Hello all,
after following the discussion on TML and after a weekend of working on designs,
here is my opinion to the problem (and three designes at the end):
At first I suggest a seperation in designs of Spaceships - vehicles which
do not touch an atmosphere - and Orbiter - which are designed to bring payload
to orbit. I think Orbiter should be designed using COACC rules, Spaceships
using Hard Times + Craft Design from the referee's manual.
But no matter using the COACC rules for an Orbiter results in a couple of
problems. To show the different problems, I will suggest designs, and show
the problems they include.
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To build a cheap Orbital Transfer Vehicle the government of ....(please
insert world) a TL 7 world chooses to design a two stage vehicle. The first
stage should use air breathing engines to reach to the extreme point of
the atmosphere. There the second stage will be launched and engage its engines
to reach a low orbit or a "will be" low orbit space station. The second
stage is intended to carry 8 tons to orbit.
The calculation leads to 65 minutes to reach the extreme point of the
atmosphere using High Performance Turbofans and a thrust resulting in 2.73 g
acceleration. The upper stage is intended to use High Performance rockets at
3.9g acceleration for about 30 seconds. (Please remember High bypass Turbofans
are not available on TL 7.)
The result of this calculation, the following two designs are launched:
CraftID: Sanger - Supersonic lower stage, TL 7, Cr=28,128,720
Hull: 1600/4000, Disp=1780, Config=1AF(Supersonic),
Weight loaded=400tons, Armor=none
Power: 18 MW (drawn from engines), Endurance=99min
Locomotion: 4/10 High Performance Turbofans x 4, Thrust=1092 tons,
Top=2800, Cruise=2100, Min=280, Agility=9
Communication: Radio=Planetary x 2
Sensors: Radar=regional (all weather)
Off/Def: -
Control: Computer=0bisx3, Computer enhanced Fly-by-Wire, 6 MP,
Environment=basicEnv,basicLS
Accom: Crew=4 (Pilot, Copilot, Engineer, Launch Operator),
Complex Cockpit x 4, advanced ejection seats x 4
Other: Fuel=164,000 liters (164 kl for an endurance of 99 minutes),
Cargo=Subcraft=Orbiter= 40 tons
Please remember: the disp. of the upper stage orbiter is included in the
disp of this vehicle. So the real disp. is 1602 if you like.
CraftID: Hermann Oberth - Orbit Vehicle, TL 7, Cr=7,031,440
Hull: 160/400, Disp=178, Config=1AF(Hypersonic STOL),
Weight loaded=40tons, Armor=none
Power 1: 3.12 MW (drawn from engines), Endurance=2min
Power 2: FuelCells(x2)=0.18 MW, Endurance=336h (=14 days)
(This power plant supplies life support and electronic
equipment)
Locomotion: 4/10 High Performance Rocket (x4), Thrust=156tons,
Top=3200kph, Cruise=2400kph, Agility=10, min=175 kph
Sensors: Magnetic Sensor, Radiation Sensor
Commo: Radio=Planetary, Regional(x2) (for EVA)
Off/Def: -
Control: Computer=0bis(x3), Computer enhanced Fly-by-Wire, 6 MP,
Environment=basicEnv,basicLS,extLS,AirLock
Accom: Crew=4, (Pilot, Copilot, 2 Mission specialists)
Complex Cockpit x 2, Passenger Section x 4 (some extra
space for life on orbit), Rocket Escape Pod x 4
Other: Fuel=3200 liters (Rocket), Fuel=330 liters (FuelCells),
Cargo=8081.4 liters (=kg), Hvy Robotic Arm
The Cargo Bay can be opened to space to release satellites. The robotic
arm can be used to support launch sequences of satellites or to support
EVA (Extra Vehicular Activities).
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Now the Problems:
I have used Computer enhanced Fly-by-Wire controls for both vehicles. As
a result, these controls needs lot of power. As I know from reality, APUs
(Auxiliar Power Units) supply about 300 KW of electric energies, even a
747-400 needs much less then 1 MW to support the control functions of its
Fly-by-System. I think the energy consumption of the COACC Controls are
to high. What is meant by "Controls" of COACC ?
I need fuel cells for the Orbiter. No other powerplant can be used, to support
the energy needs in an sealed environment. But Fuel Cells are at TL 10 refering
to the referees manual. Any comments ?
After I have finished this two designs, I looked on Hard Times for a second
time. They calculate the time to reach an LPO using the g-ratio (the weight
to thrust ratio) of the vehicle. But to calculate the time, to reach the
edge of the atmosphere using air breathing engines, they calculate 10 times
the time of a rocket launch. As a result, only the last 10% of the way to
the orbit had to be done by rockets. I conclude the following:
90% of a flight to orbit can be done using airbreathing engines.
That's the basic of the following design:
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After calculating the Sanger two stage project, a smart engineer suggests
an alternative:
CraftID: Space Train - One stage Orbital transfer Vehicle, TL 7,
Cr 31,140,520
Hull: 1600/4000, Disp=1780, Config=1AF (Hypersonic STOL)
Weight loaded=400tons, Armor=none
Power 1: 18 MW (drawn from engines), Endurance=500sec
Power 2: Fuel Cell (x30), 2.7MW, Endurance=346h (>14days)
Loco 1: 4/10 High Performance Ramjet (x4), Thrust=1638 tons,
Top=3300kph, Cruise=2475kph, min=175
Loco 2: 4/10 High Performance Rocket (x2), Thrust=819 tons,
Top=2000kph, Cruise=1500kph, min=175
Commo: Radio=FarOrbit(x2),Regional(x4)
Sensors: Radar=regional(all weather), Magnetic Sensor,
Radiation Sensor
Off/Def: -
Control: Computer=1bis x 3, Computer Enhanced Fly-by-Wire, 6MP,
Environment=BasicEnv,BasicLS,ExtLS,AirLock
Accom: Crew=8 (Pilot, Copilot, Engineer, Radio/Computer Operator,
Passengers x 4), Complex Cockpit (x4),
Passenger Section(x4), Rocket Escape Pods (x8)
Others: Fuel 1=28kl (for Rocket, 200 sec Endurance),
Fuel 2=42kl (for Ramjet, 300 sec Endurance),
Fuel 3= 4150 liters(for Fuel Cells, 346 hours endurance)
Cargo= 60 tons (exactly: 59957 kg)
The launch profile is the following:
The vehicle is launched vertically, so a launch site is a must. At first,
the Rockets burn for 30 seconds to kick the vehicle up to 800 kph where
at second the ramjets starts. The ramjet will lift the vehicle to the edge
of the atmosphere in about 250 seconds. There the rockets are restarted
and deliever the final kick of 52 seconds to reach the LPO.
1.Stage: Rocket: 30sec at 2.05g => 5.8% of way to orbit
2.Stage: Ramjet: 248sec at 4.10g => 84.2%
3.Stage: Rocket: 51sec at 2.05g => 10.0%
The Fuel for the rockets is 200% of the requiered, so enough safty potential
is build in. The Fuel Capacity can be lowered to get more Cargospace.
This vehicle is MCr 5 cheaper than the two flight units of the Sanger Project
together. A second advantage is the fact, that this unit will carry 7 times
the payload of Sanger and has much more safty potential.
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I have perverted the LALV rules to design the above vehicle. It is able
to reach an LPO in 330seconds or 5 1/2 minutes. And it can carry far more
payload than the Sanger vehicle above.
One more problem of the Hard Times rule is:
They do not think about the landing of the vehicle. They do not calculate
the Fuel needed for reentrance to atmosphere nor they think of the special
Hull a vehicles needs, which try to land aerodynamical and uses the atmosphere
as cheap brake.
As Rob Dean suggest in one of his last emails, we could include this problems
in the calculation of the Hull weight and price. The calculations above are
made without using this. The price of the 3 designs above are done, strict
using COACC rules. That's because I think Hypersonic designes had to stand
heat similar to an landing shuttle (that's one of the problems of hypersonic
flight).
I'm trying to build a complete Space Program. So I will design a space station
and some spaceships (using my definition, see above). Any suggestions to
the designes of this ships (Ion-cruiser, Lunar lander, Lunar Orbiter...)
are welcome.
That's all for the moment,
Juergen
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Juergen Kirsch
Institut fuer Informatik, Universitaet Bonn
Germany
[email removed]