The Space Shuttle Had A Famous Double Sonic Boom When Passing Overhead During Re-entry. This Schlieren

Despite their ubiquity and importance, we know surprisingly little about how clouds form. The broad strokes of the process are known, but the details remain somewhat fuzzy. One challenge is understanding how nucleation – the formation of droplets that become clouds or rain – works. A recent laboratory experiment in an analog cloud chamber suggests that falling rain drops may help spawn more rain drops.

The experiment takes place in a chamber filled with sulfur hexafluoride and helium. The former acts like water in our atmosphere, appearing in both liquid and vapor forms, while the latter takes the place of dry components of our atmosphere, like nitrogen. The bottom of the chamber is heated, forming a liquid layer of sulfur hexafluoride, seen at the bottom of the animation above. The top of the chamber is cooled, encouraging sulfur hexafluoride vapor to condense and form droplets that fall like rain. A top view of the same apparatus during a different experiment is shown in this previous post. 

When droplets fall through the chamber, their wakes mix cold vapor from near the drop with warmer, ambient vapor. This changes the temperature and saturation conditions nearby and kicks off the formation of microdroplets. These are the cloud of tiny black dots seen above. Under the right conditions, these microdroplets grow swiftly as more vapor condenses onto them. In time, they grow heavy enough to fall as rain drops of their own. (Image credits: P. Prabhakaran et al.; via APS Physics; submitted by Kam-Yung Soh)

that’s the Captain’s prerogative 

#work

#work

Earth’s rotation and Space shuttle launches

Last week we were talking about wind patterns and how they affect flight time. But it is also worth mentioning that Space shuttles are launched almost at all times from West to East to take advantage of the earth’s rotation

How does earth’s rotation affect shuttles ?

Earth is a spherical body rotating with some angular velocity. And as a result of this, the equator is rotating at a higher velocity than the poles. By launching a space shuttle from the equator you are getting a ‘speed boost’.  

This means that if a shuttle is launched from the pole, it has to accelerate from 0 to 17000mph to reach orbital velocity.

But if a shuttle is launched from the equator, it only needs to accelerate from 1025 to 17000mph. (that 1025mph initial velocity is given by the earth free of charge)

This saves valuable amount of fuel required for propulsion

Polar Orbits

Not all rockets are launched from the west to east and the direction is determined by the purpose of its payload.

The satellites that are used for mapping for instance follow a Polar Orbit i.e they move from north to south or vice versa and therefore during launch they cannot take advantage of the earth’s rotation.

Florida or California

Another characteristic of launching satellites is that the launching stations are generally located near the coast just in case of failure of the launch, the satellite falls in an uninhabited area.

NASA primarily uses Kennedy Space Center, Florida for east-west launches and Vandenberg Base California for polar orbits for the very same reason. ***

Rocket science is just truly breathtaking.

* How fast are YOU spinning on Earth’s axis right now?

** Also check out about Retrograde motion

*** This statement holds true for most launches.

Reinventing the Wheel

Planning a trip to the Moon? Mars? You’re going to need good tires…

Exploration requires mobility. And whether you’re on Earth or as far away as the Moon or Mars, you need good tires to get your vehicle from one place to another. Our decades-long work developing tires for space exploration has led to new game-changing designs and materials. Yes, we’re reinventing the wheel—here’s why.

Wheels on the Moon

Early tire designs were focused on moving hardware and astronauts across the lunar surface. The last NASA vehicle to visit the Moon was the Lunar Roving Vehicle during our Apollo missions. The vehicle used four large flexible wire mesh wheels with stiff inner frames. We used these Apollo era tires as the inspiration for new designs using newer materials and technology to better function on a lunar surface.

Up springs a new idea

During the mid-2000s, we worked with industry partner Goodyear to develop the Spring Tire, an airless compliant tire that consists of several hundred coiled steel wires woven into a flexible mesh, giving the tires the ability to support high loads while also conforming to the terrain. The Spring Tire has been proven to generate very good traction and durability in soft sand and on rocks.

Spring Tires for Mars

A little over a year after the Mars Curiosity Rover landed on Mars, engineers began to notice significant wheel damage in 2013 due to the unexpectedly harsh terrain. That’s when engineers began developing new Spring Tire prototypes to determine if they would be a new and better solution for exploration rovers on Mars.

In order for Spring Tires to go the distance on Martian terrain, new materials were required. Enter nickel titanium, a shape memory alloy with amazing capabilities that allow the tire to deform down to the axle and return to its original shape.

These tires can take a lickin’

After building the shape memory alloy tire, Glenn engineers sent it to the Jet Propulsion Laboratory’s Mars Life Test Facility. It performed impressively on the punishing track.

Why reinvent the wheel? It’s worth it.

New, high performing tires would allow lunar and Mars rovers to explore greater regions of the surface than currently possible. They conform to the terrain and do not sink as much as rigid wheels, allowing them to carry heavier payloads for the same given mass and volume. Also, because they absorb energy from impacts at moderate to high speeds, there is potential for use on crewed exploration vehicles which are expected to move at speeds significantly higher than the current Mars rovers.

Airless tires on Earth

Maybe. Recently, engineers and materials scientists have been testing a spinoff tire version that would work on cars and trucks on Earth. Stay tuned as we continue to push the boundaries on traditional concepts for exploring our world and beyond.  

Make sure to follow us on Tumblr for your regular dose of space: http://nasa.tumblr.com.  

Saturn V

The Saturn rocket series’ biggest brother, the culmination of America’s efforts during the Cold War Space Race against the Russians, and the paragon of human spaceflight achievement, The Apollo program’s primary tool was the mighty Saturn V, the pride of American space exploration, and NASA’s poster child. Designed by Wehrner von Braun, the massive rocket took 24 astronauts beyond Earth’s orbit, 12 of which walked on the Moon.

The Saturn V dwarfed every previous rocket fielded by America in the Space Race, remaining to this day the tallest, heaviest, and most powerful rocket ever brought to operational status and still holds records for the heaviest payload launched and largest payload capacity. On the pad, she stood 363 feet (111m) tall, taller than the Statue of Liberty by 58 feet, with a diameter of 33 feet (10m), and weighed 6.5 million pounds fully fueled. Her designed payload capacity was rated at 261,000 pounds (118,000 kg) to Low Earth Orbit and 90,000 pounds (41,000 kg) to the Moon, but in later missions was able to carry about 310,000 pounds (140,000 kg) to LEO and sent up to 107,100 lb (48,600 kg) worth of spacecraft to the Moon.

The total launch vehicle was a 3 stage vehicle: the S-IC first stage, S-II second stage and the S-IVB third stage. The first stage used RP-1 for fuel, while the second and third stages used liquid hydrogen (LH2), with all three using liquid oxygen (LOX) for oxidizer.

First Stage

The first stage of the Saturn V is the lower section of the rocket, producing the most thrust in order to get the vehicle off the pad and up to altitude for the second stage.

The Rocketdyne F-1 engine used to propel the rocket was designed for the U.S. Air Force by Rocketdyne for use on ICBM’s, but was dropped and picked up by NASA for use on their rockets. This engine still is the most powerful single combustion chamber engine ever produced, producing 1,522,000 lbf (6,770 kN) at sea level and 1,746,000 lbf (7,770 kN) in a vacuum. The S-IC has five F-1 engines. Total thrust on the pad, once fully throttled, was well over 7,600,000 lbf, consuming the RP-1 fuel and LOX oxidizer at a jaw-dropping 13 metric tonnes per second.

The launch sequence for the first stage begins at approx. T-minus 8.9 seconds, when the five F-1 engines are ignited to achieve full throttle on t-minus 0.  The center engine ignited first, followed by opposing outboard pairs at 300-millisecond intervals to reduce the structural loads on the rocket. When thrust had been confirmed by the onboard computers, the rocket was “soft-released” in two stages: first, the hold-down arms released the rocket, and second, as the rocket began to accelerate upwards, it was slowed by tapered metal pins pulled through dies for half a second.

It took about 12 seconds for the rocket to clear the tower. During this time, it yawed 1.25 degrees away from the tower to ensure adequate clearance despite adverse winds. (This yaw, although small, can be seen in launch photos taken from the east or west.) At an altitude of 430 feet (130 m) the rocket rolled to the correct flight azimuth and then gradually pitched down until 38 seconds after second stage ignition. This pitch program was set according to the prevailing winds during the launch month. The four outboard engines also tilted toward the outside so that in the event of a premature outboard engine shutdown the remaining engines would thrust through the rocket’s center of gravity. At this point in the launch, forces exerted on the astronauts is about 1.25 g.

At about T+ 1 minute, the rocket has gone supersonic, at which point, shock collars form around the rocket’s second stage separator. At this point, the vehicle is between 3 and 4 nautical miles in altitude.

As the rocket ascends into thinner atmosphere and continues to burn fuel, the rocket becomes lighter, and the engine efficiency increases, accelerating the rocket at a tremendous rate.  At about 80 seconds, the rocket experienced maximum dynamic pressure. Once maximum efficiency of the F-1 engines is achieved, the total thrust peaks at around 9,000,000 lbf. At T+ 135 seconds, astronaut strain has increased to a constant 4 g’s.

At around T+ 168 seconds, the engines cut off as all fuel in the first stage is expended. At this point in flight, the rocket is  at an altitude of about 36 nautical miles (67 km), was downrange about 50 nautical miles (93 km), and was moving about 6,164 miles per hour (2,756 m/s). The first stage separates at a little less than 1 second following engine cutoff to allow for engine trail-off.  Eight small solid fuel separation motors backs the S-IC from the rest of the vehicle, and the first stage continues ballistically to an altitude of about 59 nautical miles (109 km) and then falls in the Atlantic Ocean about 300 nautical miles (560 km) downrange. Contrary to the common misconception, the S-IC stage never leaves Earth’s atmosphere, making it, technically, an aircraft.

Second Stage

The second stage is responsible with propelling the vehicle to orbital altitude and velocity. Already up to speed and altitude, the second stage doesn’t require as much Delta-V to achieve it’s operation.

For the first two unmanned launches, eight solid-fuel ullage motors ignited for four seconds to give positive acceleration to the S-II stage, followed by start of the five Rocketdyne J-2 engines. For the first seven manned Apollo missions only four ullage motors were used on the S-II, and they were eliminated completely for the final four launches. 

About 30 seconds after first stage separation, the interstage ring dropped from the second stage. This was done with an inertially fixed attitude so that the interstage, only 1 meter from the outboard J-2 engines, would fall cleanly without contacting them. Shortly after interstage separation the Launch Escape System was also jettisoned.

About 38 seconds after the second stage ignition the Saturn V switched from a preprogrammed trajectory to a “closed loop” or Iterative Guidance Mode. The Instrument Unit now computed in real time the most fuel-efficient trajectory toward its target orbit. If the Instrument Unit failed, the crew could switch control of the Saturn to the Command Module’s computer, take manual control, or abort the flight.

About 90 seconds before the second stage cutoff, the center engine shut down to reduce longitudinal pogo oscillations (a forward/backward oscillation caused by the unstable combustion of propellant). At around this time, the LOX flow rate decreases, changing the mix ratio of the two propellants, ensuring that there would be as little propellant as possible left in the tanks at the end of second stage flight. This was done at a predetermined Delta-V.

 Five level sensors in the bottom of each S-II propellant tank are armed during S-II flight, allowing any two to trigger S-II cutoff and staging when they were uncovered. One second after the second stage cut off it separates and several seconds later the third stage ignited. Solid fuel retro-rockets mounted on the interstage at the top of the S-II fires to back it away from the S-IVB. The S-II impacts about 2,300 nautical miles (4,200 km) from the launch site.

The S-II would burn for 6 minutes to propel the vehicle to 109 miles (175km) and 15,647 mph, close to orbital velocity.

Third Stage

Now in space, the third stage, the S-IVB’s sole purpose is to prepare and push the Command, Service, and Lunar Modules to the Moon via TLI. 

Unlike the two-plane separation of the S-IC and S-II, the S-II and S-IVB stages separated with a single step. Although it was constructed as part of the third stage, the interstage remained attached to the second stage.

During Apollo 11, a typical lunar mission, the third stage burned for about 2.5 minutes until first cutoff at 11 minutes 40 seconds. At this point it was 1,430 nautical miles (2,650 km)  downrange and in a parking orbit at an altitude of 103.2 nautical miles (191.1 km)  and velocity of 17,432 mph (7,793 m/s). The third stage remained attached to the spacecraft while it orbited the Earth one and a half times while astronauts and mission controllers prepared for translunar injection.

This parking orbit is quite low, and would eventually succumb to aerodynamic drag if maintained, but on lunar missions, this can be gotten away with because the vehicle is not intended to stay in said orbit for long. The S-IVB also continued to thrust at a low level by venting gaseous hydrogen, to keep propellants settled in their tanks and prevent gaseous cavities from forming in propellant feed lines. This venting also maintained safe pressures as liquid hydrogen boiled off in the fuel tank. This venting thrust easily exceeded aerodynamic drag.

On Apollo 11, TLI came at 2 hours and 44 minutes after launch. The S-IVB burned for almost six minutes giving the spacecraft a velocity close to the Earth’s escape velocity of 25,053 mph (11,200 m/s). This gave an energy-efficient transfer to lunar orbit, with the Moon helping to capture the spacecraft with a minimum of CSM fuel consumption.

After the TLI, the Saturn V has fullfilled its purpose of getting the Apollo crew and modules on their way to the Moon. At around 40 minutes after TLI, the Command Service module (the conjoined Command module and Service Module) separate from the LM adapter, turns 180 degrees, and docks with the exposed Lunar Module. After 50 minutes, the 3 modules separate from the spent S-IVC, in a process known as Transposition, docking and extraction. 

Of course, if the S-IVC were to remain on the same course (in other words, if they leave it right there unattended), due to the physics of zero gravity environments, the third stage would present a collision hazard for the Apollo modules. To prevent this, its remaining propellants were vented and the auxiliary propulsion system fired to move it away. Before Apollo 13, the S-IVB was directed to slingshot around the Moon into a solar orbit, but from 13 onward, the S-IVB was directed to actually impact the Moon. The reason for this was for existing probes to register the impacts on their seismic sensors, giving valuable data on the internals and structure of the Moon.

Launch Escape System

The Saturn V carries a frightening amount of potential energy (the Saturn V on the pad, if launch failed and the rocket ruptured and exploded, would have released an energy equivalent to 2 kilotons of TNT, a force shy of the smallest atomic weapons), which luckily was unleashed as planned without incident. However, this being NASA, precautions were made to save the crew in event of a catastrophic failure. 

The LES (Launch Escape System) has been around since the Mercury Program as a way to get the crew capsule away from a potential explosion on the pad or in early launch. The idea is that a small rocket would take the capsule far enough away from the rocket that parachutes could be deployed.

The LES included three wires that ran down the exterior of the launch vehicle. If the signals from any two of the wires were lost, the LES would activate automatically. Alternatively, the Commander could activate the system manually using one of two translation controller handles, which were switched to a special abort mode for launch. When activated, the LES would fire a solid fuel escape rocket, and open a canard system to direct the Command Module away from, and off the path of, a launch vehicle in trouble. The LES would then jettison and the Command Module would land with its parachute recovery system.

If the emergency happened on the launch pad, the LES would lift the Command Module to a sufficient height to allow the recovery parachutes to deploy safely before coming in contact with the ground.

An interesting factoid is how much power the LES possesses; in fact, the LES rocket produces more thrust (147,000 pounds-force (650 kN) sea level thrust) than the Mercury-Redstone rocket (78,000 pounds-force (350 kN)) used to launch Freedom-7 during the Mercury program. 

Skylab 

After budget cuts necessitated mission cancellations and the end of the Apollo program, NASA still had at least one Saturn V rocket intended for Apollo 18/19. Luckily, in 1965, the Apollo Applications Program was established to find a use for the Saturn V rocket following the Apollo program. Much of the research conducted in this program revolved around sending up a space station. This station (now known as Skylab) would be built on the ground from a surplus Saturn IB second stage and launched on the first two live stages of a Saturn V. 

The only significant changes to the Saturn V from the Apollo configurations involved some modification to the S-II to act as the terminal stage for inserting the Skylab payload into Earth orbit, and to vent excess propellant after engine cutoff so the spent stage would not rupture in orbit. The S-II remained in orbit for almost two years, and made an uncontrolled re-entry on January 11, 1975. 

This would be NASA’s only Saturn V launch not associated with the Apollo program, and unfortunately, would prove to be the Saturn V’s last one. There were other concepts for Saturn V’s as launch vehicles, including a space shuttle design, but none of these ever came to fruition. 

Cost

From 1964 until 1973, a total of $6.417 billion ($41.4 billion in 2016) was appropriated for the Saturn V, with the maximum being in 1966 with $1.2 billion ($8.75 billion in 2016). 

Displays and Survivors

There are several displays of Saturn V rockets around the United States, including a few test rockets and unused ones intended for flight. The list below details what and where they are.

Two at the U.S. Space & Rocket Center in Huntsville:

SA-500D is on horizontal display made up of S-IC-D, S-II-F/D and S-IVB-D. These were all test stages not meant for flight. This vehicle was displayed outdoors from 1969 to 2007, was restored, and is now displayed in the Davidson Center for Space Exploration. The second display here is a vertical display (replica) built in 1999 located in an adjacent area.

One at the Johnson Space Center made up of first stage from SA-514, the second stage from SA-515 and the third stage from SA-513 (replaced for flight by the Skylab workshop). With stages arriving between 1977 and 1979, this was displayed in the open until its 2005 restoration when a structure was built around it for protection. This is the only display Saturn consisting entirely of stages intended to be launched.

One at the Kennedy Space Center Visitor Complex, made up of S-IC-T (test stage) and the second and third stages from SA-514. It was displayed outdoors for decades, then in 1996 was enclosed for protection from the elements in the Apollo/Saturn V Center.

The S-IC stage from SA-515 is on display at the Michoud Assembly Facility in New Orleans, Louisiana.

The S-IVB stage from SA-515 was converted for use as a backup for Skylab, and is on display at the National Air and Space Museum in Washington, D.C.

Source: Wikipedia

you tell ‘em, borg lady

1988 Buran Energia pad

What the F*ck is a Wormhole?

Wormholes have been a beloved aspect of dozens of different science fiction novels, TV shows, and movies. If you’ve watched or read anything science fiction, you’ve probably heard of them. They’re typically portrayed as just a door or tunnel, that when stepped through, you simply “arrive” at the other side, often times many thousands of light-years away. Not only do they sound pretty f*cking neat, wormholes actually have a fair amount of mathematical support behind them. 

Ever since wormholes were officially introduced into the scientific community in 1957 by John Wheeler and Charles Misner, scientists have been thoroughly tinkering with their fascinating and also terrifying possibilities. Despite the fact they seem too good to be true, Einstein’s field equations permit a traversable wormhole to actually exist in our universe. The ability to use wormholes would make traveling to otherwise unreachable areas of the universe a real possibility. So, instead of traveling from point A to B in a typical linear fashion—which in terms of space travel usually means many lifetimes—a wormhole is just a shortcut. 

Here’s a nice Wikipedia photo since the description of my bank account is equal to my artistic ability—not so good. It vaguely illustrates how a wormhole connects two points together by manipulating spacetime.

A wormhole is sort of like plugging a Game Genie into the universe. Just plug the Game Genie in, open up the cheat menu, and well, it might cause glitches, but f*ck it—let’s just create a whole separate dimensional plane in which to travel through and call it hyperspace. In all seriousness, this dimensional plane is literally known as hyperspace (all hail sci-fi nerd scientists). Hyperspace is the where the actual “tunnel” of the wormhole exists. Sound like some sci-fi bullshit right? Well, it’s not.

Wormhole problems Around 1985, Caltech professor Kip Thorne, with his graduate student Mike Morris, set out to design a fully traversable wormhole. But they had to iron out a few rather glaring snags preventing theoretical travel through a wormhole. 

A traditional wormhole has two “mouths” that tend to open and close with a flicker. They close with such speed and force that it would be impossible to traverse through without something to “hold the mouths open.” This makes safe traversing somewhat problematic. Without something to prop it open, it would collapse on you with the collective pressure of a neutron star (which, in case you were wondering, is a ridiculously goddamn high amount of pressure— you’d be f*cked into another dimension).

In order to avoid being f*cked into another dimension, they needed something to keep the wormhole open artificially. Thorne conceived a “recipe” to solve this rather glaring problem—negative, or exotic, matter. Negative matter is just normal matter, but in reverse. Normal matter is damn sexy (attracts), and negative matter is ugly as hell (it repels). The repulsive gravitational field generated by negative matter would be enough to keep the “mouth” of both ends of the wormhole open long enough to travel through, or to keep it open indefinitely. Thorne, among other scientists, have speculated that an advanced enough race could develop a method to easily manipulate negative matter as they please—allowing effortless travel through the cosmos.

Fun fact: Thorne worked out much of the scientific details of his wormhole to help Carl Sagan with his novel, Contact.

Time Travel? Thorne (and many many other scientists) believe a wormhole could potentially act as a bridge in time. For the sake of simplicity, I won’t go in to the entire complex nature of this hypothesis. Though the more you delve into it, the trippier it gets. For a small taste, here’s an example from Igor Novikov I simplified: say two clocks, with the same time, are at either end of a wormhole, but one end is within the gravitational field of a neutron star (the pace of time depends on the strength of the gravitational field). Stepping through would essentially send you to the past. You could even see yourself about to enter the wormhole if you waited long enough. So, you could potentially see yourself from a different point in time. F*ck, my brain hurts.  This example just keeps getting more complex depending on the gravitational field, the amount of observers and their locations, and the amount of times you step through.  There are also a vast number of paradoxes that can occur from even a simple example like this one. Trying to shit on times comfy, linear home is a dangerous game to be played, as illustrated in numerous science fiction tales.     I’ll delve deeper into wormholes and other mathematical curiosities which would permit time travel in a future article!

Conclusion For now, unfortunately, wormholes are still just a mathematical curiosity. They have never been directly observed quite yet. But the universe is sort of a clusterf*ck of crazy things happening, so the possibility of a bridge in spacetime existing is no longer just science fiction.

For the sake of brevity I’ve cut out a great deal of additional content about wormholes. Wormholes that can be conjured up from “quantum foam,” wormholes without event horizons, the Ellis-Bronnikovwormhole which functions without exotic matter (they were the first ever to publish a paper on a traversable wormhole), etc.

Like this article? Consider helping me write more by giving Fuck Yeah, Astrophysics $1 a month (that’s about $0.03 a day) on Patreon! A $2-3 tier is also coming that has monthly goodies :) 

Would you like to see a part 2? Think this article was garbage? Think it was great? Think I’m a shill for Thorne, and that the Ellis-Brannikov wormhole is the truly proper wormhole? Let me know in the comments/re-blogs :)

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References: The Future of Spacetime, How To Build a Time Machine, The New Time Travelers. Image Credits, from top to bottom: Corvin Zahn (wormhole illustration), Panzi (Source), Les Bossinas (Advanced spacecraft) All other sources or references used are linked to in the article :)