# Internet of Spacecraft for Multi-Planetary Defense and Prosperity
## 1 Introduction  
Since the first artificial Earth satellite, Sputnik 1, was sent into an elliptical low Earth orbit (LEO) by the Soviet Union (USSR) on 4 October 1957, humans have opened a gate to the space age. Another historical milestone was carved by the National Aeronautics and Space Administration's (NASA) Apollo 11, the first crewed spacecraft to land humans on another celestial body, the Moon, on 20 July 1969 at 20:17 coordinated universal time (UTC). To date, tens of thousands of spacecraft have been sent to outer space which is defined by the von Karman line at 100 km above Earth's mean sea level. By the generalized definition, a spacecraft is a vehicle or machine designed to fly in outer space, and it can be categorized into two major types: crewed and uncrewed. As of 2021, only three nations have flown crewed spacecraft, the USSR/Russia, the USA, and China. The first crewed spacecraft, Vostok 1, was made by the Soviet Union and carried Soviet cosmonaut [PERSON] into space in 1961, while the second crewed spacecraft named Freedom 7 was launched by United States, also in 1961, and carried the first American astronaut [PERSON], to an altitude of just over 187 km (km). On the other hand, uncrewed spacecraft include Earth-orbit satellites, lunar probes, planetary probes, asteroid/comet probes, and other deep-space probes. More details about examples of both crewed and uncrewed spacecraft launched are presented in Table 1.  
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For the crewed spacecraft, governments played a key role initially. The Apollo 11 mission made a critical historic accomplishment of landing mankind for the first time on another celestial body in 1969. The first and biggest space station that has been collaboratively built and operated by several countries, the International Space Station (ISS), has been in service since 1998 and has been visited by 244 persons from 19 nations. The lunar module of Apollo 11 mission and the ISS are illustrated in Figure 1 (This file is in the public domain in the United States because it was solely created by NASA. NASA copyright policy states that \"NASA material is not protected by copyright unless noted\". NASA copyright policy also applies to some other images used in this paper). However, a noticeable trend in recent years is that the commercial space industry fueled by private capital has exponentially grown to accelerate technological transformation. One of the most influential corporations is Space Exploration Technologies Corp. (SpaceX) headquartered in Hawthorne, California. In 2015, SpaceX successfully launched and related a Falcon 9 rocket [8] and launched a returned Falcon 9 later in 2017, which paved a promising road to low-cost reusable launching vehicles. Moreover, SpaceX's Falcon 9 booster that launched the Crew-1 mission with the Crew Dragon Resilience in November 2020 is being reused for the Crew-2 mission, which is the first time the same rocket booster has been used for multiple human launches. The SpaceX Crew Dragon and Starship spacecraft are illustrated in Figure 2. Other non-governmental aerospace companies include California-based Virgin Galactic, which develops commercial spacecraft and provides suborbital spaceflights to space tourists, and Kent (Washington) headquartered Blue Origin, which also develops reusable launching vehicles and orbital technology.