Crashing ships as weapons
- Thread starter Adam Dray
- Start date
Yeah, Barnard's Star (1.8 pc from Sol) has a relative velocity difference of 142 km/s. Wolf 424 (4.4 pc from Sol) has a relative velocity difference of 555 km/s. Those are pretty big differences!
No, we are not - the energy requirement puts a nice mechanic of diminishing returns on prolonged acceleration. And it's even solid physics (safe for the reactionless part).
I think part of the problem is that everyone keeps referring to the M-Drive (or "Thruster Plate") as "Reactionless". To my knowledge, only under MT/DGP:SOM is it explicitly "Reactionless" 1.
1 - DGP:SOM describes the Thruster Plate as being based on the Strong Nuclear Force, and employing some type of interaction that causes the plate to "push-off of itself". This interpretation was not carried forward into successive editions of Traveller.
CT post-1981 is rather ambiguous on the nature of the M-Drive (CT-era DGP considered it a gravitic-based system).
Both T4 & T5 explicitly describe the M-Drive as employing a gravitic-based interaction. Its thrust-efficiency also drops off to 1.00% beyond 1000 diameters under these rulesets.
The reason that is significant is that in any given star system there are plenty of gravitating bodies to react against employing a gravitic-based system, so it is not necessarily a "reactionless" system, any more than a NASA probe utilizing a gravitational slingshot or gravitational braking maneuver is a reactionless interaction. It is just that the gravitating bodies that the vessel is interacting with are so huge compared to the vessel itself, that the momentum change of the bodies in the star system are unmeasurably small.
So is part of the mechanism of the M-Drive (however it actually works) picking up momentum from other bodies in the system, which in reaction lose an equivalent amount of momentum? The power-plant only needs to power the M-Drive to do whatever it does. It doesn't have to entirely account for all of the momentum change - part of that can come from the bodies in the star system.
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So you'd propose the acceleration rates basically just work in-system, and rapidly drop as you leave the relative vicinity of planetary bodies? This could work, too, though STL ships that travel at significant fractions of the speed of light are actually quite common throughout Traveller canon....
Edit: But even using a planet as your reaction mass, minium energy requirements apply...
Edit: But even using a planet as your reaction mass, minium energy requirements apply...
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That has always been my interpretation. T4 & T5 seem to suggest that there is also some quantum-level interaction within the system that causes it to abruptly fall off at roughly the 1000 diameter limit (although game-wise, I assume that is a simplification so that the math doesn't become something that only physicists can handle.
)In T5 the drive is a highly focused gravitic-based Drive called NAFAL ("Not-As-Fast-As Light") that will operate out to about 1/8 light year from a star-system, with the sacrifice that no lateral motion can be produced by the drive - it is entirely focused along the drive-axis. Beyond 1/8 lightyear the efficiency drops off to ~1.00%.
The irony of your statement (which you seemingly acknowledge) makes me chuckle.
you used handwavium territory to accept the drive in the first place, and the energy requirements for the handwavium violate known physics, but placing an "addenda" that the way the reactionless drive works has limits breaks down the process of handwavium in the first place?
*chuckle*
House rules are attempts to fix written rules - and anyone who has a problem with Near C rocks (as the undying thread/concept has been justly named) with the rules as written, can either ignore the issue (as it has been ignored since day one of the rules published) or they can try to fix it themselves, or they can wait for Marc and company to fix it.
T5 has a lot of potential changes, a lot of potential fixes (different drives, different jump drive configurations etc) that T5's relationship to old rules is an interesting one. Does one stick to the older material, or use newer material that have implications for major changes? Does one play T5 as written, or continue to play MgT or GT, or MT, or CT or what have you?
Either way, I don't champion any solution one way or another...
I'm so used to fixing rules I don't like, and know that the fix is simple. As a GM, it is YOUR game being presented to your players. Fifity years from now, no one is going to remember a single thing I've written on any Traveller Mailing list or forum or what have you. I have no legacy to build or defend, and in the end...
Do as you will.
Gold medal post! I'm filing this one away in my save file.
555km/s is ~15.5 hrs of acceleration at 1G. So, part of the astrogation problem is to not just maneuver to 100Ds at the originating planet, but to prepare the ships vector for efficient navigation at the destination. The ship could burn 15.5 hrs in the first system before jumping in order to catch up to the destination system. Or, they can do the burn when they get there, or any mix in the middle.
The multi-jump acceleration scenario I posited was specifically designed around this aspect of the maneuver drives operation.
While I'm glad to amuse you in some kind of condescending way, you're missing the point. I generally want to reduce the hand-waving of science as much as possible. Blithely adding more unbelievable stuff on top of other unbelievable stuff doesn't make it better, or even leave it just as bad as it was. It's just more unbelievable. A thread like this is about understanding implications of science in my science fiction, not hand-waving it away with nary a care. Might as well include magic then, too, quoi?
I don't really accept the reactionless drive. Lots of people in this thread do, but I don't really like it.
My own Traveller games tend to avoid reactionless thrust drives in the first place. They use reaction drives, or (reactionless) gravitics, or something akin to stutterwarp for STL travel, with all the consequences (that I can think of) of the science I'm playing with. Indeed, "consequences of science" are the reason I play science-fiction games in the first place. Your mileage may vary, but if it does, this thread might not be for you.
I'm happy to imagine new rules of physics that empower mankind to travel the stars, but I want to look at all the implications of those physics, understand the limitations, and try to predict the social outcomes that result of new technology.
If you want to arbitrarily cap reactionless drives at 0.1c, I want to understand the justification for it. What science might cause that? I can think of only two absolute speed limits in the universe: 0°K and c. Making up a new one requires new understanding of science and it should be at least somewhat credible.
I really believe anyone who wants reactionless thrusters in their game should think about the above. It is inherently logical, uses real-world physics and would likely describe the way a real reactionless drive, should it ever be invented, would work in terms of power consumption.
I am a bit astonished this does not resonate more. (Not just because making that spreadsheet was fun...
)That my amusement was seen as condenscending was not my intent. I'm also easily amused when people discuss how many angels can dance on a pinhead if it is an article of faith that angels don't exist, or how spells work in a world where magic works, when one doesn't believe in magic per se.
As pointed out, how gravitics work, or any other handwavium technology works, is clearly "magic". Either science hasn't the clue on how to bring about the technology in question, or there is in fact, no basis for the technology (psionics would be a similar point of contention). That having been said?
One could EASILY incorporate the 10% light speed limitation saying that once that velocity is reached, the field effect that grabs gravitrons won't bite at all. The limit once hit, destroys the gravitic field's ability to even exist. It doesn't break suspension of disbelief, nor does it even really fall any further into the realms of science fantasy. It simply uses the same license for creation of an effect that the original author who wrote how Maneuver drives/plates work.
In fact, if I recall correctly despite my age - there was even speculation that the fuel required to power up the maneuver drives were expelled as reaction, before it was decided that it wasn't the case (trying to recall the late and unlamented Traveller Mailing list contents is an exercise in futility to be sure!).
In any event, I harbor no ill will towards anyone when it comes to Traveller stuff these days, nor do I consider my view to be the ONLY enlightened view. So, rest assured, I do NOT ever have the ability to think my views are superior to everyone else's. And if I'm amused, it is at the fact that I'm being asked to believe in gravitronic technology that doesn't exist today, and be told that any limits placed on a fictional technology is unrealistic. That's like asking how many ackatrons can rotate at light speed around the krackatronic field generated by a muon. (to throw gobblygook into this!).
On that note, and the fact that a Moderator had to intervene in this, makes me know, not guess, my welcome here is strained...
As pointed out, how gravitics work, or any other handwavium technology works, is clearly "magic". Either science hasn't the clue on how to bring about the technology in question, or there is in fact, no basis for the technology (psionics would be a similar point of contention). That having been said?
One could EASILY incorporate the 10% light speed limitation saying that once that velocity is reached, the field effect that grabs gravitrons won't bite at all. The limit once hit, destroys the gravitic field's ability to even exist. It doesn't break suspension of disbelief, nor does it even really fall any further into the realms of science fantasy. It simply uses the same license for creation of an effect that the original author who wrote how Maneuver drives/plates work.
In fact, if I recall correctly despite my age - there was even speculation that the fuel required to power up the maneuver drives were expelled as reaction, before it was decided that it wasn't the case (trying to recall the late and unlamented Traveller Mailing list contents is an exercise in futility to be sure!).
In any event, I harbor no ill will towards anyone when it comes to Traveller stuff these days, nor do I consider my view to be the ONLY enlightened view. So, rest assured, I do NOT ever have the ability to think my views are superior to everyone else's. And if I'm amused, it is at the fact that I'm being asked to believe in gravitronic technology that doesn't exist today, and be told that any limits placed on a fictional technology is unrealistic. That's like asking how many ackatrons can rotate at light speed around the krackatronic field generated by a muon. (to throw gobblygook into this!).
On that note, and the fact that a Moderator had to intervene in this, makes me know, not guess, my welcome here is strained...
That's really interesting.
So call an Earthlike diameter 13,000 km. 1000 diameters is 13,000,000 km, or just 0.87 AU.
Anyone want to do the math to determine relative velocity attained at 5G in 13 million km? Check my math.
s = 1/2 ( a t^2 )
13,000,000 = (0.5) (5)(9.8 / 1000 m/km) t^2
t = sqrt(13,000,000 / 0.0245)
t = 23,035 seconds = 6.4 hours
vf - vi = a t, vi = 0
vf = a t
vf = 9.8 (m/s^2) * 23,035 s
vf = 1,128,715 m/s
c = 299,792,458 m/s
So final velocity = 0.3% the speed of light when the M-drive stops really adding to the velocity.
What I didn't do is the calculus required to account for the reduction of gravitic push as it diminishes from 100% at 0 diameters to 1% at 1000 diameters, as an inverse-square function of distance. That is, I assumed a constant 5G acceleration for the entire trip, which is not at all the case.
Basically, all of special relativity, right? Of course, so does FTL travel outside of very specific instances of closed, timelike loops.
That is about 900.000 m/s, which means an impact energy 4,5*10¹¹ J of per kg of ship. For comparison: Hiroshima bomb: 7.2*10¹³ J.
A ship travelling at anywhere near C would be severely damaged if not destroyed by an impact with even a relatively small particle - firing a cloud of sand into the path of the ship would break it up. Actually getting a starship up to that speed without vapourising it is probably the biggest single obstacle to such an endeavour.
Even if your ship could withstand micrometeorite impact at that speed, accelerating to near-C is also something quite hard to do discreetly. At a distance where you could do it without being noticed, even hitting a planet-sized target is not a trivial achievement. Guiding space probes today requires multiple course corrections.
If you tried it close enough to a planet to be accurate then it's likely to be quite obvious something's amiss. Burning to correct your course at that speed is also going to be obvious - there would be an obvious blue shift on the emission spectra and you would have to burn quite hard to make a correction relevant to a course at that speed.
There's also the engineering problem of developing and testing a guidance system that will actually work well enough at near-C speeds to hit a specific target. This may or may not be within the levels of skill available to a government, let alone a small militant group.
