An Introduction to Satellites

Estimated Reading Time: 7 minutes

TL;DR

Building on last week’s post about rockets), this week we learn more about satellites. We end the post by commenting briefly on nuclear batteries and on the exotic technology of nuclear pacemakers.

A Very Brief History

While satellites have been theorized for centuries, the first human launched satellite to reach space was Sputnik I (pictured below), launched in 1957 by the Soviet Union. Sputnik triggered the start of the space race between America and the Soviet Union. America dramatically increased its investment in science and technology following the launch of Sputnik and succeeded in rapidly launching its own satellites shortly thereafter.

A replica of Sputnik I, the first satellite launched into space. Sputnik triggered a crisis within the US which dramatically accelerated its investment into science to avoid falling behind the Soviet Union (source).

Following the initial launch of Sputnik I, commercial and scientific uses of satellites have exploded. For example, the Hubble space telescope launched in 1990 (pictured below) is a fundamental scientific tool that can take pictures that no earth based telescope can match.

The Hubble Space Telescope generates images of distant space with greater resolution than is possible for ground based satellites (source).

More recent scientific satellites have trended towards miniaturization, with CubeSats (see image below) of scales about 10 cm on a side able to take sophisticated scientific measurements.

A CubeSat is a miniaturized satellite that is commonly used for space research (source).

Today’s satellites use a number of different orbits (pictured below) commonly referred to as low earth orbits, medium earth orbits, and high earth orbits. Different orbits are useful for different kinds of applications. For example, the CubeSats pictured above are mostly commonly deployed to low earth orbits.

Various earth orbits to scale; cyan represents low earth orbit, yellow represents medium earth orbit, the black dashed line represents geosynchronous orbit, the green dash-dot line the orbit of Global Positioning System (GPS) satellites, and the red dotted line the orbit of the International Space Station (ISS). (Caption and image from source).

The commercial market for satellites has expanded tremendously in recent years including applications in imaging, navigation, weather, telephony and more. A number of commercial launch providers (such as SpaceX) have risen to prominence on the strength of this market in the last few years.

Powering a Satellite

One of the (many) challenges in designing a modern satellite is to provide it with a suitable power source. In our earlier article on solar cells, we learned that some satellites are powered by expensive high-efficiency solar cells. Solar power is sufficient for many satellites, but for deep space satellites, more dedicated power sources such as nuclear batteries are required (see image below).

A radioisotope thermal generator (RTG) used on the Cassini Space Probe uses the heat generated by radioactive decay to produce an electric current. An RTG is a type of nuclear battery (source).

Interestingly, nuclear batteries have historically found uses in other applications, including in pacemakers (see image below)! Nuclear pacemakers apparently produced low radiation doses and were extremely long lived, lasting up to 30 years in some cases (compare with the 5-10 year lifespan of today’s pacemakers). The nuclear pacemaker provides a fascinating example of a technology which has no clear equivalent today.

A “nuclear pacemaker” produced by Medtronic powered by a small piece of plutonium. These pacemakers were produced in the 1970s and could be extremely long lived with one patient reporting the pacemaker as still operational 34 years after insertion (source).

Discussion

Satellite technology has evolved from a niche governmental pursuit into a vast commercial market over the last several decades. In next week’s subscriber post, we will delve more deeply into the commercial launch market for satellites.

Highlights for the Week

• https://www.wsj.com/articles/biden-senators-agree-to-roughly-1-trillion-infrastructure-plan-11624553972: The new bipartisan infrastructure proposal focuses on physical infrastructure such as roads, bridges, airports and broadband.

• https://www.wsj.com/articles/canadian-indigenous-group-finds-hundreds-of-unmarked-graves-near-former-school-11624555718: Hundreds of unmarked childrens’ graves have been found near a Canadian “residential school” which was run from 1890 to 1997. These schools were used to remove indigenous children from their families to suppress their language and culture. Awareness is growing of the tremendous harm perpetuated by these schools against indigenous cultures.

• https://spectrum.ieee.org/tech-talk/aerospace/space-flight/chinas-rocket-debris-problem: The PRC rocket program is trying to solve its debris problem.

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About

Deep Into the Forest is a newsletter by Deep Forest Sciences, Inc. We’re a deep tech R&D company specializing in the use of AI for deep tech development. We do technical consulting and joint development partnerships with deep tech firms. Get in touch with us at partnerships@deepforestsci.com! We’re always welcome to new ideas!

Credits

Author: Bharath Ramsundar, Ph.D.
Editor: Sandya Subramanian