Table 1.
Fig 1.
Suborbital flights: (a) Commercial aviation, suborbital and orbital altitudes, (b) space tourism market and prediction (data from different sources: Space Tourism Industry Research Report, Grand View Research, Global Mart Insights), (c) major carriers of suborbital tourism: Virgin Galactic (VSS), Blue Origin (NS), and SpaceX (Dragon).
Table 2.
The exhaust velocity of rockets using different rocket fuels [56,59,60].
Fig 2.
Outline of the iterative process to solve the kinetics, thrust, and propellent consumption rate during the flight.
The bottom box refers to the derivation of fuel consumption and CO2 emissions (details in the next section).
Table 3.
Table 4.
Table 5.
TSFCs and mixing ratios for Big-3’s engines and fuels.
Table 6.
CO2 emission factors (CO2 vs. fuel) of different fuels [94–96].
Fig 3.
The framework of estimating fuel consumption and CO2 emissions.
Fig 4.
Propellant and CO2 emissions per trip: (a) CO2 emission distribution of HTPB, (b) mass of spacecraft, fuel, and oxidizer, and (c) CO2 emissions due to combustion and production.
Table 7.
Propellant and fuel consumptions and variations.
Fig 5.
Total spacecraft mass and CO2 emissions during flights: (a) mass variation; and (b) cumulative CO2 emissions.
Fig 6.
CO2 emissions at different altitudes: (a) CO2 emissions for ascending and descending phases at different altitudes; and (b) total CO2 emissions at different altitudes.
Fig 7.
The trend of CO2 emissions per flight for different fuels used in suborbital spacecraft.