Hanging By A Thread (Pt. 1)
Hello people! Danai here once again to talk about the next step for our Magnetometer Boom Assembly (MBA) on the road to launch, testing!
Previously we spoke about the design phase and the structural analysis phase of the MBA. After we establish that we are satisfied with those two phases, the next step is to manufacture the testing prototype and start testing. If the results of the testing phase are up to standard, then we manufacture the flight unit and we are ready for launch! Otherwise we evaluate what went wrong, correct it, test again, until we get it right!
On the image below we have a small reminder of our system, the MBA is a 2m long structure composed of three parts, Base, Mid and Tip connected by two sets of tape springs, intended to carry the two magnetometers of the experiment. It is stowed during ascension of the rocket and deploys a short while after the ejection of the Free Falling Unit (FFU).
As mentioned above, before we started with the testing, we manufactured the testing prototype, which you can see below.
Back to testing! The most important part for the MBA is to deploy properly, and to verify that it will, we need to test it. To test the deployment is a challenge, since it’s designed to deploy in microgravity at 80km altitude and the tape springs that provide structural support for the boom, are not stiff enough to make the deployment work down here on Earth. The way to solve this problem is to perform a Gravity Off-Loading test, this way we can simulate weightlessness. Let’s see how it works.
The principle is based on what is called the “Marionette Paradigm”, where the weight of each part is balanced by the other parts. While the boom is stowed we tie three different strings around the Base, Mid and Tip parts of the MBA, and tie the other end of these three strings on a fly-beam (yellow beam) at points A, B and C, see image on the left. Following that, we tie the fly-beam from point G and hang it from the ceiling, allowing the fly-beam to rotate around G. When ready, we cut the string that holds the MBA stowed and it deploys, reaching the second state, see image on the right.
For the test to work we need to meet several conditions between the two states, achieve moment equilibrium around point G, while h remains constant. Meaning that there is no motion in y or z direction, but only in x, this can be achieved by the addition of extension springs ls1, ls2 and ls3, to compensate for the change in distances L1, L2 and L3 between the two states. Another important condition is to minimize the “traveling angles” α, α‘, β, β’, γ, γ’, this can be achieved by increasing h as much as possible. The height of the Gravity Off-Loading system we currently build is 12m.
Taking into consideration the conditions mentioned above, along with other geometric conditions we end up with a system of 32 equations and unknowns that when solved it gives us all the dimensions and parameters we need to build the GOL system. We will perform the test several times while recording and analyzing the results.
We’ll keep you posted when the results are out, we know you are excited as much as we are! For now I bid you farewell! Check out our website: www.b2d2.se, our Facebook page, and our Instagram accounts. Stay healthy!