I have been working with spreadsheets to estimate the mass and performance of spacecraft in the Sublight Universe. But over time, those spreadsheets have become increasingly hard to maintain. Also, being Microsoft Excel, strange things happen when I'm not looking at them.

After having yet another starship go pumpkin, I have decided to formalize my starship performance estimator into an easy-to-use browser application.

Rocket equations are pretty complicated. So before we start fiddling with exponets and running non-linear equations backwards, we should nail down all of the details that we don't intend to change. Ships are build for a purpose, and that purpose takes precedence over every other consideration.

Example Frigate

Gross statistics for the vessel

project_name A name for this project   tons
vehicle_wet_mass Total Mass of vehicle at launch (m0)
vehicle_dry_mass Total Mass of vehicle (minus propellent) at launch (mf)
vehicle_propellent_mass Mass of all propellent expended
vehicle_mass_empty Mass of Vehicle without propellent, fuel, cargo, or stores
vehicle_volume Total enclosed volume
vehicle_compliment Souls on board

Vehicle Design

Mission Calculation Details

If this is a science or reconnaissance mission, what sort of equipment are you dragging along, and how long will you be observing/patrolling/spying? Does you ship carry cargo?

When estimating tonnage, here are some figures:

Mass (kg) Mass (mt)
metric tons
Reference object
16000 16 a greyhound bus
36000 36 a fully loaded semi-truck
80000 80 a fully loaded Boeing 737-800
450000 450 a fully loaded Boeing 747-8
2.8e+06 2800 a saturn V rocket
3.8e+06 3800 Perry Class frigate
8.6e+06 8600 Arleigh Burke destroyer
5e+07 50000 a cruise ship
1e+08 100000 Nimitz Class carrier
3.5e+08 350000 the Empire State Building
8e+08 800000 the Pentagon
6.4e+09 6400000 Hoover Dam
6.7e+15 6700000000000.0 Asteroid 433 Eros
1.21e+16 12100000000000 Lake Superior (the water at least)
Mass (kg) Mass (mt)
metric tons
Reference object
10000 10 X-Wing Fighter Star Wars
710000 710 Danube Class Runabout Star Trek
1.2e+06 1200 Millenium Falcon (est) Star Wars
5e+07 50000 CR90 Corvette (Tantive IV) Star Wars
7.5e+07 75000 B'rel Class Bird of Prey Star Trek
7e+08 700000 Uss Voyager NCC-74656 Star Trek
3.2e+09 3200000 Uss Enterprise NCC-1701-E Star Trek
4.5e+10 45000000 Imperial Star Destroyer (est) Star Wars
8.5e+10 85000000 Van Gogh Class (Full Load) Sublight
9.1e+12 9100000000 Babylon 5 Babylon 5
mission_equipment_mass Mission Equipment Mass kg
mission_equipment_volume Mission Equipment Volume m3
mission_manned_volume Volume of manned spaces devoted to mission (if not included in habitat)   m3
mission_equipment_rho Density of Mission Gear kg/m3
mission_equipment_constant_power How much power does this equipment draw for the entire voyage   kwh/day
mission_equipment_mission_power How much power does this equipment draw while the vessel is in the mission stage   kwh/day
mission_mass_cargo Max cargo capacity kg
mission_volume_cargo Cargo Volume m3
mission_cargo_rho Expected Density of Cargo kg/m3
mission_cargo_constant_power Power required to maintain cargo   kwh/day

How many people are going to be along for the voyage?

Crew Calculation Details
souls_aboard Number of souls aboard   people
rotational_radius Outer radius of rotational habitat   m
rotational_gravity Force of rotational gravity for non-thrusting phases   G
survival_endurance Number of days the crew are sustained in case of loss of main power   days
waste_endurance Number of days worth of waste that can be stored between engine firings   days
vehicle_endurace Total Mission Length   days
habitat_volume_per_capita Volume per soul aboard   m3
habitat_furnishings_estimate Mass of furnishings and equipment per unit volume of inhabited space   kg/m3
waste_water_recycle_factor Percentage of waste water that is recycled   0.0-1.0
eject_trash Trash and sewage are ejected prior to each thrust stage  
incinerate_trash Trash and sewage are burned in the engines  
potable_propellent Crew potable water can be drawn from propellent tanks  
total_accommodation_volume Total volume enclosed by the accommodation
total_accommodation_mass Total volume enclosed by the accommodation
accommodation_mass_potable_water Total mass of potable water in storage tanks
accommodation_provision_mass Total mass of food and other consumables
accommodation_solid_waste_per_day Total mass of solid waste (trash) generated from food wrappers and other consumables per day
accommodation_water_waste_per_day Total mass of sewage and waste water generated by the crew per day
accommodation_power_daily_kwh Power usage of habitat

Here is where we spec out the reactor and engines to use

Reactor Calculation Details

Putting in the reactor, engines, and other fun stuff

We are playing a guessing game with physics. The heavier our space craft is, the more engine we will need to get it up to the speed we want it to go. But the curves on those equations are not-exactly easy to estimate. So we start with a guess, solve the equation, and then keep refining our guess until the calculated mass of the ship matches our hunch.

structural_density Estimate of structural mass per unit volume required. (Steel ship construction: 173 kg/m3)   kg/m3
vehicle_dry_mass_estimate Design estimate of the mass of the vehicle, minus propellent   kg
design_accelleration Accelleration engines would impart on empty ship (9.8 = 1G)   m/s2
design_thrust Design Thrust of the vessel
power_reactor_wall_density Density of the material. (Default: Titanium)   kg/m3
power_reactor_wall_thickness Thickness of reactor wall. (Default: Titanium)   m
power_reactor_wall_youngs_modulus Tensile strength of reactor wall. (Default: Titanium)   Pa
power_reactor_wall_yield_stress Tensile strength of reactor wall. (Default: Titanium)   Pa
power_reactor_wall_safety_factor Safety factor for reactor wall  
power_storage Auxiliary power stored in flywheels   kwh
velocity_exhaust Effective exhaust velocity of propulsion technology   m/s
propellent_efficiency Efficiency of converting reactor power to propellent kinetic energy   kg/s
reactor_efficiency Efficiency of converting nuclear power to reactor power   kg/s
engine_count Number of engines
3 needed for proper thrust vectoring, more add survivability
propellent_flow_rate Rate of propellent expended (mdot)

Voyage Design

Quick guide to rocket science
departure_distance Distance of mission   au
departure_deltav DeltaV for the first leg of the trip m/s
cargo_departure_mass Cargo Mass   kg
departure_booster_deltav DeltaV imparted by a launch vehicle or booster for first stage   m/s
return_distance Distance of return mission (0=one way trip)   au
return_deltav DeltaV for the second leg of the trip m/s
cargo_return_mass Collect Mass - Materials collected from remote site   kg
mission_loiter_days Number of days vessel will loiter in mission area   days
mission_loiter_deltav DeltaV Reserved for Mission   m/s