[DaltonS]

Originally Posted by DaltonS

Here is an enlarged version of the Perdue-class Semi-Cycler.
Please note that:

1. While this ship contains no superscience systems, it is listed as TL9^ because the Orbital Taxis it uses have a reconfigurable fission reactor/NTR ram-rocket to power its VASMIR drive and liftoff from Mars. (I'll post its design later.)
2. The control room remains the same size (SM+8 system) and the crew habitats have been moved from the center and rear hulls to the front hull core.
3. While the semi-cycler still launches in a 2-year free return trajectory for safety reasons, its doubled ∆V allows it to perform the Mars Orbit burn itself, so it can loiter in Mars orbit until the proper return window occurs.

Wow! I didn't mean to post the Orbital Taxi design this much later, but a promise is a promise.

MARS TRANS-ORBITAL TAXI
PILOTING/TL9 (LOW-PERFORMANCE SPACECRAFT) or PILOTING/TL9 (AEROSPACE) Page:

TL            Name           dST/dHP  Hnd/SR  HT       Move       LWt.     Load    SM      Occ      dDR   Range   Cost   
9^  Mars Trans-Orbital Taxi     50     -4/5   12  0.0002G/10 mps   300  167.3 [2]  +7  3+20SV [3]  7/5/5    —    $11.8M

Length: 60 yd. (180 ft.) Crush Depth: 6.3 Atmospheres (208 ft.)
Power Points: +1 / -1
Space Performance #1: Hnd/SR: -4/5 sAccel: 0.0002Gs/10 mps
Space Performance #2: Hnd/SR: -4/5 sAccel: 0.002Gs/0.5 mps
Space Performance #3: Hnd/SR: -1/5 sAccel: 1.4Gs/2.025 mps
Air Performance: Hnd/SR: +3/6 aAccel: 1.4Gs (30.8 mph/s) aSpeed: 3,000 mph (1,500 yps / 0.83 mps)

SHIP SYSTEMS

   FRONT     
[1]          Advanced Metallic Laminate Armor
               dDR 7
[2]          Control Room
               Comp: C5 / Comm/Sensor: 5 / 3 Stations
[3]          Passenger Seating
               20 Seats
[4-6]        Cargo Hold
               45 Tons / SM+3 Bay Doors

   CENTER    
[1]          Metallic Laminate Armor
               dDR 5
[2-6, Core]  Cargo Hold
               90 Tons / SM+3 Bay Doors [6]

    REAR     
[1]          Metallic Laminate Armor
               dDR 5
[2!]         VASIMR Electric Rocket
               0.0002 Gs / 10 mps / 0.002 Gs / 0.5 mps / 95 days Fuel [5,5,8]
[3]          Reconfigurable System
  [a†]       Fission Reactor
               1 Power Point / 50 yr Fuel [7]
  [b]        Nuclear Thermal Rocket
               1.4 Gs / 2.025 mps / 2.83 min Fuel [4,5,9]
[4]          Fuel Tank
               15 Tons of Methane
[5-6]        Cargo Hold
               30 Tons / SM+2 Bay Doors [6]
[Core]       Fuel Tank
               15 Tons of Hydrogen

Design Switches, Features, & Notes: 3 Airlocks (Capacity: 3 people each), Fuel Cost: $97,500; Total Cost: $11,897,500
IR SIGNATURE: +12 (+6 Fission Reactor, +6 Nuclear Thermal Rocket)
CAMPAIGN OPTIONS: Exposed Radiators [1], EBS's Unofficial rules
SHIP OPTIONS: Streamlined, Winged
[1] Counts as Exposed System when deployed (see p. SS1:66), Targeted at SM+7 if central hull is facing attackers, SM+2 otherwise
[2] Load includes: 2.3 tons of Crew & Passengers, 165 tons in Cargo Hold
[3] Crew Requirement: 3 Control Stations (1 Pilot/Sensor Operator, 1 Co-Pilot/Navigator, 1 Payload Specialist)
PERFORMANCE PROFILES: [4] Air #1, [5] Space #1
[6] Collapsible Methane Tank
FUEL USED: [7] Fissionables, [8] Hydrogen (15 tons), [9] Methane (135 tons)
TROOP STRENGTH (TS): 0 CLASSES: Air, Space FEATURES: Night, Sealed

Created using the GURPS Spaceships Design Spreadsheet Version 2.0 RC 29 copyright © 2009-2017 Eric B. Smith. This spreadsheet is based on information contained in the GURPS Spaceships series of books.

This is my first Mars Trans-Orbital Taxi which had two hard tanks (LH2 and CH4) for VASMIR and NTR(RR) drives, and 8 collapsible methane tanks in the middle and rear cargo holds for Mars launch. My rationale was the Earth/Mars trade imbalance during the early years: 165 tons imports vs. 45 tons exports. (Also, reducing the ship's effective mass by 45% on takeoff extends the LH2 tank's ΔV by 81%. ;) ) After achieving maximum airspeed of the ram-rocket (0.83mps) the rocket mode of the NTR can reach Martian orbital velocity (2.48mps) with 0.35mps ΔV to spare. It will then change to reactor mode, powering the VASMIR drive to rendezvous with the semi-cycler. Even with 5.68mps of the VASMIR's ΔV used by that point, the remaining 4.32mps will extended by Taxi's lowered mass to 7.8192mps leaving 2.1392mps ΔV to spare.

While this model of Taxi would work well with the larger version of the Perdue that made the one-tangent burn itself and was orbiting Mars, it should have been originally conceived as a long range craft. I finally calculated how long the burn would take at 0.0002 Gs (a bit less than 54 days) and boy, was I embarrassed! My first mod involved making the Passenger Seating system modular and that just added $100k to the cost. I'm sure the bean counters would have insisted on making it permanent when the larger Perdue went into service to save money (well that's the excuse I'm using anyway). Next I replaced that system with a habitat module for the crew with 1 bunk room, 3 hibernation chambers and 1.25 tons of steerage cargo, 0.45 tons of which would be food. (This allows a supercargo to use the left over bunk without bringing their own rations.) This adds $500k to the original cost.

Dalton “just call me an equine necromancer … again!” Spence