CT Only: Book 2, power plant fuel requirements

[Spinward Flow]

It directly contradicts the powering down rules

How is "spend extra fuel on reaction maneuvering" a contradiction of the powering down rule (under which you would presumably be performing minimal reactionless maneuvering anyway)?

Changing the X axis parameter on the graph does not impact the Y axis parameter on that graph.
You might change the "area" described by a rectangle between (0,0) and the placement of (x,y) on the graph, altering a ship's overall fuel endurance profile when using fuel for reaction thrust to maneuver, but that doesn't "impact" the powering down rule at all or how the powering down rule functions (or when you would want to use it).

E.g.: A 5000 Dt PP-1 LBB2 ship requires a 10 Dt fuel tank.

Note that under the modifications to the fuel rule proposed above, that would no longer be the case.

Your "5000 Dt PP-1 LBB2 ship" would require a 50 Dt fuel tank for 4 weeks of power plant operation plus reactionless maneuver capability within 1000 diameters of a gravity well. If you wanted to take that same ship beyond 1000 diameters and would therefore need to rely on HEPlaR reaction maneuvering capacity (as stipulated above) the ship would need to expend 2.5 Dt of fuel per day to maneuver beyond 1000 diameters. The HEPlaR reaction fuel could be drawn from the base 50 Dt allocation, reducing maximum endurance of power plant operation ... OR ... additional fuel tankage could be specified as part of the design and/or retrofitted after construction (demountable tanks, collapsible tanks, etc.) if needed to supply additional fuel reserves for use as reaction maneuver fuel beyond 1000 diameters for considerable durations.

Remember, MOST craft aren't going to spend a whole lot of their time in normal space beyond 1000 diameters of a gravity well. Some will ... such as Belters, Scouts, the occasional Lab Ship and the like either prospecting or conducting research of some kind, as well as some System Defense Boats on patrols ... but most craft will not be operated in such a way as to need extensive reaction mass for continuous acceleration beyond 1000 diameters of a gravity well.

In practical terms, most starships will not need more than about a 7-8 day HEPlaR reaction maneuvering fuel reserve under most circumstances simply because it would be faster to micro-jump (stay in same hex, but consume fuel as if performing a jump-1) a distance that would take 8 days to maneuver in normal space within a system.

Fully fueled starships with Jump-1 and 2 parsecs of range could thus micro-jump to the Oort Cloud (well beyond 1000 diameters of anything), operate on HEPlaR reaction maneuvering fuel reserve except when "close" to a rendezvous with an object for prospecting, research, surveying work and still have sufficient fuel remaining to micro-jump back into the closer orbits to refuel and resupply safely. Such starships would presumably want to have a larger fuel fraction available for extended HEPlaR reaction maneuvering under such mission profile conditions, altering their fuel demands relative to those of a "core system" design starship that spends almost all of its time within 1000 diameters of gravity wells operating on reactionless maneuver thrust electrically driven by fusion power plant EP output alone (no extra fuel required to maneuver).

Interplanetary Travel Distance by Time and Acceleration
There's a reason why I published this reference.



When the paradigm changes and you don't alter your assumptions to match the changes in the paradigm you are extremely susceptible to drawing the WRONG conclusions with extreme confidence.

 

[AnotherDilbert]

How is "spend extra fuel on reaction maneuvering" a contradiction of the powering down rule (under which you would presumably be performing minimal reactionless maneuvering anyway)?

I was commenting the Beltstrike rules.

 

[whartung]

You need fuel to run the power plant to produce power for the M-drive, as usual.

Correct, there's nothing to suggest the fuel used for Maneuver was used for reaction mass (and clearly, it wasn't) any more than the diesel fuel in locomotives isn't used for reaction mass.

 

[kilemall]

I have another fuel use paradigm for the OP to consider.

Fuel use as heat expulsion mechanism.

The rear 'thrusters' are less rockets and more exhaust stacks.

 

[Spinward Flow]

Fuel use as heat expulsion mechanism.

The rear 'thrusters' are less rockets and more exhaust stacks.

Already factored into power plant fuel consumption requirements.

 

[BlackBat242]

Just wondering why there is discussion of HEPlaR drives in a thread specifically titled CT only!

 

[Spinward Flow]

Just wondering why there is discussion of HEPlaR drives in a thread specifically titled CT only!

Easiest touchstone reference point for the difference between reaction and reactionless thrust maneuver drives.
CT doesn't make any distinction between the two, but I figure it's useful for thinking about the different contexts of maneuver drive use.

Kind of like how subsonic and supersonic flight are different aerodynamic performance contexts, even for aircraft that are perfectly capable of doing both.

 

[HanleyTucks]

Just wondering why there is discussion of HEPlaR drives in a thread specifically titled CT only!

CT books 1-3 make no mention of the nature of the power plants or drives, except noting the rate of fuel use in the context of it flowing through as reaction mass. There's also no artificial gravity mentioned.

The things could be chemical (hard to imagine how, but it's not mentioned), fission, fusion - it's not mentioned. There are tech level charts in Book 3, however mentioning that "fission" or "fusion" exist does not mean they are available for a particular application. After all, 80 years since the first fission reactor, we still don't have one in our backyard, and not on spacecraft, either.

In later books they get more specific. But in Books 1-3, it's just "power plant" and "drive." If you want HEPlaR, then that's easy to imagine in Classic Traveller. In fact, I would have as much a right to complain that CT discussions assume artificial gravity.

 

[BlackBat242]

HEPlaR is a specific rules/tech item first introduced in The New Era edition of Traveller.

Thus, it does not belong in a "CT Only" discussion thread.

And no, it is NOT "a touchstone" to someone who has not, and likely never will, even read TNE rules... much less actually own them.

For myself, and anyone seeking a "CT Only" tech discussion it is a jarring intrusion of non-CT material.


Call it something else, if you have to have a name in order to be able to discuss a reaction-based thrust system.

 

[Spinward Flow]

HEPlaR is a specific rules/tech item first introduced in The New Era edition of Traveller.

The name for it may first be given there.
The concept however is not "new" to TNE.

It's a plasma rocket.
It provides reaction thrust yielding acceleration.

At worst, it's a kind of rocket defined in more detail after CT.
The whole point of providing a link to the wiki page on the subject was to show that I wasn't making it up whole cloth out of nothing at all.

And as I've noted elsewhere ... CT Beltstrike had extra fuel consumption for maneuvering long term under maneuver drive above and beyond mere power plant consumption (presumably for reaction rocket thrust). Beltstrike didn't name it as HEPlaR but the function was pretty much exactly the same.

Six of one, half a dozen of another ... a rose by any other name ...

Need I go on?

 

[aramis]

Need I go on?

If you do, you lose your posting privileges.
Private warnings haven't been effective, so it's a move to public ones.

 

[mike wightman]

The reason why HEPlaR has come up in a CT discussion is that the CT m-drive is a fusion rocket of some sort and HEPLaR is the closest well defined technology.

 

[kilemall]

HG edition 1 had that M-drive as plasma torch weapon, so there is that CT reference.

 

[Grav_Moped]

So, if I'm understanding this correctly:
1. When discussing CT maneuver drives in the context of CT, you cannot declare that they're "HEPLaR" because that term didn't exist when CT was written, and because the characteristics of that drive system as described in TNE (size, cost, fuel use) are not identical to those of LBB2 maneuver drives.
2. Presumably when discussing "HEPLaR" drives in the context of TNE, you could say that they're similar to LBB2 '77 maneuver drives in that they're both reaction motors of some sort (though this isn't necessarily the case even for LBB2 '77 as noted below), and fusion or near-fusion is likely involved. You still can't say that LBB2 '77 maneuver drives are literally "HEPLaR" drives, I think.
3. LBB2 '77 drives were never explicitly stated to be reaction motors, though it would be an easy inference to make if you wanted to.
4. LBB5 '79 drives were explicitly reaction motors (and by inclusion, this applied to LBB2 '77 drives as well) because of the weaponized exhaust rule. That said, LBB 5 fuel use rates did not reflect this.
5. LBB5 '80 retconned maneuver drives into grav drives or reactionless thrusters of some sort, precisely to eliminate exhaust weaponization, and by inclusion did the same to LBB2 '77 drives.
6. LBB2 '81 officially made the same retcon for LBB2 drives.

 

[Spinward Flow]

CT Beltstrike ©1984 also used and defined reaction fuel rules for maneuvering as one of the consumables that could prompt an early "return to base" condition ending a belter prospecting run due to lack of consumables reserves.

 

[mike wightman]

5 - LBB5 80 doesn't refer to the m-drive as grav drives or reactionless.
6 - LBB2 81 also doesn't mention m-drives being grav drives or reactionless.

Found another reference to reaction drives - the S7 Gazelle is described as having two model 16 impulse maneuver units.

 

[HanleyTucks]

In my experience, these sorts of semantic quibbles do not attract newbies to a game. I find it's better to be open and accepting.

 

[AnotherDilbert]

CT Beltstrike ©1984 also used and defined reaction fuel rules for maneuvering as one of the consumables that could prompt an early "return to base" condition ending a belter prospecting run due to lack of consumables reserves.

Beltstrike does not mention propellant or reaction fuel at all, just "fuel".

It says, just like LBB2 and LBB5, that spacecraft use fuel to manoeuvre without specifying how.
Just like a car: It uses fuel to manoeuvre, but that does not make it rocket powered.

Beltstrike, p5, "Expedition Duration":

Fuel Is the other factor. Fuel use during a prospecting and mining expedition is significantly lower than in normal operations, since constant acceleration is rarely undertaken.
The fuel consumption table on page 11 shows the requirements of various types of maneuvering in terms of fuel use per hundred tons of ship. Basic power is used at all times, including when maneuvering. Every maneuver (matching course with an asteroid, for instance) uses a t least one hour's fuel at the 1G rate. The referee and/or players should keep track of a ship's fuel supples: the ship should not be permitted to run out of fuel. It is possible to refuel by locating ice chunks, skimming gas giants, etc.

 

[AnotherDilbert]

5 - LBB5 80 doesn't refer to the m-drive as grav drives or reactionless.
6 - LBB2 81 also doesn't mention m-drives being grav drives or reactionless.

Agreed, it just states that M-drives produce thrust using power from the power plant, but without using any noticeable amount of fuel or propellant. Doesn't sound like a rocket to me...

LBB5'80, p17, ¶2:

MOVEMENT
Starships move through ordinary space using maneuver drives as described in Book 2, page 1 under Interplanetary Travel. Power for the maneuver drives is provided by the starship's power plant, which must have a rating equal to or exceeding the drive number of the maneuver drive. Tech level requirements for maneuver drives are imposed to cover the grav plates integral to most ship decks, and which allow high-G maneuvers while interior G-fields remain normal. Fuel consumption for maneuver drives is inconsequential, and is assumed to be part of the power plant consumption, regardless of the degree of maneuver undertaken.

Found another reference to reaction drives - the S7 Gazelle is described as having two model 16 impulse maneuver units.

And what is an "impulse maneuver unit"? Or any of the rest of the technobabble?
S7, p32, text box in graphic:

Range: Unlimited maneuver. One jump 4. 100 days.
Engineering: Two Triptic Halonic Fusion power plants coupled to one IDC FarDrive jump unit and two model 16 impulse maneuver units.

Note that whatever it is, it does not use enough fuel or propellant to limit acceleration duration.

 

[whulorigan]

And what is an "impulse maneuver unit"? Or any of the rest of the technobabble?

"Impulse" is a technical term in Physics; it simply means a change in momentum. Any drive that changes a craft's momentum would be an "Impulse Drive", regardless of how it is accomplished.

(I am fairly sure the S7 Gazelle fluff-text lifted the term from ST:TOS, though, where "Auxiliary Impulse Engine" is used in the same context as a conventional drive, contrasted to the more esoteric "Space-Warp" Drive).