TNE Only: FF&S Self-Contained Thrusters FC, Size Efficiency, FT, and Fuel Volume

[snrdg082102]

Hello all,

I can not get a handle on the FC, Size Efficiency, FT, and fuel volume details for the self-contained thrusters on page 70 of TNE FF&S.

FC: Fuel consumption, in tonnes, per hour, tonne of thrust. To determine volume in cubic meters, multiply by the volume of the fuel type. For solid rockets, simply pick a fuel mass. Divide the mass by the FC value. The result is thrust in tonne-hours. Select either thrust or duration, and the other is determined from that. For example, 18 tonnes of TL-6 SF rocket fuel could have 2 tonnes of thrust for one hour, 4 tones for 30 minutes, 1 tonne for two hours, or any combination desired, as limited by the maximum allowed thrust (MaxT column).

Size Efficiency: Solid fuel rockets with less than 500 kg of propellant (fuel) mass suffer from inefficient fuel combustion. To determine the fuel consumption inefficiency of a solid fuel rocket divide 500 by fuel mass in kilograms. The result is the final fuel use multiplier. Multiply the calculated fuel consumption of the engine by this number. However, any multiplier less than 1 is treated as 1 and any multiplier greater than 10 is treated as 10.

FT: Fuel type burned. Note that at TL7+, any thruster which burns hydrocarbon distillates (HCD) may be designed to burn liquid hydrogen (LHyd) at no cost or energy penalty (the penalty is the vastly greater volume needed by LHyd).

Fuel Volume: The volume of fuel (in cubic meters) used per hour per tonne of thrust is equal to the mass (in metric tonnes) consumed per hour per tonne of thrust divided by the density of the fuel as show below.

Hydrocarbon Distillates (HCD) Density: 1; Price: Cr250
Liquid Rocket Fuel (LRF) Density: 1; Price: Cr1000
Solid Rocket Fuel (SRF) Density: 1; Price: Cr2000
Hydrogen Rocket Fuel (HRF) Density: 0.3; Price: Cr1000
Liquid Hydrogen (Lhyd) Density: 0.07; Price: Cr35.

In fuel consumption to convert fuel consumption from tonnes/hr./tonnes of thrust you use the volume of the fuel type. To determine the fuel volume divide the mass (in metric tonnes) consumed per hour per tonne of thrust by the fuel density.

None of the above is making any sense to me. Can anyone provide me with an example of how the rules work?

 

[snrdg082102]

[FONT=arial,helvetica]Hello all,

Looks like I need to do something to get some help, so I'm, going to start with the HEPlaR and Thruster Plate Drives working my way through each type. I'm going to start from thrust needed to move the object at 1G.

Here goes my attempt with the HEPlaR Drive.

Per TNE FF&S p. 69 10 tonnes of thrust (Tht) is needed to accelerate an 1 displacement ton (TD) object at 1G.

To accelerate a 100 TD at 1G the required thrust = 10 x 100 x 1G = 1000 Tht.

A HEPlaR Drive generates 20 Tht per MW. To generate 1,000 Tht requires 1,000 ÷ 20 = 50 MW of input power. The heat exchanger/re-combustion chamber has a volume of 0.1 x 50 = 5 m3, a mass of (1 tonne/m3) of 5 tonnes, costs MCr0.001 x 50 MW = MCr0.05. When used by a spacecraft the HEPlaR Drive requires takes up 1,000 ÷ 200 =5 m2 of hull surface area. The drive's fuel consumption rate of liquid hydrogen is 0.25 x 50 = 12.5 m3/hr/MW.

The volume, mass, and price of the fuel I'm not really clear about, but here goes anyway. The HEPlaR drive's fuel volume, being in cubic meters already, is 12.5 m3 and costs Cr35 x 12.5 =Cr437.5 per TNE p. 70.

A HEPlaR Drive capable of generating 1,000 tonnes of thrust has the following specifications:

0.36 displacement tonnes, Mass of 5 tonnes, Volume of 5 m3, draws 50 MW from the power plant, on a spacecraft requires 5 m2 of hull surface, and costs MCr0.05.

12.5 m3 of liquid hydrogen is consumed per hour and costs Cr437.5.

I think that the 12.5 m3 of fuel takes up 12.5 m3 of hull volume. Unfortunately I'm not sure about the fuel's mass.

Have I gotten most of the HEPlaR drive design process down correctly?[/FONT]

 

[aramis]

[FONT=arial,helvetica]Hello all,

Looks like I need to do something to get some help, so I'm, going to start with the HEPlaR and Thruster Plate Drives working my way through each type. I'm going to start from thrust needed to move the object at 1G.

Here goes my attempt with the HEPlaR Drive.

Per TNE FF&S p. 69 10 tonnes of thrust (Tht) is needed to accelerate an 1 displacement ton (TD) object at 1G.

To accelerate a 100 TD at 1G the required thrust = 10 x 100 x 1G = 1000 Tht.

A HEPlaR Drive generates 20 Tht per MW. To generate 1,000 Tht requires 1,000 ÷ 20 = 50 MW of input power. The heat exchanger/re-combustion chamber has a volume of 0.1 x 50 = 5 m3, a mass of (1 tonne/m3) of 5 tonnes, costs MCr0.001 x 50 MW = MCr0.05. When used by a spacecraft the HEPlaR Drive requires takes up 1,000 ÷ 200 =5 m2 of hull surface area. The drive's fuel consumption rate of liquid hydrogen is 0.25 x 50 = 12.5 m3/hr/MW.

The volume, mass, and price of the fuel I'm not really clear about, but here goes anyway. The HEPlaR drive's fuel volume, being in cubic meters already, is 12.5 m3 and costs Cr35 x 12.5 =Cr437.5 per TNE p. 70.

A HEPlaR Drive capable of generating 1,000 tonnes of thrust has the following specifications:

0.36 displacement tonnes, Mass of 5 tonnes, Volume of 5 m3, draws 50 MW from the power plant, on a spacecraft requires 5 m2 of hull surface, and costs MCr0.05.

12.5 m3 of liquid hydrogen is consumed per hour and costs Cr437.5.

I think that the 12.5 m3 of fuel takes up 12.5 m3 of hull volume. Unfortunately I'm not sure about the fuel's mass.

Have I gotten most of the HEPlaR drive design process down correctly?[/FONT]

Without checking the books to be certain, it does look correct.

HEPlaR fuel is liquid hydrogen. around 0.07 tons per cubic meter (m³).

You might want to use m[sup]3[/sup] instead of m3, tho'... as m3 means "meters trebled" while m³ means cubic meters, and is generated with. m[sup]3[/sup]

 

[elbmc1969]

[FONT=arial,helvetica]
Looks like I need to do something to get some help, so I'm, going to start with the HEPlaR and Thruster Plate Drives working my way through each type.

Just to be clear, HePlaR and Thruster plates are not Self-Contained Thrusters. The extended quote in the OP generally doesn't apply to them.

However, if you look at the Fuel Volume table, you'll see that Liquid Hydrogen has a density of .07. Density is in tonnes per m³, so the mass is a mere .875 tonnes. (The real-world problem with liquid hydrogen is that is about as dense as styrofoam. Hydrogen is a very mass-efficient fuel, but it is terribly volume-inefficient. When you have to build more structure for your spacecraft to contain all of that volume, you also need more thrust to keep the acceleration constant ... Turns out to be a huge problem if you want to build hydrogen-powered cars--you have to give up trunk space, or seating, or just make the whole vehicle bigger.)

 

[snrdg082102]

Hello aramis,

Without checking the books to be certain, it does look correct.

HEPlaR fuel is liquid hydrogen. around 0.07 tons per cubic meter (m³).

You might want to use m[sup]3[/sup] instead of m3, tho'... as m3 means "meters trebled" while m³ means cubic meters, and is generated with. m[sup]3[/sup]

Thank-you for the reply, that my math appears right, with the exception of the fuel, and my apologies about the issue with cubic meters.

I noticed that I had miss spelled a couple of words and when I tried doing an edit in IE and Firefox the edit window was blank. I did a copy and paste of the page, made the changes and re-posted the comment. Unfortunately I did not proof the re-post which I should have done. I'll make sure next, that is if my memory doesn't fail me.

 

[snrdg082102]

Evening elbmc,

Thank you for the reply.

Just to be clear, HePlaR and Thruster plates are not Self-Contained Thrusters. The extended quote in the OP generally doesn't apply to them.

You are correct that HEPlaR and Thruster plates are not self-contained drive. I also offer my apologies for not being clear that I was starting with HEPlaR, then progressing to the self-contained thrusters, and the rest of the drives.

Actually, I needed to ensure I had the basic process down for one of the common drives for spacecraft.

However, if you look at the Fuel Volume table, you'll see that Liquid Hydrogen has a density of .07. Density is in tonnes per m³, so the mass is a mere .875 tonnes. (The real-world problem with liquid hydrogen is that is about as dense as styrofoam. Hydrogen is a very mass-efficient fuel, but it is terribly volume-inefficient. When you have to build more structure for your spacecraft to contain all of that volume, you also need more thrust to keep the acceleration constant ... Turns out to be a huge problem if you want to build hydrogen-powered cars--you have to give up trunk space, or seating, or just make the whole vehicle bigger.)

Thank-you again for checking my work. From your critique the Density Factor on the fuel table has two functions. When the fuel consumption is in m^3/hr/MW the Density Factor is used to determine mass. When fuel consumption is in tonnes/hr/tonnes of thrust the Denisty Factor is used to convert from tonnes to m^3 and then used to determine fuel mass.

I hope I'm on the right track with the above.

 

[snrdg082102]

Hello all,

TNE uses volume in displacement tonnes to calculate the amount of thrust to accelerate at 1G. To ensure the volume based thrust value is adequate once the total mass of a fully loaded, includes a full fuel load, spacecraft the total mass is divided by the hull volume in displacement tonnes. If the final mass is greater than 15 times volume displacement calculate acceleration based on the actual thrust-to-mass ratio. Divide the thrust in tonnes by the total hull mass which results in the actual acceleration in Gs. The resulting G number is rounded down to the nearest whole number.

A 100 displacement tonne hull and has a total mass of 1,550 metric tonnes. According to the TNE FF&S rules to accelerate the 100 displacement tonne to 1G require 10*100*1 = 1,000 tonnes of thrust. Per the check of the final mass in metric tonnes and displacement tonnes the mass is 1,550 metric tonnes ÷ 100 displacement tonnes = 15.5.

Since the total mass is 15.5 times that of the displacement tonnes the actual thrust-to-mass ratio is used to determine the acceleration in Gs.
1,000 tonnes of thrust ÷ 1,550 metric tonnes = 0.6452 G rounding down to 0.6G.

To get 1G acceleration from a 1,550 metric tonne hull per TNE FF&S requires 1 tonne of thrust per metric tonne of hull, which I believe means 1,550 tonnes of thrust.

A hull using a drive generating 1,000 tonnes of thrust has a final mass of 692 metric tonnes when fully loaded has an acceleration of 1000 ÷ 692 = 1.4451Gs or 1.4Gs or 1G depending on where one rounds down to.

Hopefully, I'm on the right track on the rules and if I am not where am I going wrong.

 

[aramis]

It looks like you're doing it right.

The nastiest bit of TNE is the iterations in craft calculations...

 

[snrdg082102]

Evening aramis,

It looks like you're doing it right.

The nastiest bit of TNE is the iterations in craft calculations...

I feel a bit better now that there is confirmation I'm on the right track. My first go round is to get the designs to work one time and then do the iterations.

Unfortunately, I have only done the HEPlaR and Thruster Plates. The reason I started with them is that both T4 Book 1 QSDS and Book 2 SSDS both have and they do not appear to match with T4 Book B FF&S. The HEPlaR Tables in T4 Book 2 and the re0written SSDS by David Golden match in the drive characteristics, but I'm not sure about the fuel data. T4 Book 1 I'm still trying to work through.

Thruster plates in T4 Book 2 match everything but price using TNE FF&S. Of course I'm thinking that I may be doing the price calculation wrong, but that will wait until I work my way through the self-contained thrusters, realistic drives, ion drives, and the Dean Drive.

Hopefully, I'll have the turbojet and turbofan thrusters ready in the next couple of days.

Thank you again for the help.

 

[aramis]

QSDS in Bk1 was bad; a replacement version was available for download at one point.
SSDS and QSDS-revised were both built from TNE FF&S 1, not T4 FF&S2. Minor revisions happened between FF&S 1 & 2.

 

[rancke]

QSDS in Bk1 was bad;

The official ship design system was bad, but it wasn't QSDS; Guy Garnett designed QSDS in response to the official system.

...
a replacement version was available for download at one point.

Still is.

(Link is to a pdf on the B.I.T.S. website).


Hans

 

[snrdg082102]

Morning aramis and rancke,

QSDS in Bk1 was bad; a replacement version was available for download at one point.
SSDS and QSDS-revised were both built from TNE FF&S 1, not T4 FF&S2. Minor revisions happened between FF&S 1 & 2.

T4 Book 1 and Book 2 design sequences both have download replacement versions that are, as rancke mentioned are on the BITS site, which started me off on going through T4 Book B FF&S and discovering that both sequences, thank you for the confirmation, appeared to be TNE FF&S based.

When I typed QSDS I thought I had also include 1.5e which is the revised version, apparently one of my revisions while typing the post erased that bit of information.

I have not gotten to far in either T4 Book 1 QSDS or QSDS 1.5e but what I have gone over doesn't appear to be too different. The biggest difference I see is that the written details and tables are located by each other. There are issues with the some of the numbers in to the tables when comparing them with TNE FF&S design requirements or for that matter with the material in T4 Book 2.

Of course the design sequences in T4 Book 1 and T4 Book 2 are plug-in systems with a limited number of options similar to what is in CT Book 2. T4 Book 1 appears to have fewer options for the "standard" designs or those in T4 Book 2, however I'll need to verify the revised design sequences before making a final judgment.

Thank you both for the replies.

 

[snrdg082102]

Here is a recap of the HEPlaR Drive and the specification for a TL-5 Turbojet.

A HEPlaR Drive with an output of 1,000 tonne of thrust requires 50 MW of input power, the heat exchanger/re-combustion chamber has a volume of 5m^3 or 0.36 displacement tons, masses 5 metric tonnes, when installed on spacecraft requires 5m^2 of hull surface area, and costs MCr0.05.

The drive requires 12.50 m^3 of liquid hydrogen (LHyd) per hour per MW, or 0.89 displacement tons, masses 0.88 metric tonnes, at a cost of Cr437.5

Finally I'm getting to the self-contained thrusters:

A TL-5 Turbojet with an output of 6 tonnes of thrust requires 2 m^3 of volume or 0.14 displacement tons, masses 2 metric tonnes, provides 0.12 MW of power, requires 0.05 m^2 of a spacecraft's hull surface, costs MCr2, and consumes 3 metric tonnes/hr./tonne of thrust of hydrocarbon distillates that requires 3m^3 of or 0.21 displacement ton fuel with a mass of 3 metric tonnes and costs Cr750.

Are my numbers right for the TL-5 Turbojet?

 

[elbmc1969]

To be really technical, surface area is 0.6, but that only applies on spacecraft.

For an aircraft, at least, that number would be off by quite a bit. The Jumo004 on the Me262 put out less that 1 ton of thrust, but the intake diameter was around 20" and that doesn't count the exhaust. (The intake alone is 0.25 m².) If intake area increases linearly with thrust, and if the exhaust area is half that of the intake (close enough for government work, then the total are needed would be 1.125 m².

Anyhow, that doesn't affect your calculations, which seem to be correct.

 

[snrdg082102]

Evening elbmc,

To be really technical, surface area is 0.6, but that only applies on spacecraft.

I could have sworn I typed spacecraft along with surface area.

For an aircraft, at least, that number would be off by quite a bit. The Jumo004 on the Me262 put out less that 1 ton of thrust, but the intake diameter was around 20" and that doesn't count the exhaust. (The intake alone is 0.25 m².) If intake area increases linearly with thrust, and if the exhaust area is half that of the intake (close enough for government work, then the total are needed would be 1.125 m².

You are correct about the variety of aircraft engines in the real world that exceed the thrust criteria presented in TNE and T4 FF&S. I'm just happy Traveller has aircraft engines at any level.

Anyhow, that doesn't affect your calculations, which seem to be correct.

Thank you for checking my calculations and indicating I'm on the right track.

According to the rules thrust determines fuel consumption and that adding an afterburner increases thrust 1.5 times and doubles fuel consumption.

The turbojet example I used has 6 tons of thrust and consumes 3 m^3 of fuel. Adding an afterburner increase the thrust from 6 to 9. Unfortunately, I've made myself unsure of how to double the fuel consumption rate. Initially, I doubled the 3m^3 of fuel and then I changed to using the afterburner thrust of 9 which changes the fuel consumption to 9.

I am thinking that I should be using the fuel consumption rate for the engine without the afterburner, but now I'm not sure.

I really need some help here.

 

[aramis]

Afterburner doubles the base fuel rate for the engine.

 

[snrdg082102]

Hello aramis,

Thank you aramis for the reply and clarification

Afterburner doubles the base fuel rate for the engine.

To ensure I'm onboard a TL-5 Turbojet with a maximum thrust rating of 6 consumes 3 metric tonnes/hr./tonne of thrust. Lighting off the afterburner kicks the fuel consumption from 3 to 6 metric tonnes/hr./tonne of thrust and puts out 9 tonnes of thrust.

Have I got the method down correctly?

 

[aramis]

Hello aramis,

Thank you aramis for the reply and clarification



To ensure I'm onboard a TL-5 Turbojet with a maximum thrust rating of 6 consumes 3 metric tonnes/hr./tonne of thrust. Lighting off the afterburner kicks the fuel consumption from 3 to 6 metric tonnes/hr./tonne of thrust and puts out 9 tonnes of thrust.

Have I got the method down correctly?

Yes. (mind you, I'm using FF&S2 to verify, as my FF&S1 is 1600 miles away)

 

[snrdg082102]

Evening aramis,

Yes. (mind you, I'm using FF&S2 to verify, as my FF&S1 is 1600 miles away)

Thank you for verifying that I've got how an afterburner changes thrust and fuel consumption. One more item that I've got working correctly in my spreadsheet.

I have at my fingertips TNE FF&S, TNE FF&S Mk I Mod 0, and T4 Book B FF&S, aka FF&S2. When I started looking at T4 QSDS 1.5e and SSDS file by David Golden my first impulse was to check T4 Book B FF&S. When I figured out that the two design sequences didn't line-up with the T4 FF&S I began comparing TNE FF&S/BL with T4 QSDS 1.5e, SSDS by David Golden and T4 FF&S.

There is a lot of common ground between TNE FF&S and T4 FF&S. The equation T4 Thrust = Accel x Volume x 10kN works the same as in TNE, provided I remember that in T4 Volume is in displacement tons.

 

[snrdg082102]

Morning all,

I Have discovered that my TL-5 Turbojet price is a bit off since somewhere along the line I deleted the look-up for the MCr modifier.

A TL-5 Turbojet with an output of 6 tonnes of thrust requires 2 m^3 of volume or 0.14 displacement tons, masses 2 metric tonnes, provides 0.12 MW of power, requires 0.05 m^2 of a spacecraft's hull surface, costs MCr2, and consumes 3 metric tonnes/hr./tonne of thrust of hydrocarbon distillates that requires 3m^3 of or 0.21 displacement ton fuel with a mass of 3 metric tonnes and costs Cr750.

Are my numbers right for the TL-5 Turbojet?

Per TNE FF&S p. 70 a TL-5 turbojet has an MCr multiplier of 0.15 per cubic meter of thruster: MCr0.15 x 2m^3 = MCr0.30.

I caught the error when I was working on the liquid fuel rockets.