

Multiple Astrogators


Astrogators cannot reduce course plotting time by working together, but they can work on the same course in alternating 10-hours shifts. Two astrogators working in rotation can therefore plot 4 light-years per 20-hour day, allowing a ship to accelerate movement by ADF 2 without needing to make a Risk Jumping skill check.

If two rotating astrogators are plotting a ADF 3 accelerated jump, they’re still Risk Jumping, however. The Referee should use the astrogators’ average skill level for determining success of jump.

Express Routes


With rotating astrogators to plot jump courses, commercial starliners can safely cut their travel time in half without risk of mis-jumping. At the Referee’s option, some commercial companies in the campaign offer express routes that travel known routes in half the standard time.

As noted earlier, not everyone wants to travel around the Frontier at 2G, so express routes should be rarer (and more expensive) than regular space routes. Express routes only exist on direct routes between Population M and/or H worlds, and tickets cost three times the base price for those routes.

Ship Stress


On the other hand, if the Referee thinks PCs are using the accelerated movement rules too much, s/he can rule that accelerating movement can increase the chance a ship will break down (see Knight Hawks page 10 for base breakdown probabilities). Ships accelerating/decelerating at ADF 2 increase the chance of breakdown (for that voyage only) by 1% per day of accelerated movement. Ships accelerating/decelerating at ADF 3 increase the chance of breakdown by 2% per day of accelerated jump movement.

The Referee could also rule that ships which are regularly over-accelerated need engine overhauls and/or annual maintenance more often than normal, but I can’t come up with a tidy system for that. You’re on your own there.


Afterword

Some time after putting up this page (and a long time after I devised this system for my own use), I bought an old copy of Polyhedron Newszine #19, which contains two FTL-related questions in the "Dispel Confusion" column. The first question pursues a line of logic similar to this page, leading the "DQ" writer (probably Penny Petticord) to state that astrogation calculations must be started after a ship leaves a planet. The second question asks how many units of fuel an ion drive needs to reach jump speed — the answer given (180 units) agrees with my decision to make jumpspeed 180 hexes/turn. As far as I know, Polyhedron #19 is the only TSR literature outside of the Knight Hawks rules that discuss FTL travel. (The funny thing is, I bought the issue because it had a Gamma World® article I wanted to read.)

That’s it, finally. We’re all done (except for the disclaimer, anyway). Think this page was too long? You should have seen the first two drafts….

Star Frontiers

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