The newest addition to the International Space Station (ISS) could be launching as early as September 2015! Bigelow Expandable Activity Module (BEAM) is a combined effort of Bigelow Aerospace with NASA and SpaceX and it is exactly what it sounds like, an expandable space habitat that will find residence at the ISS for the next two years. In those two years, astronauts will be inspecting and gathering performance data to see if it really is a viable habitat that can resist the rigors of orbit including radiation, loads from accelerations, and even micrometeorites. When it is not being inspected, it will possibly serve as a lounge area for astronauts or as an additional laboratory and that’s really the beauty of it. It can be anything you want it to be, it’s more space in space! The keyword in its description is “expandable” as astronauts will activate a pressurization system and expand the BEAM to roughly the size of a 10×12 foot bedroom using air stored within the packed module. What is so inspiring about the launch of the BEAM is that it could one day replace the ISS altogether. The inflatable segments can be connected together to make larger and larger habitats. If it’s performance is promising, it could mean a future where space hotels on the moon are possible or even full-fledged factories in orbit! There is just so much more room for activities! It’s making my head spin…
I approached this Open Mind a little differently from my latest round of posts. Instead of developing ideas and solutions over the course of a month, I gave myself a “pop” design challenge. The topic: If you were the lead designer for a new NASA Telescope, what considerations would be most important to you? My goal: Instead of developing the best or most important considerations for this challenge, I would develop the first three considerations that popped into my head.
My first thought dealt with finances. As the project manager, I would need to know how much funding the team has and what it will be used for. To me, the days of dumping money into a project especially for exploration are far and few between. It’s unfortunate but there are companies out there that are reviving the passion for space and underwater exploration; our team included. In order to justify spending money on a new exploration project, the team will absolutely have to design intelligently. By using sustainable materials and avoiding “reinventing the wheel”, the design team can focus on improving technology already available thus potentially saving money.
The second thought to pop up was about the project’s overall life cycle. As a manager, I would need to establish an efficient way to not only start and end the project, but see if the telescope has life after decommission. Can anything off the telescope be used or recycled after it’s no longer needed? There’s more to “design” now than ever since there’s a push to go green in all industries. Anything from control systems to frame material can be inspected and potentially approved for reuse. These parts don’t have to be used for serious missions but can be utilized in testing scenarios or for higher education.
The final thought before I called time revolved around power generation. Fuel supply and consumption are always design concerns for any project but none more than in space/underwater applications. There are particles of various sizes translating across space. If a designer can harness the power of small impacts on the telescope by the particles or generate rotational motion from the moving particles, power can be generated. This power can be used to charge batteries in times of need.
Until next time!
About a week ago, NASA tested the RS-25 rocket engine on the new Space Launch System (SLS), a launch vehicle that will drive the next generation of space shuttle deeper into space than we have been able to go thus far. The video (shown below) has been made available to the public and provides an excellent excuse for the discussion of compressible flow regimes.
In the past, our readers have been exposed to the world of fluid mechanics quite often (whether through aeroacoustics, turbulent vortices, hydrodynamic drag, or various other phenomena), and have even been exposed to the subject of compressible flow briefly, so today I am going to give you a bit of an introduction to the subject of gas dynamics and then I will explain the different flow regimes associated with compressible flow.
Fluid mechanics, as discussed previously on this website, is the study of fluids (liquids, gases, plasmas), their movement, and how they interact with internal and external stimuli (loading/forces, pressure differentials, dissipative effects, heat transfer, etc.). Today, we will only be looking at gas dynamics, which differs from the study of liquids in that, for most purposes, liquids (i.e. water) are assumed to be incompressible. With gases, this is not the case. Due to the greater amount of space between free particles, gases have a much greater ability to be compressed. Owing to this compressibility, the terms “gas dynamics” and “compressible flow” are often used synonymously to refer to the same field of study, as compressibility becomes a vital factor as the speed in a gas flow is increased.
As a result of this compressibility, two important phenomena are uniquely encountered within the field of gas dynamics that play a huge role in high speed gas dynamics, as will be defined shortly. The first of these is the choked flow condition, which finds application in the usage of convergent-divergent nozzles (amongst other things), but which will not be discussed here for simplicity. The second of these is the formation of shock waves. Shock waves are essentially pressure waves that have coalesced together to form a “Mach wave”, which represents a discontinuity in the flow field….right, so what in the world does that mean? If an object were to be stationary in the air and have pressure waves emanating from it, they would propagate out in all directions at the same speed (the speed of sound) and form concentric circles about the object. However, as the object begins moving (within subsonic flow), the pressure waves become sent out at different times; in essence, the object sends out a pressure wave, then moves forward and sends out another, and so on (although, this happens basically continually).
As the object’s speeds increase, the center points of these waves get further apart, and thus the waves become compressed in the direction of motion, and expanded in the opposite direction. Eventually, if the object continues moving faster, the object will be moving at the speed of sound, meaning that the object will be travelling at the same speed as the pressure waves are being sent out…in essence, the object has matched or caught up with the pressure waves that it is sending out, and so when the object sends out more pressure waves, they can no longer propagate forward from the object, but rather travel at the same speed, while the portions of the waves traveling backwards are now being left in the dust…figuratively speaking. The waves that are being emenated from the object all at the speed of sound are now really close together and essentially stack up and coalesce into one solid pressure wave that is termed the shock wave. This shock wave can be heard as a “sonic boom” due to the discontinuity or abrupt change in pressure across the shock wave (forward of the wave, the flow is moving at the speed of sound and very low pressure, behind the wave, the flow is moving slower and at a higher pressure). As the object speeds up even further, the object is now starting to outpace the pressure waves all together in what is called supersonic flow, so that the object is leading the waves, which begin to form a mach cone around the object; inside of this mach cone is referred to as the zone of action, while outside of the cone is referred to as the zone of silence. If the object moves even faster, it will eventually get to a speed so high (that of hypersonic flow), that the shock cone will tightly hug the skin of the object so that the distance is so small between the object and the shock wave, that the air gap (the shock layer) begins to heat up due to viscous effects and the aerodynamic heating effect, leading to what we term “high-temperature chemically reacting flow”; the flow is so hot that the gas begins to dissociate or ionize!
So at what speeds does this all occur? To find this out, we define the Mach Number (a.k.a. M or Ma) as the ratio of the object’s speed to the local speed of sound; to understand this, a value of 0.5 would mean that the object is moving at half of the local speed of sound, 1.0 would mean the object is moving at the local speed of sound, and 2.0 would mean the object is moving twice as fast as the local speed of sound.
Up to a value of Ma 0.3, the flow is described as incompressible and thus is analyzed similarly to other incompressible fluid dynamics such as most liquid flow. An example of incompressible flow would be what the baseball encounters when you play catch with a friend.
Once the object hits Ma 0.3, the flow is considered compressible and subsonic in that the object is still moving slower than its pressure waves. An example of subsonic flow would be the flow around many .38 Special bullets.
Once the object reaches about Ma 0.8, transitional instabilities begin to set in and persist to about Ma 1.2; this regime is termed the transonic flow regime and can be seen in basically any application wherein an object is accelerating to supersonic speeds, as the object must pass through the transonic regime to reach the supersonic regime.
Above Ma 1.2, the shock waves have generally been established in full and the vehicle can be said to be in the supersonic flow regime. Applications include supersonic jet engines, such as those found in many military aircraft and supersonic ammunition. More photos will be included here since supersonic flow is the meat of this post.
Lastly, above Ma 5, the aerodynamic heating effect comes into play and the flow enters the hypersonic regime. Applications are hard to come by as this is a subject of a great deal of current research within the fields of mechanical and aerospace engineering (more specifically fluid dynamics); however, one instance of this kind of flow that nearly everyone is familiar with is that of the space shuttle, especially during what is termed re-entry. In fact any re-entry vehicle will experience hypersonic flow, and very likely “hyper-velocity flow” which is essentially an upper range of hypersonic flow speeds.
Barry Wilmore, International Space Station (ISS) Commander, recently needed a wrench that they didn’t have at hand on-board the ISS…so NASA emailed him one. For the first time ever, an object has been designed on Earth and manufactured in space. In earlier years if a situation arose similar to this then the people on the ISS would have to wait for the next resupply mission which could take months! “Made in Space”, a California company designed a micro gravity printer that sits aboard the ISS. Now astronauts can simply print the desired tool they need.
Now whenever something is needed on the ISS, they can now send the requirements to Made in Space, who then mocks up the part in CAD software before sending the data back to be printed in space. However, this is not the first 3D printed part in space, back in November the printer printed a spare part for itself. This means that they can take less tools with them when they travel to the ISS. 3D printing filament is much lighter than tools! In total, 21 objects have been 3D printed in space, all of which have been brought back to Earth for examination and testing. This can only help to improve the printing process in micro gravity. Now only imagine if we can 3D print a spacecraft…Hey…..It could happen!
Space travel has fascinated so many of us since Kennedy promised we’d get a man on the moon. Scientists and engineers worked tirelessly to introduce humans to the rest of the universe and society has benefited greatly from their work. Space travel investment created many things from freeze dried ice cream and Tang to new, more accurate methods for heat transfer calculations. One of the huge improvements was the study of supersonic flow and the convergent-divergent nozzle. This nozzle has made space flight, supersonic jets and all kinds high speed transportation possible. It operates using some pretty interesting ideas.
Most of us are only familiar with nozzles as they apply to garden hoses or shower heads, but some of the same basic principles apply to these new supersonic devices. A converging nozzle increases the speed of the flow, like when you cover part of the head of the hose to spray the water farther. A diverging nozzle is a little less common but it reduces the speed of the flow, like when you adjust your shower head so it’s not blasting you. A convergent-divergent nozzle combines those two back to back and produces velocities greater than the speed of sound. If you’re thinking, “Wait, if a converging nozzle speeds up the flow and a diverging nozzle slows down the flow wouldn’t they just cancel each other out?” you’re pretty on top of your game. This is where compressibility effects come into play. Most of the nozzles we’re familiar with use water, an incompressible fluid, while these nozzles use gasses which are compressible. Imagine you’re coming back from a trip up in the mountains and you have a totally full water bottle and an empty one. The change in altitude will compress the air in the empty bottle, leaving it crumpled while the full water bottle will remain essentially the same.
Air can usually be assumed to act like an incompressible fluid for low speed, like figuring out how strong of winds will take down a billboard or how fast a fan can move air. When air speeds start to reach the speed of sound pretty neat things start happening but first we need to look a bit at what sound is. Sound waves are pressure waves that pass through air very fast, the important thing here is that they’re waves of high pressure. Now lets get back to the nozzle, our first section is a converging nozzle, this speeds up the flow. Lets say that the air is coming in really fast, like almost speed of sound fast, then as it passes through the nozzle it reaches the speed of sound. This means that any of those sound pressure waves trying to move back through the air will be caught in the throat of the nozzle. Kind of like when a person is walking towards the back of a subway train just as it’s leaving the station. They are moving back, but the train is moving forward, so a person standing in the station would see the person in the train as stationary. Also the air is moving so fast that not all of it can get through the throat as fast as it would like so it starts pushing and shoving like a bunch of college kids trying to get free food. This makes the throat of the nozzle a very high pressure region, so high pressure that the flow keeps accelerating through the diverging portion of the nozzle, where incompressible flows would start slowing down. The pressure of the air forces it out like gas out of a shaken soda bottle.
This simple design requires a deep understanding of the world we live in, and it provides the foundation for almost everything that moves at or faster than the speed of sound.
Nothing is as sleek or cool as the color black on anything. Don’t agree? Ferrari’s are most popular in red but have you ever seen a black F40? AMAZING. The color black is associated with power, fear, and elegance but can also mean mystery. Created recently, a new ultra-dark material coating has given us a new level of black void of perspective and depth. Some have said it’s like looking into a black hole. Take a look for yourself:
The material is called Vantablack and it possesses the ability to absorb 99.965% of all incident light. In other words, light (photons) is allowed to enter the material, bounce around, and become trapped with only 0.035% ever leaving the material. With this low percentage of reflection, our eyes are unable to see the material coating, just the space around it. As you can see from the pictures, there is no detail or physical characteristics where the coating is applied.
Surrey NanoSystems, the creator of Vantablack, is very secretive about how this material is made; however, how it works is something we can figure out. Vanta in Vantablack stands for “vertically aligned carbon nanotube arrays”. Carbon nanotubes are known to be very absorbent across a wide variety of radiation including UV light, infrared radiation, and microwaves. These tiny vertical tubes are then densely packed on an aluminum substrate (aluminum foil) in a very controlled environment. This results in a material so absorbent that almost no form of radiation is allowed to escape.
As you may have already figured, Vantablack is only available for the defense and space sectors right now but its uses are endless. Seeing nothing but black void can be great for stealth applications in aircraft, ships, and especially in Team UV’s underwater vehicle. It can also be used in optics for telescopes and imaging. Most imaging systems, especially those used in space, are calibrated against the blackest available colors so it’s obvious Vantablack could lead to even more amazing discoveries.
If you would like more information about Vantablack, Extreme Tech’s article has a link to a technical article!
The galaxy is a wonderful and mysterious thing isn’t it? The only way we have been able to provide answers and/or theories is through pictures granted by the machines we have created. For example, NASA’s Hubble Space Telescope has played a huge role in providing pictures to scientists to conjure answers about our galaxies. However, our answers are only as good as the pictures they provide. If I were to design a telescope for the same use as NASA’s Hubble Telescope here are a few components I would want to do research in.
Research in electrical engineering components is a huge priority in this situation. Since there are a wide variety of electrical components in a space telescope (we have to receive the picture somehow right?) more research in this is needed. There’s dust and gas everywhere in space which could cover the lens and give a bad picture. A Near Infrared Camera & Multi-Object Spectrometer (NICMOS) allows the telescope to observe infrared light, with wavelengths between 0.8 and 2.4 micrometers, providing imaging and slitless spectrophotometric capabilities.
Another major component would be a Space Telescope Imaging Spectrograph (STIS). In space, color has A LOT of information (wavelengths help determine distance, amount of various elements present, etc.). The STIS separates the incoming colors of light to aid in the reading of these pictures. Improvements lead to clearer/informative/breakthrough pictures to help provide a better understanding of space.
Since I’m a mechanical engineering major I have to add something that is relative to my field of study of course! I would definitely look into the engine. Since we can only store a certain amount of fuel in the space telescope it keeps us from going on distant missions. I would look into a device that uses no fuel and provides movement by means of transferring momentum. Since space is considered a vacuum there would be no drag (unless you hit an asteroid then drag is the least of your worries) so you could travel far distances without using up any fuel. With this device we could travel even farther into space and take pictures deeper than we could imagine!
Prompt: Highly interdisciplinary engineering teams are put to work in the design of space telescopes and many fields of engineering must be considered, including (but not limited to): classical mechanics, fluid mechanics, materials science/engineering, heat transfer, electromechanical systems, etc. If you were the head engineer for the design team of the next NASA space telescope, what would be the top 3 design areas/systems that you would choose to put the
greatest focus into developing/improving and why. Remember, there are financial, manufacturing, practical, and theoretical limits to be considered; hence you can never really design the perfect system, some sacrifices must be made, and perhaps the systems you would like to focus on might be impractical to target.
1. Vibration Control: Vibrations can cause the image to blur; however, this could be controlled through material selection and strategic placement of hardpoints along the mirror backing in order to manipulate the vibration modes, node locations, and wave interference, resulting in less vibration. Viscous dampers could also be used to damp out vibration introduced by power supply, boosters, mirror actuators, etc.
2. Thermal Control: Thermal strain within focal optics can cause significant blurring; this can be accounted for with cryocoolers tied to the optics through thermal straps. The cryocoolers use thermodynamic cycles to cool components to cryogenic temperatures, pulling heat from the optics, through the thermal straps, and eventually sinking it out to heat dissipation controls. Current cryocoolers can maintain temperatures down to about 3K which approaches a limit, thus future research could focus on more efficient cryocoolers (rather than lower temperatures) to allow more cryocoolers or other thermal controls for the same power needs.
3. Materials Science: Generally, the more mirrors, the more image blur with respect to telescopes, thus most research efforts focus on use of monocrystalline materials, which are about as optimal as they can be currently without a major revolution in materials forming/manufacturing techniques. Research could then be conducted with respect to improving control in material forming/processing to better tailor mechanical properties (i.e. rigidity) more precisely.