High-Burn Thrusters

[locarno24]

Just reading Scoundrel (nice sourcebook) and came across the High-Burn Thruster. Which seems an interesting bit of kit but also somewhat off; as in the described rules seem completely at odds with the description in the Buccaneer-class Blockade Runner, which has one fitted.

P.88 - High-Burn Thruster Rules
~ Essentially replaces the M-Drive for the duration of use
~ Takes up 20% of the size of a 'proper' M-Drive of the same power
~ Requires 25% of the volume of the drive in fuel for 1 hour's use
~ Max 1 hour use followed by 1 hour cooldown

P.91 - Buccaneer-class
~ Lists the thruster as 'thrust +3'
~ Same size as main M-Drive (of same power)
~ Using 20 dTons of fuel (approximately 200% volume) per hour
~ Description implies at least 2 hour continuous burn

Which way is it supposed to work? It wouldn't irk so much if the two weren't within three pages of one another...

 

[Rikki Tikki Traveller]

I would go with rules as written, not the example.

Unfortunately, there seems to be a LOT of issues with a lot of the designs. Either they were done using an earlier version of the rules, or the designer just misunderstood or misapplied the rules.

 

[locarno24]

Fair enough.

I was looking at the book with eyes to my Pirates of Drinax players commissioning some custom ships for entirely legitimate purposes.

For purely legal reasons, being able to kick it up to a 6G acceleration for an hour without occupying much space seems like an attractive option.

The thing I was trying to figure out (and where the example was confusing me, for I am but a bear of little brain) was if there was any way to give a (non small-craft) ship better than a 6G burn, even temporarily.

 

[Rikki Tikki Traveller]

Going over 6Gs on a non-small craft is entirely up the Referee. The rules as written don't allow it (the tables stop at 6), but there are no specific RULES saying you can't; just the tables.

Personally, I have ALWAYS allowed more than 6Gs, just keep the progression going. Usually size limitations kick in on anything other than a spaceship (non-Jump) and I personally don't have a problem with non-starships being really agile compared to their interstellar cousins.

 

[AndrewW]

While the rules don't technically allow it. One could figure on being able to exceed 6g's on larger hulls for the short term, just not sustained.

 

[SSWarlock]

And note that the rules don't state whether or not the acceleration from the hi-g thrusters is compensated for by the inertial compensation field/generators/handwave that compensates for the acceleration provided by a ship's regular M-drive. IMTU, I've ruled the thruster G acceleration is not compensated for but I'd be interested in hearing how others treat it and why.

 

[DickTurpin]

It looks to me like the High-Burn Thrusters were originally based on the Reaction Drive from High Guard. Reaction Drives are the same size as gravitic drives so that could be where he tonnage came from, they would also require 30 tons of fuel/hour to give a 400 ton ship like the Blockade Runner 3Gs of thrust which could be where the 60 tons for two hours came from (as listed in the ship description paragraph, I have no idea how they came up with the "3 hours fuel" written below in the detailed description).

From the High-Burn Thruster description I expect that it would actually require 2.75 tons of the expensive (10,000 Cr./ton) "Thruster Fuel" required for the high-burn thruster rather than the standard hydrogen power plant fuel used in a HG Reaction Drive. This figure assumes that the word "drive" in the second paragraph of the description refers to the mass of the M-Drive equivalent as opposed to the tonnage of the H-B Thruster itself, which is referred to as "thruster" everywhere else. If it is supposed to be 25% of the thruster tonnage it would only require 0.55 tons/hour which seems like way too little.

The only way to get two hours of continuous burn from an H-BT would be to mount two of them and light off the second one when the first burns out. I suppose that they could be fired at the same time but I would favor the uncompensated thrust ruling to keep things from getting out of control. Two hours at 3G would be bad enough; very few people could take 6Gs for an hour at a time without losing consciousness (or worse).

 

[SSWarlock]

Resurrecting this thread with a question..can high-burn thrusters take advantage of advanced TLs to gain upgrades listed in Book 2: High Guard? Upgrades like decreased displacement tonnage, Resistant design, Easy To Repair, etc.

By the way, I believe the OP was incorrect in stating that an HBT "..essentially replaces the M-Drive for the duration of use". The HBT acceleration is in addition to the regular M-Drive acceleration; hence, the description of the HBT on page 88 of Book 6: Scoundrel as giving "..a temporary boost to a ship." and the example design on page 91 of the same book. So, yes, you can have up to 12Gs of constant acceleration for a solid hour on a larger-than-smallcraft vessel if the vessel mounts a standard 6G-capable M-drive..which, as Mr. Turpin pointed out above, is rather rough on the crew since it may be the HBT-based acceleration isn't covered by the ship's inertial compensation system.

[Edit: anyone know the base TL of a HBT?]

 

[locarno24]

Just use the same tech level (per rating) given for normal drives, I guess. Certainly the same rules about higher tech levels miniaturizing them should apply; it is, essentially, a second M-drive (albeit one designed for short-term use), so why would the standard rules not apply?

We use the same principles for emergency power plants - TL15+ ones should be more compact.

 

[F33D]

Two hours at 3G would be bad enough; very few people could take 6Gs for an hour at a time without losing consciousness (or worse).

You'd most likely be dead. Most people would black out after a few seconds of 6 G.

 

[alex_greene]

If your vessel has been retrofitted for this, the inertial dampers likely won't be set to cope with the acceleration; and you'd need to make an Engineering roll to determine whether or not the ship's inertial dampers can be upgraded - and if so, how much it would cost.

It is likely that ships built with the thrusters from the drawing board stage could have inertial dampers to handle the extra burns; or they might not, depending on the design philosophy of the shipbuilders and, perhaps, costs.

It would make for a great adventure if the ship's Engineer found that the ship had been built with the intent of installing a HBT, but they never got around to fitting either it or the high grade inertial dampers. The quest to acquire and fit the technology could take up several adventures, dabbling in trading to raise the funds, seeking out Patrons willing to offer them the requisite parts (if they will undertake a mission for them, of course) and so on.

 

[SSWarlock]

A study of extreme acceleration/deceleration on the human body was conducted in the 1950s. The results were not widely known at that time but were accidentally rediscovered in April 29th, 2001 on a public racetrack (oopsie!). A paper on both events can be found at http://csel.eng.ohio-state.edu/voshell/gforce.pdf

Quite an interesting read. Especially since MongTrav allows the design of a 30-ton small craft with an M-drive capable of 16Gs.

 

[locarno24]

As noted, though, the question is always what proportion of that is actually 'felt' by the crew - any acceleration produced by a gravetic M-Drive doesn't count as the ship's essentially in free-fall.

 

[SSWarlock]

As noted, though, the question is always what proportion of that is actually 'felt' by the crew - any acceleration produced by a gravetic M-Drive doesn't count as the ship's essentially in free-fall.

Exactly. So a 30-ton ship can be designed as a great scout by loading it up with the best sensors that will fit, stealth, and engineering that supports a 16G M-drive with a 2G-capable HBT. That way, it can get out of trouble faster as it can get into it. After all, nothing's going to hit something that can scream away faster than a missile while applying, say, 7Gs to evading incoming fire.

 

[F33D]

As noted, though, the question is always what proportion of that is actually 'felt' by the crew - any acceleration produced by a gravetic M-Drive doesn't count as the ship's essentially in free-fall.

Exactly. So a 30-ton ship can be designed as a great scout by loading it up with the best sensors that will fit, stealth, and engineering that supports a 16G M-drive with a 2G-capable HBT. That way, it can get out of trouble faster as it can get into it. After all, nothing's going to hit something that can scream away faster than a missile while applying, say, 7Gs to evading incoming fire.

Quite interesting. Has anyone here designed a 30 ton 16G craft? I started long ago but it didn't look as though there was tonnage needed for anything much more than than PP, fuel + engines.

 

[SSWarlock]

Quite interesting. Has anyone here designed a 30 ton 16G craft? I started long ago but it didn't look as though there was tonnage needed for anything much more than than PP, fuel + engines.

Funny you should ask.

I did one just to see how far I could push the envelope. It pretty much can't include any useful level of armor or weaponry but it did have a Model 6 computer and enhanced signal processing to counteract the effects of the civilian basic sensor package. Definitely a workable design.

 

[locarno24]

There isn't below TL15. At TL15, you save 25% of the volume of that Fusion sZ, as well as 25% of the volume of the Manouvre sZ. Put those together, and you've got just enough space for a cockpit, 24 hrs fuel, a turret and a sensor suite.

 

[F33D]

Quite interesting. Has anyone here designed a 30 ton 16G craft? I started long ago but it didn't look as though there was tonnage needed for anything much more than than PP, fuel + engines.

Funny you should ask.

I did one just to see how far I could push the envelope. It pretty much can't include any useful level of armor or weaponry but it did have a Model 6 computer and enhanced signal processing to counteract the effects of the civilian basic sensor package. Definitely a workable design.

Ah, okay it can be done. Not particularly viable but doable.

 

[locarno24]

as well as 25% of the volume of the Manouvre sZ

Correction - I'm a cretin.
You can't miniaturize a thrust-16 drive below TL silly. You can save quite a bit of space with a reaction drive - but you really have to have a plan for what you're doing with the craft for such a short endurance to be useful.

Essentially, for racers or really, really specialist craft, might be useful. Not so much for anyone else.

 

[SSWarlock]

You can't miniaturize a thrust-16 drive below TL silly.

Eh? I'm not sure what you mean by this. Could you explain please? Did I miss a rule somewhere affecting what can and can't be miniaturized?

You can save quite a bit of space with a reaction drive - but you really have to have a plan for what you're doing with the craft for such a short endurance to be useful.

Essentially, for racers or really, really specialist craft, might be useful. Not so much for anyone else.

Yeah, pretty much. The fast scout I designed had a cockpit, no weapons, no cargo room to speak of, and only 12 hours' worth of fuel. So its usefulness is extremely limited. Hmmmm.

:shock:

:idea:

I wonder how it would perform if it was redesigned as a remotely operated platform that manages target tracking updates for missile flights. Kind of like the Ghost Rider platform in the Honor Harrington books.

*scrambles to pour over the High Guard and Trillion Credit Squadron books for target tracking rules*