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  • The Bremen Drop Tower is a 140 meter high tower, containing a 120 meter high vacuum

  • chamber which we are using to drop experiments under conditions of nearly perfect weightlessness.

  • The tower consists of the drop shaft, deceleration chamber, a lot of vacuum pumps, and a catapult

  • system which allows us to shoot the experiments from the bottom of the tower to the tip, and

  • then falling back again, doubling the microgravity time to nearly 10 seconds, which is very unique.

  • Scientists from all over the world, in fields from astrophysics to material science to biology, come to this

  • tower to experiment with near zero gravityBecause without the effect of gravity, flames can

  • turn into spheres, strange states of matter appear, and things can just get really interesting.

  • The Bremen Drop Tower was developed and built 30 years agoProfessor Hans Rath, the founder

  • of ZARM and Manfred Fuchs had the idea, and saw the future of Bremen in space sciences

  • and industries. To build a lab that can consistently recreate the conditions of weightlessness,

  • ZARM engineers have to eliminate the effect of gravityGravity is a fundamental force

  • which is acting on all kinds of matterGravity cannot be eliminated but the effect can be

  • eliminated by dropping experiments in free fallAnd freely means, without any external

  • force acting on the experiment while droppingWe are using a vacuum chamber to avoid air resistance

  • during the freefall. And a capsule that can reach velocities up to 165 kilometers per

  • hourMicro in microgravity means that the quality that we are achieving is 1 millionth

  • of Earth's gravity. Everyone can experience microgravity by simply jumping off of somethingAs

  • long as the velocity is small and the air resistance is small, the quality of weightlessness

  • is quite high.

  • Drop Towers have several advantages compared to other microgravity facilitiesOther

  • facilities might be sounding rockets, satellites, space stations, and also parabola flight on

  • planesThe big advantage of drop towers is the accessibilityAnd the repeatability.

  • If one experiment fails, you just try again. On other platforms, this normally is far too

  • expensiveThe tower runs roughly 250 days a year, with up to 3 drops per dayDepending

  • on the experiment, scientists can choose between two different flight campaignsFirst is

  • drop mode, a straight free fall for 4.7 seconds of microgravityHere we are at the tip of

  • the tower in 120 meters heightWhile the experiment is still hanging every motion of

  • the drop tube is leading to a rotational motion of the drop capsule, which again would lead

  • to centrifugal forces during flight time, which you want to avoidSo if you watch

  • closelyWhat you can see here is the effect of mechanical decoupling. The outer structure

  • is moving, but the inner structure of the vacuum chamber is almost stillThe mechanical

  • decoupling of the drop tube allows us to drop experiments even as high wind loads as we have today.

  • The second drop style at the tower utilizes a special catapult system. We are

  • just entering the catapult cellar, 12 meters below the vacuum chamberThe catapult mainly

  • consists of the tube and the piston, the pressure tanks and the hydraulics below. The great

  • advantage is we can double the microgravity time to nearly ten seconds.

  • Without the catapult, a normal drop tower would have to be 500 meters high to

  • achieve the same timeBefore each catapult flight, the experiment capsule is lowered

  • to this point. Here it is standing for a while, and then when shot. These six valves are opened

  • in zero point two seconds and a several hundred liters of oil are rushing through these tubesIt

  • is accelerated with 30 gs, 30 times Earth's gravity to fly it's vertical parabolaAnd

  • believe or not... The whole catapult system is not standing on the ground but hanging

  • on the ceiling. This was necessary to be able to fine adjust the catapult to optimize the

  • flight path of the drop capsule.

  • Experiments range from fundamental physics like quantum

  • mechanics, up to more applied sciences like fire safety devices on space stationsToday

  • we have a very interesting experiment in our drop tube. I'm working now in granular

  • metasciences. And, my position is a researcher at the German center for aerospace research

  • in Cologne. We would like to develop new measurement methods to analyze sand remotely on moon or

  • asteroids. Because we cannot just take a sample, bring it here and investigate itRight now,

  • we are refurbishing the experiment. We circulate water through a sample and measure light scattering

  • propertiesLight scattering is exactly what it sounds like; shining a light on a sample

  • and measuring how fast it fluctuates to reveal a material's inner structureDr. Born

  • and his team can leverage this technique to reveal the dynamic motion of particles on

  • planetary surfaces one dayBut to get there, they have to start with something a bit simpler,

  • like waterThis tower is for us the only place on earth where air bubbles and sand

  • particles move in the same way because they're not affected by gravity. We had the last days

  • some problem with the experiment routines we checked until late night and it worked

  • properly, so I think we have a good chance for a good day for good experiments.

  • The experiment capsule has a diameter of 80 centimeters and is between 1.5 and 2.5 meters long. At

  • the bottom we have a battery pack and service module which is a computer to automize the

  • experiment and to log the dataThe possibilities can range from simple temperature or pressure

  • sensors, up to high speed cameras with up to 1,000 frames per second. And the rest of

  • the volume and space is left for the experimentWhat you can see from here is the piston the big

  • black piece of carbon fiberThe experiment is placed on top of the piston, standing on

  • just this small space.

  • Once the experiment capsule is installed, pumps switch on to suck

  • the air out and create a vacuumThese are our vacuum pumps. We're just starting to

  • evacuate our drop tube. This will take about 90 minutes before we can drop the experiment

  • or shoot the catapult.

  • We want to create scattering from spherical air bubbles and

  • today we hope to see for the first time that they really form perfect spheres in microgravity.

  • We are ready to fly, so I will ask Lisa now to set up everything in action.

  • So we saw in the

  • live video from our sample cell that we had air bubbles in the cell and they really stopped

  • flowingSuch that you have no buoyancy anymore basically they just stop and you can have

  • a look at them in microgravity. And this is what we were actually aiming for so it worked,

  • and yeah, we are very excited about thatIf we have a working set-up, we can change some

  • parametersOn different planets, you have different gravity intensities. If we are able

  • to show how things work in microgravity, we might draw conclusions to different gravity

  • regimes at some point. If you want to investigate the soil on Mars you have to have a method

  • that can remotely investigate packing density or flow behaviorAll the rovers we sent

  • to space so far they went to a so-called stationary operation mode because they just got stuck

  • in sand. So it would be really great to have a sensor in front of the rover which measures

  • the extent of the sand starting to flow. And then we can say, stop, no we cannot drive

  • on the sand, we need to drive somewhere elseWe start with something simple and then we successively

  • increase complexity and see if we can take the theory along.

  • After the flight, the capsule entered the deceleration container here and then we reflooded the drop

  • tube for about 30 minutes, fished for the experiment, and now we are taking it out againEven

  • though the deceleration container is 8 meters in height, it takes approximately 3 meters

  • to decelerate the capsule from 140 kilometers per hour to 0. The cone shape of the capsule

  • limits the deceleration to up to 40 G to shield the experiments from too hard accelerationsAnd

  • also to help break the capsule's fall. The deceleration is achieved using tiny polystyrene

  • balls. The noise that you are hearing is the recycling of our polystyrene balls that were

  • compacted due to the deceleration of the experiment. We are sucking the polystyrene balls out at

  • the bottom and lifting it up to the top again and throw them in again.

  • Now the experiment

  • is opened and the outer shell is removed which remains in the drop tube, and the experiment

  • is handed over to the scientists to prepare the next flight.

  • The existing Bremen drop

  • tower is limited in repetition, mainly by the time that it takes to evacuate this 1,700

  • cubic meters of air out of the drop shaft. We've been asking scientists what they need and

  • what they would want for future drop towers. And they've said 100x more experiments per day.

  • What I am standing on is our new Gravitower Bremen, which is actually under construction.

  • The idea of this new kind of drop tower is that we avoid the vacuum chamber by putting a slider

  • around the experiment, which allows us to repeat experiments all day longWe hope

  • to take it in to normal operation at the end of this year. Then it is open to scientists from

  • all over the worldGiving scientists an even more efficient portal to microgravity will create new

  • opportunities to test ambitious space hardware and speed up the pace of scientific discovery,

  • one drop at a time.

The Bremen Drop Tower is a 140 meter high tower, containing a 120 meter high vacuum

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The Zero Gravity Tower Preparing Us For Future Mars Missions

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    Summer posted on 2020/08/18
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