[2300AD] Pushing the Stutterwarp Drive


While I was looking at the side branches of the French Arm (I’m still working on it!), I found a group of systems that were 7.769ly from the nearest star on one of the side branches. Which got me to wonder – what happens if a system in the 2300AD setting is slightly over 7.7 ly away – between 7.7 to 7.8ly? Can people still reach it without tugs or multiple drives/tuning? Do they have to “push the drive” even for such a small increment?

Let’s have a look at how “pushing the drive” really works (using the MGT rules). The rules say: “Pushing a stutterwarp drive past its discharge limit: 1–6 hours, Very Difficult, range increased by Effect x10%.” So when do you start “pushing the drive”? I’d guess no later than 6 hours before it gets to 7.7 ly (otherwise you wouldn’t be able to finish before hitting the limit).

Getting into the nitty-gritty of the game engine, I guess theoretically an engineer could spend a lot of time on it (reduce by two timesteps to 10-60 hours – so break out the coffee and stims!) to knock the DM penalty from DM-4 to DM-2. I’d imagine most engineers would have skill level 2-3 (DM +2 or +3), and Int or Edu of at least 9-11 (DM+1) – let’s just say that a competent engineer should be able to get a DM+4 between their skill and characteristic. So if they spend 10-60 hrs on it they’d be rolling 2d6 against difficulty 8 with a net DM of +2, which would give them a 72% chance of success. Though granted, it’s unlikely they’d be able to do the task for 10-60 hours (on their own at least) – at worst I think they’d just do it at Very Difficult with 1-6 hours and have all the DMs cancel out for a 42% chance of success. It seems to me that a competent engineer could reasonably be willing to spend at least 6-24 hours to push the drive to get a 58% chance of success with no possibility of destroying the ship (though there’s still a 42% chance that he’ll destroy the drive, so it’s probably not something that would be tried regularly).

Exceptional Failure only occurs if the Effect is -6 or less (I think that’s what the rules mean – not less than -6, since -6 isn’t on the table otherwise), so they’d only have a 2.8% chance of exploding the ship if they didn’t take more time to do it (Very difficult, no DMs, 8+ required) – otherwise Exceptional Failures can’t happen if there are net positive DMs. Though Average or Marginal Failures still at least disable the drive (I’d imagine the drive would just explode but not necessarily destroy the ship with it, and the the ship would suddenly drop out of stutterwarp).

If the roll succeeds, then there’s a decent chance that the range is increased by 10-30% (the chance is lower for the 40-60% increase, since that would require bigger effect – though spending longer on the roll would make those more likely) – so theoretically a drive has a reasonable chance of being pushed to 10.01 lightyears (maybe up to 12.32 ly if the engineer is very good and very lucky)!

So the question really is whether all this is even necessary to go slightly over 7.700 ly. If it is, then I guess it’s not going to be very likely that anyone would want to be regularly heading out to systems that are even 7.71 – 7.80 lightyears away since there’s a significant chance the drive would be destroyed/rendered inoperative (even though it’s at most about 1-2% further in range). Maybe risk-taking explorers would do it, but it wouldn’t be a regular route. Or maybe a 1-2% range increase is OK, but the drive MUST be checked over/recalibrated/retuned at the destination (after discharging) before it can be reused? I’d be more inclined to go with the latter option – it adds possibilities and doesn’t seem unreasonable.

Extending the drive range

There are at least three options (possibly more) to increase the range of the drive:

First is the aforementioned “pushing the drive”, which seems to have been introduced in MGT. Ordinarily the gravistatic charge is allowed to collect wherever it falls and some part of the drive will reach saturation around 7.7 ly (necessitating a discharge at that point, or there will be explosive consequences!), but it is possible to redistribute the charge before it settles (using magnetic field, superconductors, or something other armwave) – this requires intensive computer control and monitoring.

The second option is “delaying discharge”. This option is present in MGT and was also available in the original 2300AD, though it seems to me that it’s not so much “delaying discharge” as “oversaturating the drive” – delaying the discharge would be more like arriving in a system and just letting the charge sit there in the drive without going anywhere for a while (which itself may damage the drive if left too long). Oversaturating the drive on the other hand is letting the charge build up (while the drive is active) to a point beyond that which it should be able to handle – which obviously would be a much riskier endeavour. If “pushing the drive” is distributing the gravistatic charge in a controlled, uniform way so that the largest possible amount of charge can be stored, then “oversaturating the drive” is trying to cram in more charge than it’s actually designed to hold.

The third option is “overclocking the drive”, which would be to make the drive work faster than it’s designed. This was also mentioned in the original 2300AD and in MGT, and was described as putting more power into the drive to increase its efficiency, allowing the ship to travel faster (whereas “pushing the drive” and “oversaturating the drive” would allow the ship to travel for longer). On its own, overclocking would still limit the ship to 7.7 ly max, it just lets it get there in a shorter time because it’s covering more ly/day. I’d imagine that this would be the easiest to do in terms of skill rolls, though exceptional failure would still damage the drive.

The remaining options change how the drive works – increasing the size of the microjumps it makes, increasing the number of cycles (and therefore microjumps) that it makes, reducing the rate at which charge builds up in the drive, and using piloting to increase the speed of the drive (described in MGT 2300AD 1e, p204).

All of this leads me to an interesting conclusion. Given that there are at least three methods of making the drive go further and faster… it could be possible to use all of those methods at the same time. And undoubtedly someone in the setting has thought of doing that in the 164 years since Stutterwarp drives first became practical – some of that research is probably what led to the three types of drive (old commercial, new commercial, military) that operate at different speeds. Humanity has a history of pushing the envelope and finding new techniques to make something work even better than its original designers hoped – just look at engines and aeronautics and CPUs today, for example. So someone in that 164 year period has undoubtedly tried to push the drive to its absolute limits.

We know from “pushing the drive” and “oversaturating the drive” that the absolute limit of a drive cannot be 7.7 ly – that’s just what happens when you don’t monitor and control the charge buildup. The absolute limit is actually 12.32 ly (160% of 7.7 ly, which is what you get with an Effect of 6 when successfully “pushing the drive”). It’s actually even higher than that though, because if you can also oversaturate the drive then it can be active for another 24 hours, which adds at least another lightyear or two to that absolute maximum. And you could also potentially overclock the drive so that it runs faster, which means you’d go further in that 24 hours as well. So I think the real maximum is more like 14 or 15 ly – let’s just call it 15.4 ly – double the usual 7.7 ly limit! And all of that (except “overclocking”, which I’ve added as a presumption) just naturally folds out of what we know in the rules about extending the drive to its limits.

Obviously, attempting all of this on a normal stutterwarp drive would be suicidal – but when you look at the things that push the limits of technology today, they’re not “normal”. The engines of a Stealth Bomber are not the same as the engines for a 747 (even though they have the same principles), and a maximally overclocked CPU doesn’t run on a normal motherboard – it needs special hardware for maximum control and watercooling. So obviously such a “maxed out” stutterwarp drive would be bleeding edge, very experimental and specifically designed to be overtaxed. It would need highly advanced monitoring systems to distribute the charge uniformly on a regular basis without catastrophic failure, it would probably need to be doped with special elements to allow it to hold that extra bit of charge to allow oversaturation, and it would need coils and drive hardware that could allow it to be overclocked without failure. Maybe the design of the drive itself would necessitate changes to the design of the ship too – more radiator fins, or a specific shape (I’m rather fond of rings built around ship hulls, perhaps to smooth out gravitational distortions that the drive would be more sensitive too). Perhaps there’d only be a handful of such drives in existence in 2300AD (10 at most?), many of which exist only as testbeds though there may be one or two installed in X-ships. But I think they would certainly exist, and they would work – whether they’d regularly work at the maximum possible 15.4 ly is another matter. Perhaps that’s still in the future, but I’d expect that by 2300AD these experimental drives would at least somewhat extend the range beyond the normal 7.7 ly drive, to something closer to 9 ly.

And something that falls rather elegantly out of this is that the long-range Eber Drive (which actually needs to cover at least an 11.19 ly gap since that’s the distance between Zeta 2 Reticuli and the nearest star accessible from an Arm) didn’t need any fancy elements or radiation resistance – they just figured out how to do all the overtaxing in their drives and keep it stable so they could do 11+ ly jumps whenever they wanted to.

An obvious adventure hook here is that the characters are the crew of an experimental ship has been kitted out with one of these drives and sent out on a test run to put it through its paces. Perhaps it’s stable enough to be sent out into unexplored space to see what’s out there beyond the normal range of exploration (e.g. the Beta Aquilae cluster!). Or maybe something goes wrong (since the drive isexperimental) and the microjump distance increases to hundreds of kilometres instead of hundreds of metres, and when the drive burns out eventually (but it can be repaired) the PCs find themselves thousands of lightyears from home, and have to get back using their experimental drive with a max range of 9 ly.


In conclusion, I think that extending the drive range by 1-2% is fine – it certainly wouldn’t “break the setting” since only three small (5-6 system) clusters are opened up that have a range between 7.7 and 7.8ly from the nearest star on an Arm. No rolls required, but it does require a thorough maintenance check/retuning/reset at the destination to de-stress the drive and make sure it’s OK. Otherwise the drive could malfunction or break down catastrophically next time it’s used.

Pushing the drive, “delaying discharge”, overclocking, and anything else are all extremely risky manoeuvres on a normal stutterwarp drive, as described in the rules. These wouldn’t be attempted normally unless there was some desperate requirement to do so, since the ship could be destroyed. There are experimental drives that are specifically designed to function without exploding or failing under these conditions, but these experimental drives cannot be further pushed, over-saturated, or overclocked because they’re already operating at their maximum design limits.

Obviously, allowing the drive limits to expand this would affect the setting, but I think that’s fine. 2300AD isn’t and shouldn’t be a static setting – technology doesn’t stop advancing, and no group working on stutterwarp technology in the setting is going to care about whether “the arms are broken” as a result of their work. No visionary research group or company has ever said “we’d better not do this because it may disrupt existing technologies or change the way of doing things” – the whole *point* is to disrupt the status quo, because doing so will give the developers a lot of advantages over their competition. And in 2300AD, given the war footing and existential threat of the Kafers, there is absolutely going to be a strong impetus to get an edge on them. So while these drives may still be experimental I would expect that at least the more stable designs that extended the range would become a lot more mainstream in the very near future of the setting – and yes, that would mean that arms would change. Even then though, it would probably only mean that certain worlds can be bypassed – I can’t imagine that the ‘big colonies’ like Beta Comae and Beta Canum would be suddenly overlooked even if they could be skipped. That’s just progress for you (and in itself would open a huge host of adventuring opportunities as the status quo is disrupted).

Ultimately, these extended range drives are not only possible but likely (albeit experimental) – and they can only become more mainstream in the near future.

11 Replies to “[2300AD] Pushing the Stutterwarp Drive”

  1. Thanks for sorting out comment posting!

    Several things come to mind here:

    ① The downside to a failed push/oversaturate is that you have no drive, the ship is irradiated, and you’re hundreds or thousands of AUs from rescue. (I don’t remember the details of the irradiation, but I think it was of the “kills everyone on board” variety.)

    ② Back in the day, when we were using paper starmaps, adding new routes and worlds would have been really hard work. (I imagine it took a fair bit of effort for GDW to come up with the routes they did.) Now it’s much more plausible – you have to do the work to set up the route calculator, but then you can just tweak effective range and instantly see the result..

    ③ You can actually get arbitrarily close to twice the range limit without pushing the drives at all, or throwing them away. Two ships travel to half the limit; one of them is using a podded drive rather than its built-in one. The podded drive (still online) is transferred to the second ship, which heads back to the start point. The first ship fires up its internal drive and heads onwards. That gets you to 150% of the limit, and you can stage this as many times as you like.

  2. I totally agree with this.
    Unmanned experimental probes with test drives would be used to push the boundaries and send back telemetry. The problem is, how to get the telemetry once it arrived…

    1. Well, how long are you willing to wait? If the probe carries a message torpedo which goes as far as it can and then sends a radio signal, that can take 7.7 years off the lightspeed reporting-back time. If you’re extending by less than 50%, you can bring a ship out 3.85LY to where the message torpedo is going to arrive, copy its message, then abandon the torpedo and go home.

  3. “probably what led to the three types of drive (old commercial, new commercial, military)”

    Ive always assumed that was manufacturing efficiency similar to pc chips ie a combination of purer materials, finer tolerances etc etc

    I havent tried the newer mongoose rules but there is another factor to consider if you only want too push things by a rounding error the way I did in the original rules for a piracy campaign …. system geography

    If you have fairly massive objects out in the oort cloud region of both systems as we now know exist, they can be the discharge points giving you a slight (rounding error level) increase on the 7.7 limit.

    For example traveling between 2 bodies in Pluto’s orbit (over 5 light hours out) around stars rather than measuring Sun > Sun gives you just over 0.001 LY. Sedna is about 0.015 LY out at aphelion so reaching a twin in the neighbouring star gets you a more significant 0.03 LY

    there are a few systems in the original NSL that are between 7.700 and 7.710 apart. IIRC my pirates used one in the latin finger to establish a base in an “unreachable” system (before GDW started adding tugs and backdoor etc to give players other ideas)

    1. The problem with that is that a Pluto-sized icy body won’t cut it for being a discharge point – an object with Pluto’s density (1880 kg/m³) needs to have a radius of over 1900 km to have a stutterwarp limit above it surface (Pluto’s radius is 1187 km).

      There’s no rules for how far you actually have to be above a surface to discharge – can you be 1 km above an airless iceball, or do you have to be 100 km above it? if you have to be 100 km above it then the minimum radius for a pluto-density iceball has to be 2100 km.

      Granted that’s not impossibly big, but given that’s nearly twice as large as any KBO we’ve found in our outer system it may be unlikely.

  4. Well dang !

    I just had a look at your stutterwarp spreadsheet which seems to show you need to be well below the surface (640km of 1187) to get 0.1g

    Hopefully the resolution of the on again/ off again idea of something reasonably big (near earth mass, not that niburu / planet x hokum) out there disturbing the orbits of sedna etc puts my idea back into the realms of the possible

    1. Running a quick simplification, it looks as if having your anchor mass made out of pure osmium lets you get it down to 3.5e20kg to have 0.1g at the surface. Anything less dense needs to be heavier and thus much bigger (required density scales with square root of mass). So a Ceres-sized lump of osmium will do it, but a Vesta-sized one won’t. If you go with more reasonable densities, 6e21 kg is the cutoff – which means a Pluto-sized iron body works, but none of the classical asteroids. (Except Pluto itself doesn’t, because it’s not made of iron, so it’s much less dense than it needs to be.) Looking at actual solar system bodies which fit the discharge parameters, it’s the modern planets (and the Sun itself) and nothing else.

      1. Yeah, but you’re not really likely to find lumps of pure osmium floating around in an asteroid belt :). A big iron asteroid is more likely, but even then we don’t know of any that are anywhere near big enough (Psyche is the largest known metallic asteroid at around 253 km diameter, and even with its high density of 6730 kg/m³ it’s not large enough to be able to discharge there (it’d need a radius of more like 535 km with that denisty).

        1. I think we’re coming to the same conclusion from opposite ends: you need to find something pretty substantial to serve as a discharge point, well beyond the scale of anything human-buildable. If there are such bodies in our own outer solar system, they’re occupying a narrow gap between “too small to be useful” and “so big we would have spotted them already”. The ideal thing to find would be a rogue planet.

          (I’m working on a jump map for another setting using Delaunay triangulation at the moment and that’s going quite well. Having known jump points does make many things simpler.)

          1. I think captured planets would be rare. Planets tossed out from the inner system (like the putative-but-increasingly-likely-looking Planet Nine) but now orbiting at KBO-Oort clouds distances could be common though. Though I guess the worldgen system would have to be modified to include the possibility of those.

  5. while looking at updating the realistic star data again, im surprised to see that contrary to the Hip listing which has very few binaries, the old quib that multi-star systems are normal is true, especially for larger stars. some of them are hundreds of AU apart and a few I’ve found so far have around a thousand AU

    to me these quirks of astrography and scenarios built around them are far more appealing than tugs or new tech based on the kind of tweaks listed above.

    I’ve always assumed to be some sort of paradigm shift in tantalum use was behind the massive ranges achieved by the (Medusa ?) eg the drive consumes tantalum as it goes to discharge the build-up while the ebers was just an unrevealed brown dwarf