SpaceX: An Overview

SpaceX is a company that designs, manufactures, and launches rockets and spacecraft. Elon Musk founded the company in 2002. His goals are to revolutionize spaceflight, provide commercial access to space, and eventually colonize other planets[1]

The Rise of Elon Musk

The rise of Elon Musk; from Blastar to blast-off!

Elon Musk was born in South Africa on June 28, 1971. Musk developed an interest in computers at an early age, and taught himself how to program them. He was 12 when he sold his first software, a game called Blastar. At age 17, Musk moved to Canada to attend Queen’s University and avoid mandatory service in the South African military. In 1992, he left Canada to study at the University of Pennsylvania. He later graduated with an undergraduate degree in economics and a bachelor’s degree in physics. Musk then headed to Stanford University in California, to pursue a PhD in energy physics, however, he dropped out only 2 days after he started attending. He dropped out to try and take advantage of the internet boom, that was just beginning.

In 1995 Elon Musk founded the Zip2 corporation with his brother, Kimbal Musk. Zip2 provided and licensed online city guide software for newspapers. It was used by companies such as The New York Times, and Chicago Tribune. In 1999, Elon Musk sold Zip2 for 341 million dollars to a division of Compaq Computer Corporation. Using money from the sale, Kimbal and Elon Musk founded X.com, which later became known as PayPal. He sold PayPal to Ebay, in October 2002, for 1.5 billion dollars.

During that same year, Elon Musk also became a US citizen, and founded SpaceX. SpaceX’s original goal was to build spacecraft for commercial use. SpaceX started by launching small rockets, as they were relatively cheap, and easy to build. In 2005 SpaceX was awarded an indefinite contract by the US military, allowing it to purchase up to 100 million dollars worth of rocket launches. In 2008, NASA announced that SpaceX won the NASA Commercial Orbital Transportation Services contract, which would have SpaceX deliver supplies to the International Space Station, and possibly transport crew. The contract was for 1.6 billion dollars worth of deliveries. This made SpaceX the world’s first private contractor to deliver cargo to the ISS.

The Birth of SpaceX

A Falcon Heavy rocket blasting off from a SpaceX launch site.

SpaceX had a rough start, the first three launches were failures. The first launch, a Falcon 1 launch in March 2006, failed minutes into its flight due to a fuel line leak. The second launch, another Falcon 1, was launched in March, 2007, and was lost in space, minutes after taking off. In August 2008, the third launch was also a failure, when the first and second stages failed to separate. The fourth launch was successful. In September 2008, SpaceX’s first Falcon 1 made it into Earth’s orbit.

The Bumpy Road to Reusable Rockets

The bumpy road to reusable rockets

One of SpaceX’s greatest accomplishments is landing and reusing rocket stages. The development of reusable rockets began on September 21, 2012. SpaceX built a prototype around the empty tank of an early version of the Falcon 9 rocket. The US Federal Aviation Administration, that licensed the test, didn’t allow it to go more than half a mile above the ground. The 8 tests, of taking off and landing with the prototype, gave SpaceX necessary data for developing the software and hardware that would later guide rocket stages back to earth. The tests took place at a facility in McGregor, Texas.

The next prototype was built around a second generation Falcon 9 tank. It was 40 meters tall with retractable legs. Its first test was a success and it flew more than 1,000 meters into the air before landing, however on its second test, a sensor was blocked, which caused strong winds to push it off course. An automatic process caused it to self-destruct before it drifted outside of the safe testing area. 

The first time SpaceX attempted to land a rocket’s stage was before the Falcon 9 tests. It was during SpaceX’s first completely commercial mission, launching a Canadian satellite called Cassiope into orbit. The launch was successful, however the first stage of the rocket lost control during the descent, and plunged into the ocean.

The next Falcon 9 rocket launched with the intent of landing, was on April 18, 2014. It was the first mission that an operational Falcon 9 flew with landing legs attached. Its landing was largely successful, however it was slightly off target, and plunged into the ocean, instead of landing on the platform.

On July 14, 2014, another Falcon 9 was launched, carrying cargo to the International Space Station. The delivery was a success. The rocket was launched without landing gear, as it was not intended to land. The first stage fell back into the ocean after detaching, but it slowed itself enough that it hit the ocean slowly. The rocket was used as a test, to see if it could slow down enough, to potentially land safely. It proved that the Falcon 9 rocket could reenter the atmosphere at super-sonic velocities, restart the main engines twice, and hit the surface slowly.

SpaceX often lands spent rocket stages on remotely controlled ships. These drone ships are large mobile floating platforms. Landing rockets at sea is an important capability, because if a rocket malfunctions, there isn’t anything that could be damaged nearby. If the rocket is off course, it will merely land in the sea, and be lost.

On January 10, 2015, a Falcon 9 attempted to land on a drone ship. The hydraulic fans controlling it’s decent stuck, and it flew out of control and crashed. Two months later, a Falcon 9 was launched, with a delivery of supplies and instruments to the International Space Station. The first stage was supposed to land on a drone ship, however a sticky valve prevented it from shutting off the engine in time, which caused it to fall over and explode.

A Falcon 9 rocket was launched from Cape Canaveral on December 22, 2015. It was SpaceX’s second launch for the company Orbcomm. The rocket took-off, and flew straight up to the edge of the atmosphere, and the first stage detached and came back down, and landed, marking the first successful landing of a used rocket stage. It was a vertical take-off launch. The term VTVL is often used now, for vertical take-off, vertical landing.

The next attempted landing, was onto a drone ship on January 7, 2016. However it was a failure, as one of the rocket legs failed to lock into place when it opened, and the rocket fell over, and exploded. There was another failed landing on March 4, 2016, as the rocket didn’t have enough fuel left over to slow itself down. The rocket didn’t have enough fuel because it had to deliver the satellite into a much higher orbit than usual. It crashed into the landing platform while moving too quickly, and exploded.

The first successful landing onto a drone ship took place on April 8, 2016. After a mission to the ISS, the rocket landed. It was later re-flown, which made it the first ever orbital rocket to be reused. A month later another rocket is successfully landed on a drone ship after delivering a satellite into a geostationary orbit.

As the technology for reusable rocket stages was perfected, Elon Musk started building all of his rockets with reuse in mind. SpaceX recovered every single rocket launched in 2017.

The Falcon 9 and Falcon Heavy Rockets

SpaceX’s most used rockets, the Falcon 9 and the Falcon 9 Heavy.

SpaceX uses two different kinds of launch vehicles, the Falcon 9, and the Falcon Heavy. The Falcon 9 is a two-stage rocket. The Falcon 9 rocket is designed to launch satellites or the dragon capsule, another creation of SpaceX. The Falcon 9 is 12 feet in diameter, 230 feet tall and weighs 1,207,920 pounds. It can deliver a payload of 50,000 pounds to a low earth orbit, a payload of 18,000 pounds to a geosynchronous orbit, or a payload of 8,800 pounds to Mars. It was designed to be easily reusable. Having only two stages minimizes the separations. The first stage has 9 engines, that are positioned so that even if two of them fail, the rocket can still complete its mission. The tanks are composed of an alloy of aluminum and lithium. It uses liquid oxygen and RP-1 (refined petroleum) as fuel. The rocket generates around 1.7 million pounds of thrust, at sea level and 1.8 million as it exits the atmosphere[7]. The difference in thrust comes from atmospheric pressure. The atmospheric pressure counteracts the pressure from the rocket’s combustion, causing less thrust to be produced.

The second stage of the Falcon 9 rocket is only powered by a single Merlin vacuum engine. Its purpose is to deliver the payload into the desired orbit, once the rocket is already in space. The tanks are made of the same aluminum-lithium alloy as the first stage. The second stage can be restarted multiple times if it is carrying multiple payloads that require different orbits[7]. 

The Falcon Heavy rocket is designed for much heavier payloads. It is the most powerful operating rocket today, by a factor of 2. Its total width, is 40 feet, and it is 230 feet tall. It has 2 stages, and 2 boosters. It weighs 3,125,735 pounds. It can deliver a payload of 140,000 pounds to low Earth orbit, 58,800 pounds to geosynchronous orbit, 37,000 pounds to Mars, or even 7,700 pounds as far as Pluto. The rockets are built with a 40% safety margin, meaning that they can withstand forces up to 40% greater than the maximum planned.

The first stage of the Falcon Heavy is made up of three cores. There are two cores on opposite sides of the center core. The side cores are connected to the center core at the top and bottom. Each core is very similar to the Falcon 9 rocket, with aluminum-lithium tanks and 9 Merlin engines. At liftoff all three cores fire at full thrust, but shortly after liftoff, the center core throttles down while the booster cores keep firing at full thrust. Once the booster cores separate and land, the center core throttles back up to full thrust.

The second stage is almost identical to the second stage of the Falcon 9, with a single Merlin engine and aluminum-lithium tanks. Its purpose is also the same.  Both rockets rely on the Merlin engine, which was developed by SpaceX. 

When launching a rocket, the primary difficulty isn’t lifting the rocket into space, it’s accelerating the rocket to orbital velocity. Orbital velocity differs depending on the distance from the earth. The orbital velocity for a low Earth orbit is 17,000 miles per hour. Low Earth orbit is an orbit centered around 1,200 miles from the surface of the Earth. Orbital velocity decreases as you get farther from the Earth. The equation used to calculate orbital velocity is SQRT((G*M)/R). G is the gravitational constant, M is the mass of the central body, and R is the radius of the orbit.

Because of orbital velocity, the location for launches is very important. Launch sites all tend to be near the equator, to take advantage of the fact that the Earth rotates. At the equator, the Earth is moving at about 1,000 miles per hour. That means the rockets launched on or near the equator start out traveling at 1000 miles per hour, meaning they need to accelerate less to achieve an orbit.

SpaceX’s Launch Sites

SpaceX’s South Texas (Boca Chica area) launch site. Photo from SpaceX.

SpaceX owns several different launch locations, all very far south in the USA. There is one in Texas, two in Florida, and one in California.

The launch site in Texas is called the SpaceX South Texas Launch Site. It is located in the Boca Chica area at the southern end of Texas. It is suited for orbital launches, as it is as close to the equator as you can get in the United States. Being close to the equator takes advantage of the lessened acceleration requirements. It is also far from any populated area, so in the event of a failed launch, the risk of injury is minimal.

Launch complex 39A is located near the Kennedy Space Center. Launch complex 39A was the site of many historic launches, including the Apollo missions, and Skylab. SpaceX has made numerous changes to the launch site, to support launches of larger rockets, such as the Falcon Heavy these changes include a greatly expanded hangar and reinforced launchpad. SpaceX also benefits from already existing local infrastructures, that supported the previous launches there. These include weather monitoring, ground support, payload processing facilities, and long-range tracking cameras.

SpaceX owns another launch site in Florida, on Cape Canaveral, Space Launch Complex 40 (SLC-40). It is in the Cape Canaveral Air Force Station, with Patrick Air Force Base to the south and NASA’s Kennedy Space Center to the north. Because of the proximity to other launch sites, SLC-40 benefits from many of the same services that they do, be it for fuel, parts, security, location, or weather monitoring services.

SpaceX’s Plans for the Future

Artist’s conception of a BFR approaching the Red Planet.

SpaceX has many ambitious plans for the future. One such plan is the Starship. The Starship is collectively the cargo carrying Starship spacecraft and its launch vehicle, the Falcon Super Heavy.  The Starship is designed to be able to carry crew along with cargo.

The Falcon Super Heavy rocket will carry the Starship. It will be 223 feet tall, and 30 feet in diameter. It will be able to generate 16 million pounds of thrust, and will carry 6.6 million pounds of propellant. Both the Starship and Falcon Super Heavy will use Raptor engines instead of Merlin engines. The Falcon Super Heavy will use 37 Raptor engines while the Starship stage will use 7. Raptor engines will be larger and run on liquid methane, rather than RP-1. This is because RP-1 can cause problems with residue build-up, in a process that is known as coking. Another reason methane will be used, is because it is theorized that methane could be extracted from the surface of Mars, making re-fueling the Starship possible on Mars.

SpaceX’s Competitors

There are companies other than SpaceX that are expanding into commercial spaceflight, and making their own innovations. Some of the more notable examples are Boeing, Sierra Nevada Corporation, Virgin Galactic, Xcor Aerospace, and Made in Space.

Boeing manufactures and sells airplanes, rotor-craft, rockets, satellites, missiles, and telecommunications equipment. Their scope has only recently expanded to include rockets. The rocket they developed is the CST-100 (Crew Space Transport – 100) or Boeing Starliner. They have yet to sell any, as the rockets are still in the development and testing phase. It is designed to carry up to 7 passengers, and would be viable to orbit for up to 7 months, and reliable for 10 launches. It is also designed to be compatible with other launch vehicles such as the Atlas V, Delta IV, Falcon 9, and Vulcan.

Another company that competes with SpaceX is the Sierra Nevada Corporation. They cover other areas than space-craft, such as national security and defense. One of their major projects is the Dreamchaser. It is designed to be launched from any conventional rocket, and can deliver up to 12,000 pounds of cargo. Like the Boeing Starliner, it is still in development, and has not yet been put into commercial use.

Launch Statistics

SpaceX has made a total of 91 launches, as of March, 2020. This includes 83 Falcon 9 launches, 3 Falcon Heavy launches, and 5 Falcon 1 launches. SpaceX has only failed a total of 5 launches, 3 of which were from the early testing and development of the Falcon 1. The most launches in one year, was during 2018, when a total of 21 rockets were launched, 9 new Falcon 9 rockets, 11 previously used Falcon 9 rockets, and one Falcon Heavy. 2020 is planned to be a close second, with 20 launches. There have already been 6 used Falcon 9 launches as of March, 2020. SpaceX has successfully landed 50 cores, or the first stage.

SpaceX has launched a total of 343,223 kilograms, or 756,677 pounds, of payload into various orbits. The majority of this was launched into a geostationary transfer orbit. This is an orbit designed to transfer from one orbit, to another, in the same plane, using the minimum amount of fuel possible. Another large portion of the launches were into polar orbits. Recently SpaceX has been doing mostly LEO (low earth orbit) launches.

SpaceX has a wide range of customers. Most of the launches are commercial, but many are for public agencies such as NASA, USAF and NRO. 60% of the launches are commercial, while 25% are for NASA, 1% and 2% from the NRO (National Reconnaissance Office) and USAF (United States Air-Force) respectively. SpaceX has performed 67 launches for commercial sources, 28 for NASA, 3 for the USAF, and 2 for the NRO. SpaceX has launched 10 rockets for its own purposes, or 9% of its total launches. SpaceX employs 7,000 people and was founded more than 18 years ago.

Plans to Colonize Mars

SpaceX has many goals that seem like near impossibilities. Probably the most notable of these is SpaceX’s claim that it will put people on Mars, by 2025. SpaceX plans to accomplish this using the Big Falcon Rocket (BFR), which is still being developed. SpaceX plans to launch a BFR carrying a Starship, into orbit by 2020 or 2021. This is the technology that will be used to transport crew and cargo to Mars. SpaceX plans to launch two loads of cargo to Mars, by 2022. This is because Mars’s orbit only brings it relatively close to the Earth once every two years. The rockets are planned to land on Mars by late 2022, or 2023. These launches would be carrying cargo necessary for the future base on Mars, such as tools and materials to construct habitats, generate power, and gather water. They also plan to make use of methane found on Mars, to potentially power return flights[12].

There is nothing planned for Mars in the year 2023, however SpaceX plans to fly Yusaku Maezawa around the Moon. Yusaku Maezawa is a Japanese billionaire who bought SpaceX’s services. It will be the first time that SpaceX has sent anyone to the moon, and Maezawa will be the thirteenth person to ever visit the moon[12].

In 2024, SpaceX plans to launch another BFR with a human crew, bound for Mars. SpaceX is unsure if it will need multiple launches or not, as the supplies needed to survive on Mars might be too much for a single launch, even with the previously delivered supplies from 2022. SpaceX plans to have the first people set foot on Mars in 2025, with the spaceships serving as temporary homes for the astronauts. By sometime in 2028 SpaceX plans to have completed the first Mars base, known as Mars Base Alpha. Mars Base Alpha would contain only the necessities to survive, but it will expand from there. From this point on, everything is less sure, but SpaceX projects that they may have a rudimentary city built on Mars by 2030[12].

Conclusion

It is important to stop and think about the amazing accomplishments SpaceX has made, bringing topics that were mere science fiction into reality. Landing and reusing rockets was never even considered before SpaceX accomplished it. They have even created a plan to colonize Mars. SpaceX is an amazing company that has completely changed the spaceflight industry.

References

[1] = https://www.spacex.com/about 

[2] = https://www.biography.com/business-figure/elon-musk 

[3] = https://www.whereisroadster.com/spacex/ 

[4] = https://www.oakton.edu/students/8/iiliev5728/Final%20Progect/SpaceX.htm 

[5] = https://www.nytimes.com/interactive/2018/science/spacex-falcon-launch.html 

[6] = https://qz.com/1016072/a-multimedia-history-of-every-single-one-of-spacexs-attempts-to-land-its-booster-rocket-back-on-earth/ 

[7] = https://www.spacex.com/falcon9 

[8] = https://www.spacex.com/falcon-heavy 

[9] = https://www.physicsclassroom.com/class/circles/Lesson-4/Mathematics-of-Satellite-Motion

[10] = https://www.fastcompany.com/3026685/the-worlds-top-10-most-innovative-companies-in-spacSe 

[11] = https://www.sncorp.com/

[12] = https://www.businessinsider.com/elon-musk-spacex-mars-plan-timeline-2018-10#2028-finish-building-mars-base-alpha-10

Radio Astronomy

Radio astronomy is a way of looking at extraterrestrial objects using the radio waves that they emit or reflect.

Radio waves are part of what is known as the electromagnetic spectrum. The electromagnetic spectrum contains all the different frequencies of electromagnetic radiation, of which visible light is a small part, specifically 4 *10^14 to 7*10^14 hertz (7.5*10^-07 to 4.3*10^-7 meters). As you dip below the range of visible light you get into the range of infrared light. Infrared light is the range of the electromagnetic spectrum between 7*10^14 hertz ( 4.3*10^-7 meters) and 10^13 hertz (3*10^-5 meters). Once below infrared, there is microwave radiation. Microwaves continue from 10^13 to 3*10^11 hertz (3*10^-5 to 1*10^-3 meters). Any electromagnetic radiation with a frequency below 3*10^11 hertz (1*10^-3 meters) is considered radio waves. They have a wavelength of at least 1 millimeter(“The EM Spectrum”).

The first form of electromagnetic radiation outside of the visible spectrum was discovered in the year 1800 by Sir William Herschel. He performed an experiment in which he separated light with a prism. He then placed thermometers in each distinct color of light, including one above and below the visible light. The thermometer that was outside of the visible light, on the red end, measured the highest temperature, though it seemed to be wholly outside of the light. It was this experiment that first showed the existence of infrared radiation(NASA).

The theory of electromagnetism was proposed in 1873, by the Scottish physicist, James Clerk Maxwell. He determined that there were four main electromagnetic interactions. The first is that the force of attraction or repulsion between electric charges is inversely proportional to the square of the distance between them, the second is that magnetic poles come in pairs that attract the opposite pole and repel like poles, the third is that an electric current in a conductor produces a magnetic field, the poles of the field being determined by the direction of the current, and the fourth is that moving an electric field relative to a conductor produces a magnetic field, and vice versa (Lucas, “Electromagnetic Radiation”).

The theory of electromagnetism by Maxwell predicted the existence of radio waves, and in 1886, Heinrich Hertz, a German physicist, used Maxwell’s theories to produce and receive radio waves. Maxwell used an induction coil and a Leyden Jar to produce the radio waves he detected. Hertz was the first person to transmit and receive radio waves, and the basic SI unit of frequency, the hertz, was named in his honor, as one electromagnetic cycle per second(Lucas, “Radio Waves”).

Sir Oliver Lodge was the first person to attempt to detect radio waves from an extraterrestrial source. He was conducting experiments on the propagation and reception of electromagnetic waves. He went on to create the “trembler”. It was a device based on the work of the French physicist Édouard Branly, who showed that loose iron filings react to electromagnetic waves inside of a glass tube. Lodge’s trembler used the shaking of iron filings to detect Morse code carried by electromagnetic radiation(Britannica). During his experiments with electromagnetic radiation, Lodge viewed the Sun as a possible source for radio waves. He attempted to detect them in the centimeter wavelengths, but though he failed, he was still the first one to try.

Many attempts were made to detect radio waves from extraterrestrial sources, but none were successful until 1931. Karl Jansky, while working for Bell Laboratories, tried to determine the source of  radio interference that was present around 20 MHz. Jansky built a large steerable antenna that would receive in wavelengths of 5 to 30 meters, or 15 to 30 MHz frequency. The antenna allowed him to locate the sources of static. He found three distinct sources, local thunderstorms, distant thunderstorms, and a steady hiss of static that was coming from the center of the Milky Way galaxy, as he showed using the source’s position in the sky (“UREI-Radio Astronomy Tutorial-Sec.4”).

Jansky’s findings were largely ignored for quite a while. It wasn’t until 1937, when Grote Reber read Jansky’s work that there were any major advancements. Reber was an electronics engineer, and an avid radio amateur. After reading Jansky’s work, Reber built the first real radio telescope, to which most telescopes today are very similar. It was a 9.5 meter parabolic reflector dish that he built alone in his backyard. He spent years studying radio emissions of varying wavelengths until he detected celestial emissions at a wavelength of 2 meters. Reber confirmed that the emissions were from the galactic plane, and continued to observe various radio sources until in 1944 he published the first radio frequency sky maps. His telescope is still on display today at the Green-Bank Observatory, in Green-Bank, West Virginia(“UREI-Radio Astronomy Tutorial-Sec.4”).

The first radio emissions from the Sun were discovered in 1942 by J.S. Hey, who was working with the British Army Operational Research Group to analyze occurrences of radio jamming of Army radar sets. There was a system for observing and recording potential jamming signals, which led Hey to conclude that the sun was emitting intense radio waves. It was later in the same year that G.C. Southworth  made the first successful observations of thermal radio emission from the sun at centimeter wavelengths, a frequency of less than 30 GHz(“UREI-Radio Astronomy Tutorial-Sec.4”).

The next major discovery was in 1963 when Bell Laboratories assigned Arno Penzias and Robert Wilson the task of tracing a radio noise that was interfering with the development of communication satellites. They discovered that no matter what direction they pointed the antenna, it would always receive the interference even where the sky was visibly empty. They had discovered cosmic background radiation, an ambient radiation that is always present. It is now widely believed that  cosmic background radiation is energy that remains from the creation of the universe. Wilson and Penzias went on to win the Nobel Prize for their discovery in 1978 (“UREI-Radio Astronomy Tutorial-Sec.4”).

A typical radio telescope consists of several different parts. They are the antenna, the reflector dish, the amplifier, and the computer that receives, records and processes the data. The  dish is used to reflect and focus the radio waves onto the antenna. The antenna of a radio telescope, at the focal point of the dish, receives the radio waves and converts them to electricity. The resulting electrical signals are sent to the amplifier, which as the name implies, amplifies the signal. Once the signal has been amplified it is usually sent to a computer where it is processed and recorded. Many telescopes are also mounted on a base that allows for movement, so they can be aimed at different parts of the sky(“Design of a Radio Telescope”).

The structure of radio telescopes haven’t changed much since the one that Reber built. Perhaps the largest advancement is telescope arrays. An array is many smaller radio telescopes that have been linked together. The multiple telescopes create an effect similar to having a single telescope with a dish radius as large as the radius of the array. This is due to the different positions from which each telescope views the sky, causing them to receive the same signals that a single dish would if it extended as far as the array. There are many problems with building a large single dish telescope. It would be very hard to build, as it would require an immense amount of materials and have difficulty supporting its own weight. An array has some drawbacks of its own, such as the light gathering abilities of an array are worse than what they would be if it was a single dish telescope of the same size, as light gathering abilities are determined by the total area covered. Another advantage of arrays is that many smaller telescopes are much easier to direct than a large one.

One example of a telescope array is the Very Large Array, or VLA, in New Mexico. It is composed of 28 separate dishes and antennas. Each dish is 82 feet wide and has 8 receivers. They are all steerable. They are arranged in a “Y” shape that varies in size, because the telescope are all on rails, making them mobile to adjust the size of the array. The array is half a mile to 23 miles across, depending on where the telescopes are on the rails(“Very Large Array”). It operates in frequencies from 1 to 50 GHz. The surfaces of the dishes are made of aluminum panels.  The VLA has made and contributed to many interesting discoveries, such as ice on Mercury, study of black-holes, and the center of our galaxy. It also observed an effect predicted by Einstein, Einstein rings. These are rings of electromagnetic radiation that have been distorted through intense gravity of massive objects such as black-holes.

One of the largest single dish telescopes is the Arecibo Observatory, in Puerto Rico. It is called the National Astronomy and Ionosphere Center (NAIC) and was built in 1960, in Arecibo, Puerto Rico. It is built into a volcanic crater and has a 305 meter wide reflector dish. The antenna is suspended above it by cables and can be moves to track different parts of the sky. The antenna of the telescope is also unusual. It is a dome that contains multiple reflecting dishes that further focus the radio waves. This is done so that the antenna can be mobile, to aim the telescope, as the dish is stationary. The Arecibo telescope discovered the first extra-solar planets. It was also used to produce detailed radar maps of the surface of Venus and Mercury, and discovered the first binary pulsar.

The EHT (Event Horizon Telescope) array covers the largest distance of any array. It is composed of 10 different telescopes and arrays around the world. Due to the spread of its components it has an effective aperture the size of the earth, which gives it the highest angular resolution possible on the surface of the earth. The Atacama Pathfinder Experiment (APEX), an array that is a collaboration between the Max Planck Institut für Radioastronomie (MPIfR), the Onsala Space Observatory (OSO), and the European Southern Observatory (ESO) is one part of the EHT array. The 30-meter telescope on Pico Veleta in the Spanish Sierra Nevada, the James Clark Maxwell Telescope operated by the East Asian Observatory, the Large Millimeter Telescope Alfonso Serrano built on the summit of Volcán Sierra Negra, the Sub-millimeter Array (SMA) located near the summit of  Mauna Kea in Hawaii, the Atacama Large Millimeter Array (ALMA) in Chile, and the South Pole Telescope (SPT) all make up the worldwide EHT array (“Array”).

The EHT array has been used to monitor black holes. It has watched the black-holes SgrA at the center of the Milky Way and M87 in the center of the Virgo A galaxy. It has been studying the validity of many theories about the mass of black holes, the event horizon, gravitational lensing, and possible emissions. The silhouettes of the black-holes matched predictions. In 2019, the EHT also managed to take a direct picture of the silhouette of the black-hole in the center of our galaxy, SgrA.

Radio telescopes have made many discoveries and observations. One such observation is the imaging of asteroids. Scott Hudson and Steven Ostro were the first people to image an asteroid. They imaged the peanut-shaped asteroid 4769 Castalia using the Arecibo observatory in 1989.

Another discovery is that of millisecond pulsars. The discovery was made in 1983, by Donald C. Backer, Miller Goss, Michael Davis, Carl Heiles and Shrinivas Kulkarni at the Arecibo telescope. A millisecond pulsar is one with a very fast rotational period. The one discovered is known as PSR B1937+21, and spins about 641 times a second. Since this discovery nearly 200 more have been discovered (Maggio).

One of the many applications for radio astronomy has been in the search for extraterrestrial intelligence. The term most commonly used for scientific pursuits of extraterrestrial life is SETI (Search for ExtraTerrestrial Intelligence). SETI has involved many arrays and telescopes around the world. There are also several projects that allow people to help observe the sky and donate idle processing power to analyzing the radio signals. SETI has not found any definite signs of other intelligent life, but it has detected signs that may indicate other intelligent life, such as the WOW signal. The WOW signal was an unusual burst of electromagnetic radiation, as if another planet was sending out radio bursts in the chance that someone detects them as we are.

Mercury’s rotational period was determined by radio telescopes. Using the Arecibo telescope, in 1964, Pettengill found that Mercury actually completed a full rotation every 59 days. It had long been thought to be tidally locked, maing the rotational period the same as the orbital, at 88 days (Maggio).

Binary pulsars were also discovered through radio astronomy. They were discovered in 1974. A binary pulsar is a pulsar with a white dwarf or neutron star orbiting it (Maggio).

In 2008, Arecibo was used to detect organic molecules in a starburst, an unusually fast developing star system that consumes available gases much more quickly than normal, 250 million light-years from Earth. Methanimine., a carbon based molecule (CH3N), and hydrogen cyanide (HCN) were discovered in the starburst Apr 220, which lies in the constellation Serpens. The discovery of organic molecules is very important for the possibility of life in other solar systems (Maggio).

Another very important discovery of radio telescopes is that of exoplanets. An exoplanet is any planet that exists outside of our solar system. On January 9, 1992, the astronomers Alex Wolszczan and Dale Frail, using the Arecibo telescope, discovered exoplanets orbiting a pulsar named PSR 1257+12. It is 2,300 light-years away in the constellation Virgo (“Top Astronomical Discoveries”).

Radio astronomy has made many interesting discoveries, and given rise to many theories.  It has been used for many different purposes, from photographing the event horizon of black-holes to searching for extraterrestrial life. It will likely continue to be enlightening and interesting into the future as it has been for the past 90 years

Have a question?


Works Cited

NASA, NASA, imagine.gsfc.nasa.gov/science/toolbox/history_multiwavelength1.html.

The EM Spectrum, labman.phys.utk.edu/phys222core/modules/m6/The EM spectrum.html.

A Brief History of Radio Astronomy, www.astronomytoday.com/astronomy/radioastro2.html.

UREI-Radio Astronomy Tutorial-Sec.4, www.haystack.mit.edu/edu/undergrad/materials/tut4.html.

Design of a Radio Telescope, www.sas.upenn.edu/~patann/RadioTelescopeDesign.htm.

“Array.” Event Horizon Telescope, eventhorizontelescope.org/array.

Britannica, The Editors of Encyclopaedia. “Sir Oliver Joseph Lodge.” Encyclopædia Britannica, Encyclopædia Britannica, Inc., 8 June 2019,               

Lucas, Jim. “What Are Radio Waves?” LiveScience, Purch, 27 Feb. 2019, 

Lucas, Jim. “What Is Electromagnetic Radiation?” LiveScience, Purch, 12 Mar. 2015, 

Maggio, Patricia K. “The Top Five Discoveries Made by Radio Telescopes.” Sciencing, 2 Mar. 2019, sciencing.com/top-discoveries-made-                  radio-telescopes-7566858.html.

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“Very Large Array.” National Radio Astronomy Observatory, public.nrao.edu/telescopes/vla/

The Loon Adventure

On Sunday [May 28, 2018], as my family was coming back from church, we noticed some commotion by the side of the road.  There were people by the side of the road looking at an apparently injured loon.  Someone had called Joel Rosenthal, who runs an animal sanctuary.  Joel’s animal sanctuary is only accessible, by vehicle, by fording the Greenbrier River.  It had been raining fairly hard for the past few days and the river was very high.  Joel misread a river gauge, thinking the river was low enough to safely cross, and decided to cross the river and take the loon from us.  My Dad and Abram, my older brother, put the loon into a feed-sack we had in the back of the car, with its head sticking out, and bound the bag shut with string so that the loon wouldn’t escape.  We then drove to the ford where Joel had crossed with a large Unimog.  Unimog is a brand of truck with very high ground clearance.  This Unimog had a front-end loader, and had water streaming out of the bucket from its recent crossing.  Joel took the loon and started to cross the river.  As he went, the engine started to run slower and slower as the Unimog went through the swollen river, until about 15 feet from the opposite shore the engine stalled, stranding both Joel and the loon.

        Dad and Abram drove off to try to find a canoe, while the rest of us stayed behind to watch Joel. Joel managed to swim safely to shore.  Dad and Abram drove to our mother’s house and borrowed a canoe.  Upon returning Dad tied the canoe to a tree with a long rope to test if Abram and he could paddle across.  Dad and Abram could not handle the canoe well enough, and Dad decided that it would be too dangerous to cross by canoe.  Dad and Abram, returned to shore and we drove home.  Since we couldn’t get to Joel’s from that side of the river we decided to try to get to Joel’s place, usually described as accessible only by fording the river, from the other side of the river.  That night Dad looked at maps and talked to people who knew the area.  We planned to set out the next morning.

        In the morning we set out to reach Joel’s. On the way we bought a topographic map.  The closest vehicular approach on the map, to Joel’s property, on that side of the river was about three miles, but that road had been closed.  We drove to the next closest approach, that appeared to be about 6 miles from Joel’s property on the map.  The proposed route was to climb over Pond Ridge and follow Oldham Run to Joel’s property, but someone who knew the area had advised us to walk on top of Pond Ridge to avoid the thick rhododendron growth next to Oldham Run.  We began walking.  We crossed a stream and climbed up what we thought was Pond Ridge.  When we reached the top, we consulted the map that we had purchased earlier, and discovered that it was not Pond ridge, but only a knob at the end of it.  Abram, Dad and I climbed up, then down two more steep hills and up again, until we finally climbed to the top of Pond Ridge.  Dad decided that Pond Ridge was too difficult to follow because it wasn’t a straight flat ridge. It bent, dipped and curved and would be very difficult to stay on, so we followed a dry stream course down to Oldham Run and decided to brave the rhododendron thickets.  Oldham Run had thick rhododendron growth on both sides of it as promised.  For about five of the six miles we walked up and down the sides of the extremely steep valley and sometimes crawled on our hands and knees through the rhododendron thickets.

         We got tired and stopped to eat lunch roughly 2/3 of the way through.  Eventually the valley widened, and the rhododendron was only near the stream course.  We found several old railroad grades and the walking became much easier on the flat ground, with little to no rhododendron, for the last one or two miles.  It took us five and a half hours to get to Joel’s property.

        Once at Joel’s we needed to get the loon out of the truck.  The river had gone down a lot during the night and was only waist height.  Abram waded out, attached to a rope, to the Unimog and got the loon out.  The loon had not died during the night from stress or fallen off the seat and drowned.  Joel looked the loon over and could find nothing wrong with it.  We took the loon to a pond and released it.  It dipped under the water and splashed around and went to the other side of the pod.  It began fishing and staying clear of us.  It was uninjured, so we inferred that the loon had made a mistaken landing on the wet pavement and was unable to take off again.  We were tired from our long walk, and we decided to get the Unimog out of the river tomorrow.  

        The following morning, we pulled the Unimog out of the river. Joel had a lot of heavy equipment, but most of it did not run. The largest easily available vehicle was a four-wheel drive Kubota tractor.  We drove it to the river and tried to pull the Unimog out.  Dad stood on the back of the Kubota tractor and chained it to the Unimog.  The tractor tried but could not pull the truck out.  It dug large ruts in the river bottom and nearly got itself stuck.  As the tractor drove out of the river, we saw it spitting a thick white liquid out of the engine breather.   Dad explained that the engine oil and water that had leaked in from the river, had been churned together into a thick liquid that had the consistency of a milkshake.  We drove the Kubota back to a building and immediately changed the oil to prevent the engine from destroying itself without proper oil.  The oil in the tractor was still mixed with water, but it was good enough to run for a while after we drained a lot of the water-oil out of it and put new oil into it. 

 Dad and Joel drove the Kubota across the river to get a bulldozer to pull the Unimog out.  It took Dad half an hour of working on the battery of the bulldozer to start it.  After the bulldozer started, Dad drove the Kubota back to its enclosure, and Joel drove the bulldozer back to the Unimog, and pulled it out of the river easily. 

Once on dry land Dad began looking over the Unimog because it might have sucked water into the cylinders of the engine and destroyed itself.  After looking it over for a while, he began to slowly hand crank the engine.  After determining that there was no water in the cylinders he started it, and it ran fine.  Apparently, what had happened was the duck bill drain on the fuel filter had become old and cracked.  It had sucked in a mist of water that wet the filter.  The wet filter could not suck enough fuel through or the mist of water absorbed too much heat to allow fuel to ignite, causing the engine to stall.

        In the end, the loon was perfectly fine and so was the Unimog.  Joel drove us back across the river where my brother Michael met us to pick us up.  Michael drove us back to where we parked our car, and we drove home.  We were all satisfied that it had gone remarkably well.