General How does maneuver drive propel?

[whulorigan]

77 doesn't.
You get silly amounts of delta-V from the fuel, but not actually unlimited.
The "at least 288 turns" (48 hours flat-out, and handwaved to "you won't run out no matter how far you go") is an implicit handwave, because even if you wouldn't have used all 288 turns of full-power acceleration on some trips (small planets with small 100D radii), the fuel goes away anyhow...

Though it never was stated outright, a trip with sequential wilderness refueling at gas giants (origin, gas giant, jump, gas giant, destination) would easily exceed 48 hours total acceleration in the gas-giant/jump/gas giant portion. It's "enough" because the rules say it is, not because the fuel burn rate works out that way.

It's nice to see that the Old Terran Corporation Fiat^TM is still operating and building drive motors in the 57th Century . . .

 

[Spinward Flow]

Though it never was stated outright, a trip with sequential wilderness refueling at gas giants (origin, gas giant, jump, gas giant, destination) would easily exceed 48 hours total acceleration in the gas-giant/jump/gas giant portion. It's "enough" because the rules say it is, not because the fuel burn rate works out that way.

The trick with that pattern of maneuver is that you need to STOP ACCELERATING and just coast on inertia during transits. Basically you power down the maneuver drive and simply take longer to get to your destination.

Why hello Jet Propulsion Laboratory! Fancy meeting you here ...

Unfortunately, pausing acceleration before reaching the midpoint turnaround and delaying deceleration into rendezvous after the turnaround at the midpoint of the journey just makes the math for transits even more complicated and therefore annoying to have to deal with. Besides, under most circumstances, time a ship spends on maneuver drive is time that the operator(s) are not generating revenue for(!).

If time is money (and in transport services it most definitely IS!) then time spent maneuvering around is "time wasted" ... and because time is money that computes to being "money wasted" on the accounts ledger.

There are ways to finesse this point, but doing so increases the workload for both the Referee and the Players.

Is it better laziness through efficiency, or is it better efficiency through laziness? I can never remember.



Point being that "annoying math problems are annoying" and both Players AND Referees are ... motivated, shall we say ... to minimize the annoyance of needing to compute annoying bookkeeping questions, such as "How how much time and fuel needs to be expended to maneuver transit from HERE to THERE?" ... so that they can get on with the "fun stuff" of adventuring (and so on).

And thus, handwavium becomes the Solution Of Choice™ for sidestepping these kinds of logistical annoyances.



For anyone who has participated in a merchant starship campaign setting, riddle me this.
When during the course of that campaign play did the maneuver drive performance "become important" ...?

If the answer to the question comes back "only when we were attacked" then you'll begin to grasp the scope of the problem. When maneuver drive capacity becomes your DUMP STAT because "it doesn't really matter 99.99% of the time" then your campaign setting is obviously not doing enough maneuvering around in normal space (because the jump drive is all that matters, duh! ).

 

[Marcatlas]

In its second edition (1981). First edition had it, but with absolutely bonkers fuel burn rates that disregarded not just mass but also volume.

It's where the 10Td/Pn requirement originated. They kept the quantity while changing it's duration from "enough for 1 trip's accelerations / at least 288 combat turns*" to "enough for 4 weeks".

---------
* Context: you won't run out of fuel due to the detours of engaging in space combat.

No, the '81 PP fuel usage rate is detached from M drive usage. The PP uses the same amount of fuel in 4 weeks even if you ripped out the M Drive and just powered the ship's other systems

 

[Marcatlas]

77 doesn't.

Correct. '81 does.

 

[bookwyrm]

Everyone knows the nozzles on the backs of the ships are light bulbs tied to the throttle. The brighter the light, the faster the ship is accelerating.

It's like those 3rd brake lights we have, or turn signals...required equipment in civilized space so folks can see what it going on.

They're tapping their throttle to accelerate slower than you are. If you don't do the same, the nose of your ship is going to 'bump' the 'light bulbs' and the resulting damage is going to generate a lot of 'insurance paperwork'. Since you 'bumped' them, your insurance rates are going to get astronomically high.

 

[coliver988]

They're tapping their throttle to accelerate slower than you are. If you don't do the same, the nose of your ship is going to 'bump' the 'light bulbs' and the resulting damage is going to generate a lot of 'insurance paperwork'. Since you 'bumped' them, your insurance rates are going to get astronomically high.

bolded - are all starship insurance rates literally astronomical?

 

[Grav_Moped]

No, the '81 PP fuel usage rate is detached from M drive usage. The PP uses the same amount of fuel in 4 weeks even if you ripped out the M Drive and just powered the ship's other systems

I think I was unclear in my phrasing. '77 had it directly supporting only the M-drive, 81 didn't -- but it kept the same formula as the earlier version that did for backward compatibility, just redefined what the fuel did.

 

[Grav_Moped]

If the answer to the question comes back "only when we were attacked" then you'll begin to grasp the scope of the problem. When maneuver drive capacity becomes your DUMP STAT because "it doesn't really matter 99.99% of the time" then your campaign setting is obviously not doing enough maneuvering around in normal space (because the jump drive is all that matters, duh! ).

For the most part in LBB2 design, it can safely be the dump stat. Except when it can't. But LBB2's gonna LBB2...

The point about ballistic vs. brachistochrone trajectories is quite valid. If you can't simply burn/flip/burn due to fuel limits, you coast in the middle and the math gets slightly more complex -- and who needs that? Hence the handwave.

 

[Spinward Flow]

brachistochrone trajectories

Fun part is that we've now got computers (programs, online calculators, etc.) that actually CAN do the math for us ... and it's STILL too much of a hassle to deal with. { liberally apply handwavium until problem goes away }

 

[mike wightman]

A course on rocket science and orbital mechanics is well worth the effort to learn this stuff...

failing that Kerbal Space Program

 

[bookwyrm]

bolded - are all starship insurance rates literally astronomical?

I guess there are many factors to consider.

1. Financial Health of the owner.
2. Insurance Company.
3. Severity of damage.
4. How often the starship is damaged or stolen.
5. Different starships have different rates.
6. Private, Industrial, or Commercial use.
7. Age of the starship.
8. I'm sure there are other factors...

All it takes is one moment in time for a starships maneuver drive to propel it into possibly astronomical insurance rates.

 

[whartung]

Anecdotally, the fact that Insurance doesn't seem to come up except in passing suggest a) either there is no insurance at all or b) the charges are nominal enough to not be really noticed.

 

[coliver988]

Anecdotally, the fact that Insurance doesn't seem to come up except in passing suggest a) either there is no insurance at all or b) the charges are nominal enough to not be really noticed.

well, Traveller is sometimes known as accountants in space. Guess actuaries in space was a step too far?

 

[kilemall]

I figure it’s wrapped into the mortgage payment and payable to the bank only, on declaration of loss.

 

[whulorigan]

I figure it’s wrapped into the mortgage payment and payable to the bank only, on declaration of loss.

That is workable for ships with a mortgage. But what about ships owned outright?

 

[atpollard]

That is workable for ships with a mortgage. But what about ships owned outright?

Is there a requirement to insure a WATER ship with a three person crew operating as a tramp freighter among the Caribbean islands (or Indonesia)?
A bank holding a mortgage might want insurance, but is every small supply boat owned free and clear insured?

 

[aramis]

Mike, thanks for that! I started with CT early on, and that's where my thinking comes from. If fuel is consumed for thrust then there are limits, and limits are fine.

The amounts of fuel used in CT1e are no less handwavium; insufficient mass for any reasonable Ve (exhaust velocity).

 

[mike wightman]

100,000,000g scout ship throws out ~60g of fusion products per second to accelerate at 9.8m/s^2
The fusion product reaction mass would need to be ejected at ~17,000km/s, or ~0.06c

Now before you quibble over the mass, in 77 LBB:2 a starship ton was 1000kg. But let's assume the more reasonable mass of 1000,000,000g is used, the fusion exhaust would have to be moving at 0.6c.

That's an engineering challenge for a TL9+ culture with fusion power and gravitics to solve.

 

[kilemall]

100,000,000g scout ship throws out ~60g of fusion products per second to accelerate at 9.8m/s^2
The fusion product reaction mass would need to be ejected at ~17,000km/s, or ~0.06c

Now before you quibble over the mass, in 77 LBB:2 a starship ton was 1000kg. But let's assume the more reasonable mass of 1000,000,000g is used, the fusion exhaust would have to be moving at 0.6c.

That's an engineering challenge for a TL9+ culture with fusion power and gravitics to solve.

I assume a PA accelerator/mass driver was involved.

 

[AnotherDilbert]

Now before you quibble over the mass, in 77 LBB:2 a starship ton was 1000kg. But let's assume the more reasonable mass of 1000,000,000g is used, the fusion exhaust would have to be moving at 0.6c.

That's an engineering challenge for a TL9+ culture with fusion power and gravitics to solve.

As we enter relativistic velocities, momentum is not linearly proportional to velocity.

What is the energy consumed by accelerating the propellant to relativistic velocity? Does your power plant produce that much?

60 g = 0.06 kg per second to 0.5 c is
e_k ≈ ½mv²𝛾 = ½ × 0.06 × (150×10⁶)² × 1.15 ≈ 7.8 × 10¹⁴ J/s [=W]

Does the Scout power plant produce a PW = 1000 TW = 1 000 000 GW = 1 000 000 000 MW?


Terra currently has a production capacity of something like 25 TW = 0.025 PW.