# Internet of Spacecraft for Multi-Planetary Defense and Prosperity
## 2 Extra-Terrestrialization: Make Life Multi-Planetary
### Space Transportation  
It has not been long since humankind learned how to combat gravity, and transportation between the Earth's ground and outer space is still expensive and challenging. The space industry has been conventionally a capital-intensive risky business [28]. The launch cost of the earliest launch vehicles such as the Vanguard rocket was $894,700 US dollars (USD) per kilogram when using the consumer price index (CPI) calculator to correct the cost to the reported date (in 2018) [29]. The figure below summarizes and illustrates more historical data [29, 30] of launch costs dating back to 1957, with the CPI calculator used to correct the original data (in 2018) to the end of 2021.  
As shown in Figure 5, the orange round dots indicate the launch costs to the LEO in USD per kilogram (USD/kg). The maximum and minimum costs are almost 1000 times separated due to technological advancements and productivity improvement. Another critical factor accelerating this disruption is the aforementioned private capital invested in the space industry in recent years. Since its first commercial mission in 2013, SpaceX has led the commercial launch service. One critical milestone was marked in 2015 when SpaceXsuccessfully launched and related its Falcon 9 rocket on the ground pad [8], which paved the road for the launch vehicles' reusability and even lower launch cost.  
A trend line based on existing available data indicates the general tendency of the cost change over a 60-year time period, which is a bit distant above the green triangular representing NASA's goal to bring the cost down to USD 100/pound or USD 220/kg in 2025 [31]. However, the scheduled first orbital flight of SpaceX's Starship that can deliver more than 100 tons (150 tons [26]) of payload to the LEO [32], might bend the trend line significantly downward in 2022. According to [PERSON], the CEO and principal designer, the launch cost is estimated to be USD 2 million per launch [33], which can significantly reduce the cost to USD 20/kg.  
However, the listed costs in the table are only for the launch reaching the LEO, while the trip to the Moon and Mars will cost significantly more. Take Falcon 9 for example, the mass of payload to LEO is 22.8 t and will be reduced to 8.3 t and 4 t for reaching a geosynchronous transfer orbit (GTO) and a Mars transfer orbit (MTO), respectively. Correspondingly, the cost of GTO and MTO will be 2.75 and 5.7 times higher than LEO. The reusability, large capacity, and advanced massive fabrication of launch vehicles could significantly lower the cost.  
A payload comparison is summarized in [33], and it is worth mentioning that Big Falcon Rocket (BFR) was renamed after November 2018 by SpaceX, and the two-stage vehicle is technically composed of two parts, Starship (spacecraft) and the Super Heavy rocket (booster). As observed from the comparison in Figure 6, the Starship (with booster) is the most capable launch vehicle in human history and even outperforms SATURN V by >7%. All well-known rockets are presented and compared in height and payload.  
Figure 5: Low earth orbit launch cost change over time with 2021 CPI weighted.