Specs from the Browncoats:

The Serenity is a Firefly Class interplanetary ship. Originally conceived and built as a medium range cargo ship.

Dimensions and Weights:

She is comparable to that of Boeing 747. She is 63 meters long, 40
meters wide and 18 meters tall. Her gross empty weight is 575,000 lbs
and her maximum takeoff weight is 945,000 lbs.

Performance and Powerplants:

Primarily powered by 2 wing mounted Smith Davis SD-2595 (95,000
lb) turbofan and solar induction engines, she can achieve a maximum
airspeed of mach 2 (1484 mph) at 1000 Meters EBSL (Earth Based Sea
Level,) and mach 30 (22270 mph) at 100,000 Meters (62 miles) EBSL.
During the transitional phase from atmospheric to orbital flight the
fan blades rotate to collect photons emitted by a solar source to feed
the engines keeping the relative thrust ratio comparable to it’s
atmospheric rating.

The Firefly engine, a Smith Davis SD-4631 photon reaction drive,
was developed on the same principles that drive fusion in a star, (4 1H
+ 2 e — 4He + 2 neutrinos + 6 photons.) The reaction produces
enough thrust to propel the ship to 643,738 kph (400,000 mph) taking it
approximately 16 days to travel 1 AU. (The Astronomical Unit is the
distance from the Earth to the Sun, 149,597,871 kilometers.) Although
very reliable, this reaction produces large volumes of plasma as hot as
the surface of a star. Thermal panels on the outside of the engine
dissipate the plasma and heat that builds up during the process
typically glowing in a yellowish hue as they cool down.


The maneuvering of the ship is handled in two different ways. In
atmosphere she has flaps and ailerons that in conjunction with the
pitch of the side engines control her direction. In space she uses an
RCS, (Reaction Control System,) consisting of Hydrazine fueled
thrusters that work in a countered measure. For example if she were to
turn nose up, thrusters on the back rear of the ship would fire upwards
and thrusters of the front nose would fire downwards pushing the tail
down and the nose up. Variations on this, tied into the side engines
pitch, produce all her movement in space.

For landing her side engines rotate vertical and vents on the front of
the engine open to allow the engine the breathe as she hovers.


The Firefly class ships gravity comes from a rotating ring just aft of
the ships midsection. It produces a gravity field using the “Peristere
Principal,” that also acts as an momentum dampener to allow passengers
more freedom of movement during all aspects of flight.