On July 20, 1969, Neil Armstrong made history by taking the first steps on the moon. His “one small step” took decades of research, planning, and innovation from more than 400,000 engineers, scientists, and other technical professionals who were involved in the historic moon mission. Now, 50 years later, this research stands as the foundation for new missions and more ambitious space exploration–back to the Moon and beyond.
To recognize the anniversary of the Apollo 11 mission, we’ve highlighted some of the key IEEE research that was critical in advancing the science that took us to the moon five decades ago, as well as recently published research that may form the basis of space missions for decades to come.
Navigating in Space
For vehicles to navigate in space, two-way radiometric measurement is often used, where range and Doppler are measured by the time taken for a radio signal to travel to and from the transmitting station and spacecraft. In 1965, researchers from the Radio Corporation of America proposed a design for the radar transmitter units for the Lunar Excursion Module (LEM). In the original paper, found in the IEEE Xplore digital library, the researchers detail the practical requirements of this unit, including its ability to resist shock and vibration, its freedom from microphonic interference, and the minimization of electromagnetic radiation—all factors that are still used to evaluate transmitters today.
Figure 1 (below) is a composite diagram of the frequency multiplier, which shows how the unit was able to increase the power and range of transmission so that its signal could be received on earth.
Figure 1: Composite Diagram and Photograph of LEM Frequency Multiplier
Since this research was published, we’ve travelled much further into our galaxy, and beyond, and come across new navigation challenges to overcome. As a spacecraft travels further from Earth, the lag time of a two-way navigation system grows and is not competent enough to perform navigation tasks when astronauts need real-time position information to safely navigate to destinations.
To tackle this problem, research funded by the National Science Foundation of China has formulated a solution to collect and process one-way radiometric signals from a single transmitting station onboard a spacecraft to enable autonomous real-time navigation. Using the Deep Space Atomic Clock (DSAC), launched on June 25, 2019, the spacecraft does not have to retransmit signals to the Earth station to obtain two-way measurements. The DSAC, developed at NASA’s Jet Propulsion Laboratory, is a mercury-ion atomic clock about the size of a toaster and is 50 times more stable than existing space clocks. By combining the signal with inertial tracking data collected onboard the spacecraft, accurate autonomous navigation in deep space can be achieved.
Future of Space Communications
One of the challenges the space navigation researchers faced was the Earth’s rotation breaking the uplink signal to the spacecraft. To fix this issue, they suggest three transmitting stations be set around the globe to ensure a continuous uplink.
NASA, however, is already working on a different solution to this problem. With a Next Generation Relay (NGR) system in the geostationary orbit of Earth, the need for space stations outside of the US will be eradicated. The NGR system, set for launch in 2025, will consist of two spacecraft nodes, one acting as the ‘hub’ and the other, the ‘spoke’. Lunar ‘users’ will interact with the ‘spoke’, and a 100GBps laser crosslink will transfer the data to the ‘hub’, and then to Earth, as seen in Figure 2 below.
Figure 2: NASA’s planned Next Generation Relay constellation in GEO in 2025.
This “hub” and “spoke” technology dates as far back as 1966 and was originally used to channel communications from the Lunar Excursion Module (LEM). Developed by the Radio Corporation of America, this methodology helped shape the development of NASA’s new relay system. Instead of lasers, the original Moon landing research outlined a system that relied on the setup of a physical antenna on the Moon. This antenna enabled the transfer of television imagery and S-Band electromagnetic radar signals to transmit voice signals to the command base and back. Figure 3 illustrates how this equipment was designed and functioned in space.
Figure 3: LEM in-Flight and Moon Surface Communications
Advances in Spacecraft
In order to travel to the Moon and back, research published in IRE Transactions on Space Electronics and Telemetry in 1959 established the vehicle and fuel requirements for the expedition. These important findings became the foundation for the LEM launched ten years later. The vehicle (detailed in Figure 4 below) was calculated to be 220 feet tall and consisted of six engines, each with 1.5 million pounds of thrust. The ship was split into five stages, as broken down in Table I, each stage playing a different role in the journey.
Figure 4: Outline drawing of the proposed manned spacecraft and its weight breakdown
Now, in 2019, NASA is referencing those same requirements to send a team to Mars and back — a journey that’s over 500 times as far as the Moon. In order to accomplish this, new research points to the use of autonomous robots that will be deployed on Mars’ surface to mine for water, oxygen, and rocket fuel. These robots will ensure the team will have enough supplies to live on the planet and enough fuel to make the long journey home. The plan is to have these autonomous robots continuously mine Mars so that when the next expedition arrives, they are prepared with water, oxygen and fuel.
Figure 5: Martian Robotic Factory
Looking to the Moon and Beyond
In the 50 years that have passed since the Moon landing, space technology has made leaps and bounds, turning what was an ambitious objective in 1969 into a small stepping stone for the exploration of our galaxy. Since that first step, researchers have created new technologies to take us much further into space, and our ambitions have grown to now look at travelling to Mars and setting up a manned space-station on the Moon.
Recently, the United States government committed to an acceleration of these plans and aims to set foot on the moon once again in 2024. Much like the 1969 Moon landing, what we now consider ambitious may seem minute in 50 years’ time, and the ground-breaking research that’s being published with IEEE today, could become the foundation for unimaginable space expeditions in the future.
For more information on space technology, visit the IEEE Xplore digital library.