Via advanced analyses, scientists shed light on the mechanism of a deadly problem plaguing combustion chambers in rocket engines
A vital piece of gas engines, combustors―the chambers in which the combustion powering the engine occurs―have the problem of breaking down due to fatal high-frequency oscillations during the combustion process. Now, through advanced time-series analyses based on complex systems, researchers from Tokyo University of Science and Japan Aerospace Exploration Agency have found what causes them, opening up novel paths to solving the problem.
Rocket engines contain confined combustion systems, which are, essentially, combustion chambers. In these chambers, nonlinear interactions among turbulent fuel and oxidizer flows, sound waves, and heat produced from chemical reactions, cause an unstable phenomenon called ‘combustion oscillations.’ The force of these oscillations on the body of the combustion chamber―the mechanical stress on the chamber― is high enough to threaten catastrophic failure of the engine. What causes these oscillations? The answer remains to be found.
Now, in a breakthrough, published in Physics of Fluids, a team including Prof. Hiroshi Gotoda, Ms. Satomi Shima, and Mr. Kosuke Nakamura from Tokyo University of Science (TUS), in collaboration with Dr. Shingo Matsuyama and Dr. Yuya Ohmichi from the Japan Aerospace Exploration Agency (JAXA), have used advanced time-series analyses based on complex systems to find out.
Explaining their work, Prof. Gotoda says, “Our main purpose was to reveal the physical mechanism behind the formation and sustenance of high-frequency combustion oscillations in a cylindrical combustor using sophisticated analytical methods inspired by symbolic dynamics and complex networks.” These findings have also been covered by the American Society of Physics in their news section, and by the Institute of Physics on their news platform Physics World.
The combustor the scientists picked to simulate is one of model rocket engines. They were able to pinpoint the moment of transition from the stable combustion state to combustion oscillations and visualize it. They found that significant periodic flow velocity fluctuations in fuel injector affect the ignition process, resulting in changes to the heat release rate. The heat release rate fluctuations synchronize with the pressure fluctuations inside the combustor, and the whole cycle continues in a series of feedback loops that sustain combustion oscillations.
Additionally, by considering a spatial network of pressure and heat release rate fluctuations, the researchers found that clusters of acoustic power sources periodically form and collapse in the shear layer of the combustor near the injection pipe’s rim, further helping drive the combustion oscillations.
These findings provide reasonable answers for why combustion oscillations occur, albeit specific to liquid rocket engines. Prof. Gotoda explains, “Combustion oscillations can cause fatal damage to combustors in rocket engines, aero engines, and gas turbines for power generation. Therefore, understanding the formation mechanism of combustion oscillations is an important research subject. Our results will greatly contribute to our understanding of the mechanism of combustion oscillations generated in liquid rocket engines.”
Indeed, these findings are significant and can be expected to open doors to novel routes of exploration to prevent combustion oscillations in critical engines.
Featured image: Representation of instantaneous flow velocity field during combustion oscillations in the combustion chamber of a model rocket engine: This figure shows that large-scale vortex rings are produced from the injector rim during combustion oscillations. Photo courtesy: Satomi Shima, Kosuke Nakamura, Hiroshi Gotoda, Yuya Ohmichi, and Shingo Matsuyama
Title of original paper: Formation mechanism of high-frequency combustion oscillations in a model rocket engine combustor
The increasing size of the private space industry could be a climate disaster as rockets emit vast quantities of propellant exhaust into the stratosphere and mesosphere, where it can persist for at least two to three years, warns Dr Eloise Marais (UCL Geography).
The commercial race to get tourists to space is heating up between Virgin Group founder Sir Richard Branson and former Amazon CEO Jeff Bezos. On Sunday 11 July, Branson ascended 80 km to reach the edge of space in his piloted Virgin Galactic VSS Unity spaceplane. Bezos’ autonomous Blue Origin rocket is due to launch on July 20, coinciding with the anniversary of the Apollo 11 Moon landing.
Though Bezos loses to Branson in time, he is set to reach higher altitudes (about 120 km). The launch will demonstrate his offering to very wealthy tourists: the opportunity to truly reach outer space. Both tour packages will provide passengers with a brief ten-minute frolic in zero gravity and glimpses of Earth from space. Not to be outdone, Elon Musk’s SpaceX will provide four to five days of orbital travel with its Crew Dragon capsule later in 2021.
What are the environmental consequences of a space tourism industry likely to be? Bezos boasts his Blue Origin rockets are greener than Branson’s VSS Unity. The Blue Engine 3 (BE-3) will launch Bezos, his brother and two guests into space using liquid hydrogen and liquid oxygen propellants. VSS Unity used a hybrid propellant comprised of a solid carbon-based fuel, hydroxyl-terminated polybutadiene (HTPB), and a liquid oxidant, nitrous oxide (laughing gas). The SpaceX Falcon series of reusable rockets will propel the Crew Dragon into orbit using liquid kerosene and liquid oxygen.
Burning these propellants provides the energy needed to launch rockets into space while also generating greenhouse gases and air pollutants. Large quantities of water vapour are produced by burning the BE-3 propellant, while combustion of both the VSS Unity and Falcon fuels produces CO₂, soot and some water vapour. The nitrogen-based oxidant used by VSS Unity also generates nitrogen oxides, compounds that contribute to air pollution closer to Earth.
Roughly two-thirds of the propellant exhaust is released into the stratosphere (12 km-50 km) and mesosphere (50 km-85 km), where it can persist for at least two to three years. The very high temperatures during launch and re-entry (when the protective heat shields of the returning crafts burn up) also convert stable nitrogen in the air into reactive nitrogen oxides.
These gases and particles have many negative effects on the atmosphere. In the stratosphere, nitrogen oxides and chemicals formed from the breakdown of water vapour convert ozone into oxygen, depleting the ozone layer which guards life on Earth against harmful UV radiation. Water vapour also produces stratospheric clouds that provide a surface for this reaction to occur at a faster pace than it otherwise would.
Space tourism and climate change
Exhaust emissions of CO₂ and soot trap heat in the atmosphere, contributing to global warming. Cooling of the atmosphere can also occur, as clouds formed from the emitted water vapour reflect incoming sunlight back to space. A depleted ozone layer would also absorb less incoming sunlight, and so heat the stratosphere less.
Figuring out the overall effect of rocket launches on the atmosphere will require detailed modelling, in order to account for these complex processes and the persistence of these pollutants in the upper atmosphere. Equally important is a clear understanding of how the space tourism industry will develop.
Virgin Galactic anticipates it will offer 400 spaceflights each year to the privileged few who can afford them. Blue Origin and SpaceX have yet to announce their plans. But globally, rocket launches wouldn’t need to increase by much from the current 100 or so performed each year to induce harmful effects that are competitive with other sources, like ozone-depleting chlorofluorocarbons (CFCs), and CO₂ from aircraft.
During launch, rockets can emit between four and ten times more nitrogen oxides than Drax, the largest thermal power plant in the UK, over the same period. CO₂ emissions for the four or so tourists on a space flight will be between 50 and 100 times more than the one to three tonnes per passenger on a long-haul flight.
In order for international regulators to keep up with this nascent industry and control its pollution properly, scientists need a better understanding of the effect these billionaire astronauts will have on our planet’s atmosphere.
“Super-Earth” planets are giant-size versions of Earth, and many researches suggested that they’re more likely to be habitable than Earth-size worlds. But, a study done by Hippke and colleagues revealed how difficult it would be for any aliens on these exoplanets to explore space.
Do we inhabit the best of all possible worlds? From a variety of habitable worlds that may exist, Earth might well turn out as one that is marginally habitable. Other, more habitable (“superhabitable”) worlds might exist. Planets more massive than Earth can have a higher surface gravity, which can hold a thicker atmosphere, and thus better shielding for life on the surface against harmful cosmic rays. Increased surface erosion and flatter topography could result in an “archipelago planet” of shallow oceans ideally suited for biodiversity. There is apparently no limit for habitability as a function of surface gravity as such. Size limits arise from the transition between Terran & Neptunian worlds around 2 ± 0.6 R. The largest rocky planets known so far are ∼ 1.87 R⊕, ∼ 9.7 M⊕ (Kepler-20 b, Buchhave et al. 2016). When such planets are in the habitable zone, they may be inhabited by “Super-Earthlings” (SEALs). Can Seals still use chemical rockets to leave their planet?
At our current technological level, spaceflight requires a rocket launch to provide the thrust needed to overcome Earth’s force of gravity. Chemical rockets are powered by exothermic reactions of the propellant, such as hydrogen and oxygen. Other propulsion technologies with high specific impulses exist, such as nuclear thermal rockets (e.g., NERVA, Arnold & Rice 1969), but have been abandoned due to political issues. Rockets suffer from Tsiolkovsky’s equation (Tsiolkovsky 1903): if a rocket carries its own fuel, the ratio of total rocket mass versus final velocity is an exponential function, making high speeds (or heavy payloads) increasingly expensive. While Hippke and colleagues hand-wave away many things in this paper, they do respect rocket science.
State-of-the-art technology such as the recently introduced Falcon Heavy has a rocket height of 70 m, mass of 1421 t, and delivers a payload of 16.8 t to an Earth escape velocity, so that the payload fraction is ∼ 1 %. Hippke and colleagues now explored how much rocket is needed for planets with higher surface gravity.
To explore this they employed a method which I explained below:
The achievable maximum velocity change of a chemical rocket is
where, m0 is the initial total mass (including fuel), mf is the final total mass without fuel (the dry mass), and vex is the exhaust velocity. Here, we can substitute vex = g0 Isp where g0 = G M⊕/R² ∼ 9.81 ms-¹ is the standard gravity and Isp is the specific impulse (total impulse per unit of propellant), typically ∼ 350 . . 450 s for hydrogen/oxygen.
To leave Earth’s gravitational influence, a rocket needs to achieve at minimum the escape velocity
for Earth, and vesc ∼ 27.1 kms-¹ for a 10 M, 1.7 R Super-Earth similar to Kepler-20 b.
They consider a single-stage rocket with Isp = 350 s and wish to achieve ∆v > vesc. The mass ratio of the vehicle becomes
which evaluates to a mass ratio of ∼ 26 on Earth, and ∼ 2,700 on Kepler-20 b. Consequently, a single-stage rocket on Kepler-20 b must burn 104× as much fuel for the same payload (∼ 2,700 t of fuel for each t of payload). This example neglects the weight of the rocket structure itself, and is therefore a never achievable lower limit. In reality, rockets are multistage, and have typical mass ratios (to Earth escape velocity) of 50 . . . 150. For example, the Saturn V had a total weight of 3,050 t for a lunar payload of 45 t, so that the ratio is 68. The Falcon Heavy has a total weight of 1,400 t and a payload of 16.8 t, so that the ratio is 83.
For a mass ratio of 83, the minimum rocket (1 t to vesc) would carry 9,000 t of fuel on Kepler-20 b, which is only 3× larger than a Saturn V (which lifted 45 t). To lift a more useful payload of 6.2 t as required for the James Webb Space Telescope on Kepler-20 b, the fuel mass would increase to 55,000 t, about the mass of the largest ocean battleships. They showed such a rocket to scale in Figure 1. For a classical Apollo moon mission (45 t), the rocket would need to be considerably larger, ∼ 400,000 t. Researchers are not sure how ridiculous such a rocket is, because it is still less heavy than the Pyramid of Cheops, although not by much.
So, as now you know how big Rockets aliens need. Lets see, how would different worlds launch their chemical rockets.
Friends, rockets work better in space than in an atmosphere. How about launching the rocket from a high mountain? At first glance, this is a great idea, because the rocket thrust is given by
where ˙m is the mass flow rate, Ae is the cross-sectional area of the exhaust jet, P1 is the static pressure inside the engine, and P2 is the atmospheric pressure. The exhaust velocity is maximized for zero atmospheric pressure, i.e. in vacuum. Unfortunately, the effect is not very large in practice. For the Space Shuttle’s main engine, the difference between sea level and vacuum is ∼ 25 %. Atmospheric pressure below 0.4 bar (Earth altitude 6,000 m) is not survivable long term for humans, and presumably neither for Seals. Then, the effect is ∼ 15%. Such low pressures are reached in lower heights on Super-Earths, because the gravity pulls the air down. Strongly.
Another effect which is to the SEALs disadvantage is that the bigger something is, the less it can deviate from being smooth. Tall mountains will crush under their own weight (the “potato radius” is ∼ 238 km). Therefore, Hippke and colleagues expect more massive planets to have smaller mountains. This will be detectable through transit observations in future telescopes.
Indeed, the largest mountains in our solar system are on less massive bodies. Researchers recommend that the SEALs use shovels to make a gigantic mountain, exceeding the atmosphere, and launch their rocket from the vacuum on top. Researchers encourage further research in this rather under-explored field.
Launching rockets from water-worlds
Many habitable (and presumably inhabited) planets might be waterworlds, & intelligent life in water & sub-surface is plausible. How would Nautical Super Earthlings (Navy SEALs) launch their rockets? This is actually less absurd than most other things in this paper, but harder than the reader might think.
An elegant method would be to build an Alien “megastructure”, as postulated by Wright in 2016. To launch the rocket, a large floating structure can be used. Turtles do not exist in such sizes, but nautical floats can be built in turtle shapes. The rocket would be placed on the turtle’s shield (out of the water), dried with towels, and then launched towards the heavens, while other (living) turtles spray water towards the launch pad turtle to cool down the hot exhaust fumes.
These minor aquatic launch complications make the theory of oceanic rocket launches appear at first quite alien; presumably land-based launches seem equally human to alien rocket scientists.
Launching rockets on worlds with an icy crust
Subsurface liquid water oceans exist below the frozen surfaces of Enceladus and Europa, and it appears plausible that such worlds are habitable. How would ice nautical Super-Earthlings (iNavy SEALS) launch their chemical rockets? They need an icebreaker.
One method which works (sometimes not so well) is to use classical explosives to flash-vaporize water into steam. The pressure of the expanding gas drives the missile upwards in a tube. This works well for comparably small ICBMs launched from submerged submarines, but these have no issues with ice coverage. As a minor annoyance, ice crusts on Europa and Enceladus are tens of kilometers thick. A series of fusion bombs could be used to blast through the ice and then, quickly, lift the massive rocket completely out of the water. This is highly non-trivial, because of the vacuum on the outside, which does not allow for a liquid phase of the water. The expanding vaporized fountain would re-freeze quickly, leaving little time for the journey.
Fortunately for the fellow iNavy-SEALS who must stay behind, water (H2O) cannot become radioactive itself, and radioactive particles are mostly not soluble in water. Therefore, they can be filtered out after the launch. Typical fallout particles sink to the sea floor in a few days, and in the meantime, drinking water can be drawn from near the top of the pool. Among the authors who have not pointed this out is Einstein (1905).
If there is no plutonium on the iNavy-SEALS’ world to build atomic bombs, researchers recommend to use “Occam’s Laser” to blast a hole in the ice. Earthlings will use it for ”Breakthrough Starshot”, a mission to α Cen. A km-sized phased aperture would emit 100 GW of laser power, sufficient to accelerate a 1 g “space-chip” to v = 0.2 c in minutes. Light sails are no rockets, and therefore not rocket science, therefore researchers recommend to use the laser to blast through the ice.
Another way to get out is to ascend through the plumes which spew from Enceladus’ south polar surface. For details, please refer the fig given below and Jules Verne (1864).
So, what is the amount of fuel required for different surface gravities?
Well, according to researchers, for a payload of one ton to escape velocity, the required amount of chemical fuel is ∼ 3.3 exp(g0). The situation is not that bad for medium-sized Super-Earths, but quickly escalates due to the nasty exponential function (who likes these anyways?). On worlds with a surface gravity of ≥ 10 g0, a sizable fraction of the planet needs to be used up as chemical fuel per launch, limiting the total number of flights. They showed in Figure 3 how ridiculous the amount of fuel is for worlds with even higher surface gravity. On such worlds it is cheaper to destroy the planet rather than convert it into fuel.
In the ultimate limit, we may use the whole mass of the universe (ordinary matter only) of ≈ 10^50 kg as oxygen/hydrogen fuel. Such a chemical rocket can overcome a surface gravity of ∼ 35.3 g0. For comparison, a neutron star’s density results in a very high surface gravity of ≈ 10^11g0. Pulsar-lings will thus not become chemically space-faring beings. If such a “universal chemical rocket” is launched from space directly, its final velocity would be ∼ 400 km s-¹, or ∼ 0.13% the speed of light. It has no trouble with interstellar dust, because its road to nowhere is free.
NASA’s Perseverance rover carries a device to convert Martian air into oxygen that, if produced on a larger scale, could be used not just for breathing, but also for fuel.
One of the hardest things about sending astronauts to Mars will be getting them home. Launching a rocket off the surface of the Red Planet will require industrial quantities of oxygen, a crucial part of propellant: A crew of four would need about 55,000 pounds (25 metric tons) of it to produce thrust from 15,000 pounds (7 metric tons) of rocket fuel.
That’s a lot of propellant. But instead of shipping all that oxygen, what if the crew could make it out of thin (Martian) air? A first-generation oxygen generator aboard NASA’s Perseverance rover will test technology for doing exactly that.
The Mars Oxygen In-Situ Resource Utilization Experiment, or MOXIE, is an experimental instrument that stands apart from Perseverance’s primary science. One of the rover’s main purposes is capturing returnable rock samples that could carry signs of ancient microbial life. While Perseverance has a suite of instruments geared toward helping achieve that goal, MOXIE is focused solely on the engineering required for future human exploration efforts.
Since the dawn of the space age, researchers have talked about in-situ resource utilization, or ISRU. Think of it as living off the land and using what’s available in the local environment. That includes things like finding water ice that could be melted for use or sheltering in caves, but also generating oxygen for rocket fuel and, of course, breathing.
Breathing is just a side benefit of MOXIE’s true goal, said Michael Hecht of the Massachusetts Institute of Technology, the instrument’s principal investigator. Rocket propellant is the heaviest consumable resource that astronauts will need, so being able to produce oxygen at their destination would make the first crewed trip to Mars easier, safer, and cheaper.
“What people typically ask me is whether MOXIE is being developed so astronauts have something to breathe,” Hecht said. “But rockets breathe hundreds of times as much oxygen as people.”
Making Oxygen Requires Heat
Mars’ atmosphere poses a major challenge for human life and rocket propellant production. It’s only 1% as thick as Earth’s atmosphere and is 95% carbon dioxide.
MOXIE pulls in that air with a pump, then uses an electrochemical process to separate two oxygen atoms from each molecule of carbon dioxide, or CO2. As the gases flow through the system, they are analyzed to check how much oxygen has been produced, how pure it is, and how efficiently the system is working. All the gases are vented back into the atmosphere after each experiment is run.
Powering this electrochemical conversion requires a lot of heat – about 1,470 degrees Fahrenheit (800 degrees Celsius). Because of those high temperatures, MOXIE, which is a little larger than a toaster, features a variety of heat-tolerant materials. Special 3D-printed nickel alloy parts help distribute the heat within the instrument, while superlight insulation called aerogel minimizes the power needed to keep it at operating temperatures. The outside of MOXIE is coated in a thin layer of gold, which is an excellent reflector of infrared heat and keeps those blistering temperatures from radiating into other parts of Perseverance.
“MOXIE is designed to make about 6 to 10 grams of oxygen per hour – just about enough for a small dog to breathe,” said Asad Aboobaker, a MOXIE systems engineer at NASA’s Jet Propulsion Laboratory in Southern California. “A full-scale system geared to make (propellant for the flight home) would need to scale up oxygen production by about 200 times what MOXIE will create.”
Video: MOXIE engineer Asad Aboobaker of JPL explains how the instrument works in this video interview. Credit: NASA/JPL-Caltech
The Future Martians
Hecht estimates that a full-scale MOXIE system on Mars might be a bit larger than a household stove and weigh around 2,200 pounds (1,000 kilograms) – almost as much as Perseverance itself. Work is ongoing to develop a prototype for one in the near future.
The team expects to run MOXIE about 10 times over the course of one Mars year (two Earth years), allowing them to watch how well it works in varying seasons. The results will inform the design of future oxygen generators.
“The commitment to developing MOXIE shows that NASA is serious about this,” Hecht said. “MOXIE isn’t the complete answer, but it’s a critical piece of it. If successful, it will show that future astronauts can rely on this technology to help get them home safely from Mars.”
More About the Mission
A key objective for Perseverance’s mission on Mars is astrobiology, including the search for signs of ancient microbial life. The rover will characterize the planet’s geology and past climate, pave the way for human exploration of the Red Planet, and be the first mission to collect and cache Martian rock and regolith (broken rock and dust).
Subsequent missions, currently under consideration by NASA in cooperation with ESA (the European Space Agency), would send spacecraft to Mars to collect these cached samples from the surface and return them to Earth for in-depth analysis.
The Mars 2020 mission is part of a larger program that includes missions to the Moon as a way to prepare for human exploration of the Red Planet. Charged with returning astronauts to the Moon by 2024, NASA will establish a sustained human presence on and around the Moon by 2028 through NASA’s Artemis lunar exploration plans.
JPL, which is managed for NASA by Caltech in Pasadena, California, built and manages operations of the Perseverance rover.
Guys, we all know about gravity which causes every object to pull every other object toward it. But, what about microgravity. Why it is so important in space. Why does NASA study it? There are many questions in your mind but today you will get all the answers.
So, let’s start with what is microgravity? It is the condition in which people or objects appear to be weightless. The effects of microgravity can be seen when astronauts and objects float in space. Microgravity can be experienced in other ways, as well. “Micro-” means “very small,” so microgravity refers to the condition where gravity seems to be very small. In microgravity, astronauts can float in their spacecraft – or outside, on a spacewalk. Heavy objects move around easily. For example, astronauts can move equipment weighing hundreds of pounds with their fingertips. Microgravity is sometimes called “zero gravity,” but this is misleading.
Some people think that there is no gravity in space. In fact, a small amount of gravity can be found everywhere in space. Gravity is what holds the moon in orbit around Earth. Gravity causes Earth to orbit the sun. It keeps the sun in place in the Milky Way galaxy. Gravity, however, does become weaker with distance. It is possible for a spacecraft to go far enough from Earth that a person inside would feel very little gravity. But this is not why things float on a spacecraft in orbit. The International Space Station orbits Earth at an altitude between 200 and 250 miles. At that altitude, Earth’s gravity is about 90 percent of what it is on the planet’s surface. In other words, if a person who weighed 100 pounds on Earth’s surface could climb a ladder all the way to the space station, that person would weigh 90 pounds at the top of the ladder.
If 90 percent of Earth’s gravity reaches the space station, then why do astronauts float there? The answer is because they are in free fall. In a vacuum, gravity causes all objects to fall at the same rate. The mass of the object does not matter. If a person drops a hammer and a feather, air will make the feather fall more slowly. But if there were no air, they would fall at the same acceleration. Some amusement parks have free-fall rides, in which a cabin is dropped along a tall tower. If a person let go of an object at the beginning of the fall, the person and the object would fall at the same acceleration. Because of that, the object would appear to float in front of the person. That is what happens in a spacecraft. The spacecraft, its crew and any objects aboard are all falling toward but around Earth. Since they are all falling together, the crew and objects appear to float when compared with the spacecraft.
What does it mean to fall around Earth? Earth’s gravity pulls objects downward toward the surface. Gravity pulls on the space station, too. As a result, it is constantly falling toward Earth’s surface. It also is moving at a very fast speed – 17,500 miles per hour. It moves at a speed that matches the way Earth’s surface curves. If a person throws a baseball, gravity will cause it to curve down. It will hit the ground fairly quickly. An orbiting spacecraft moves at the right speed so the curve of its fall matches the curve of Earth. Because of this, the spacecraft keeps falling toward the ground but never hits it. As a result, they fall around the planet. The moon stays in orbit around Earth for this same reason. The moon also is falling around Earth.
NASA studies microgravity to learn what happens to people and equipment in space. Microgravity affects the human body in several ways. For example, muscles and bones can become weaker without gravity making them work as hard. Astronauts who live on the space station spend months in microgravity. Astronauts who travel to Mars also would spend months in microgravity traveling to and from the Red Planet. NASA must learn about the effects of microgravity to keep astronauts safe and healthy. In addition, many things seem to act differently in microgravity. Fire burns differently. Without the pull of gravity, flames are more round. Crystals grow better. Without gravity, their shapes are more perfect. NASA performs science experiments in microgravity. These experiments help NASA learn things that would be hard or perhaps impossible to learn on Earth.
But, how do researchers create microgravity?
Well guys, researchers can create microgravity conditions in two ways. Because gravitational pull diminishes with distance, one way to create a microgravity environment is to travel away from Earth. To reach a point
where Earth’s gravitational pull is reduced to onemillionth cf that at the surface, you would have to travel into space a distance of 6.37 million kilometers from Earth (almost 17 times farther away than the Moon, 1400 times the highway distance between New York City & Los Angeles, or about 70 million football fields). This approach is impractical, except for automated spacecraft, because humans have yet to travel farther away from Earth than the distance to the Moon. However, freefall can be used to create a microgravity environment consistent with our
primary definition of microgravity.
But, are there any other methods? Or can you able to create microgravity on earth?? Yes, you can guys. How? Well, we already explained one above i.e. by using spacecraft. The others are elaborated below.
1) DROP FACILITIES
Researchers use high-tech facilities based on the elevator analogy to create micro-gravity conditions. The NASA Lewis Research Center has
two drop facilities. One provides a 132 meter drop into a hole in the ground similar to a mine shaft. This drop creates a reduced gravity environment for 5.2 seconds. A tower at Lewis allows for 2.2 second drops down a 24 meter structure. The NASA Marshall Space Flight Center has a different type of reduced gravity facility. This 100 meter tube allows for drops of 4.5 second duration. Other NASA Field Centers and other countries have additional drop facilities of varying sizes to serve different purposes. The longest drop time currently available (about 10
seconds) is at a 490 meter deep vertical mine shaft in Japan that has been converted to a drop facility. Sensations similar to those resulting from a drop in these reduced gravity facilities can be experienced on freefall rides in amusement parks
or when stepping off of diving platforms.
Airplanes are used to achieve reduced gravity conditions for periods of about 15 seconds. This environment is created as the plane flies on a parabolic path. A typical flight lasts 2-3 hours allowing experiments and crew members to take advantage of about forty periods of microgravity. To accomplish this, the plane climbs
rapidly at a 45 degree angle (this phase is called pull up), traces a parabola (pushover), and then descends at a 45 degree angle (pull out). During the pull up and pull out segments, crew and experiments experience accelerations of about 2
g. During the parabola, net accelerations drop as low as 1.5×10-² g for about 15 seconds. Due to the experiences of many who have flown on parabolic aircraft, the planes are often referred to as “Vomit Comets.” Reduced gravity conditions created by the same type of parabolic motion described above can be experienced on the series of “floater” hills that are usually located at the end of roller coaster rides and when driving over
swells in the road.
Sounding rockets are used to create reduced gravity conditions for several minutes; they follow suborbital, parabolic paths. Freefall exists during
the rocket’s coast: after burn out and before entering the atmosphere. Acceleration levels are usually around 10-5 g. While most people do not
get the opportunity to experience the
accelerations of a rocket launch and subsequent freefall, springboard divers basically launch themselves into the air when performing dives
and they experience microgravity conditions until they enter the water.