A few weeks ago I mentioned that I was working on fixing the Hard Times
and One Small Step engine design tables. I've completed the hard
part of this. It's not all done, but the game-design parts are.
Notably missing are costs and power in and out and several items
such as Ion engines I haven't had a chance to evaluate completely
yet. (Ion and MPD in particular may be a bitch to handle properly
for reasons that would take an article of itself to explain).
What's here is usable to design things. Go forth and enjoy 8-)
Without further ado, the table:
Revised Hard Times Table 5.1 LOW TECH THRUST BASED PROPULSION
TL Type TT Mass Vol Fuel F_Typ P_Req. P_Out. MCr
3 Solid 20 1.0 1.0 - Solid - - ?
4 Resistojet 0.005 1.0 1.0 1.0 Water 0.1 -
4 Solid 30 1.0 1.0 - Solid - -
5 Hyp Liquid 30 1.0 2.0 720 Hyp Liq
5 Liquid 35 1.0 2.0 545 Liquid
5 Solid 35 1.0 1.0 - -
6 Hyp Liquid 35 1.0 2.0 700 Hyp Liq
6 Liquid 40 1.0 2.0 605 Liquid
6 Solid 40 1.0 1.0 - -
7 Hyp Liquid 40 1.0 1.5 685 Hyp Liq
7 Liquid 45 1.0 1.5 570 Liquid
7 LH Liquid 40 1.0 2.0 1050 LH Liq
7 Solid 45 1.0 1.0 - -
7 Hybrid 40 1.0 1.0 515 Liquid*
7 Ion
7 Mass Driver
7 NTR 5 10.0 4.0 350 LH
8 LH Liquid 50 1.0 2.0 1200 LH Liq
8 MPD
8 NTR 10 10.0 4.0 570 LH
8 Xptl F Rkt. 150 10.0 1.0 150 LH
8 Mass Driver
9 Fusion Rkt. 200 4.0 1.0 205 LH
Fuel Types:
Type Weight Cost (Cr/KL) Comments
Water 1.0 negl. Usually free
Solid - Cr50,000 Really the engine, not the fuel
Hyp. Liquid 0.75 Cr150 Baseline: Hydrazine + Nitrogen Tetroxide
Liquid 0.95 Cr50 Kerosene / LOX
LH Liquid 0.35 Cr70 Liquid Hydrogen / LOX
Ionizates 1.5 Cr100 Liquid Xenon etc.
Liquid Hyd. 0.07 Cr?? Per Ref Manual
Rock 1.0 negl. for Mass Driver
Abbreviations and Acronyms, and more info:
Hyp : Hypergolic, where two fuels burn on contact with one another.
Hypergolic fuels are extremely toxic
LH : Liquid Hydrogen
Liquid : Liquid Oxygen & Kerosene (baseline)
Hybrid : LOX / Solid Fuel rocket. * while fuel is actually solid rubber or
similar material, the fuel for Hybrids should be treated as Liquid
as it has nearly identical characteristics
NTR : Nuclear Thermal Rocket. Can be designed to run on another fuel
such as Water. In this case, the volume of fuel used is the same
but the thrust increases to x8 base thrust.
Reviser's Notes:
I've broken liquid fuel engines into three categories: "normal" liquid
fuel engines, running on some hydrocarbon (usually kerosene or a rough
equivalent) and Liquid Oxygen (LOX), "hypergolic" liquid fuel engines,
running on something like Nitrogen Tetroxide and Hydrazine, and "Liquid
Hydrogen" rockets, runnong on LOX and Liquid Hydrogen.
Each has its own advantages and disadvantages. Normal liquids are reliable
and cheap and low-tech. Liquid Hydrogen improves performance at the cost
of reliability, something which I'm striving to write some rules for.
Hypergolics are the most reliable (and cheapest, engine wise), but the
fuels are excessively toxic and hard to handle (remember that Titan silo
that blew up around 1985 ?).
I've added Hybrids, where a liquid oxidizer and a solid fuel are burned in
a thrust chamber sort of like a solid rocket engine. These need more
work, and I'm doing it, but right now a real-world hybrid engine rocket
design of mine is eating my time and such 8-) so don't expect it soon.
All of the listed values correspond with known specific impulse, barring
mathematical error while I was calculating them (I spot checked a few and
they're right, so they in general are pretty close).
Enjoy. 8-)
- -george william herbert
[email removed] [email removed]