Experiment Acceptance Review (EAR) is coming up soon, more specifically, it is on this Thursday. The preparation about the project is ongoing. I wish I could show you some development on the flight dynamics. Unfortunately, I am in a trouble adding the drag torque into the dynamic model of 6 degree of freedom. Sorry for this. The look angle and the azimuth angle looked strange, very different from the previous one when the drag torque was not considered. There were so many parameters that I had no idea what lead to this strange result. According to our supervisors, in order to check all the parameters, we should start with a simple case. Therefore, I started with a very simple case, the FFU falls down, only drag in vertical direction, no wind, which is helpful to figure out this problem. I feel this is not an easy task, which will take some time. I hope I can get a reasonable result soon.
Today, let me digress for a while with regards to the post. But as a matter of fact, what I want to present is a little related to ISAAC, as well as flight dynamics.So what I am going to talk about? Er, it is computer simulation.
As you might know, in order to study the science, and get to know the real world around us, we commonly need to do some experiments. When it comes to an experiment, you may well think of scientists in white coats working away in a laboratory. Well, in fact, computer simulation is also belong to one type of experiments, which sometimes is called “computer experiment”.
Here, a model is implemented on a computer leading to a dynamic demonstration. Further
interventions can then be programmed to explore how they affect the scenario. In some sense, this is clearly more about modelling than experimenting, because the control and intervention is performed on a representation, not the “real stuff” used in field or laboratory experiments. Anyway, to run an experiment on a computer is thus similar to experiment with a laboratory animal: both are used to experiment, in order to learn about a substantially different target.
In terms of the definition of an experiment, which is a controlled observation in which the observer manipulates the variables that are believed to influence the outcome, therefore, computer simulation is a kind of experiments.
Up to last post, we had considered cases with drag with wind and not, and varying ejection angles. And all the simulations were based on the symmetry of FFUs. However, the more actual situation is that I22 does not equal I11. Therefore, in the past days, we took into account the varying I22/I11 ratio.
Fig.16 illustrates the changes of look angles with I22/I11 from 0.5 to 1.8. As I22/I11 increases, both the absolute values of maximum and minimum of look angles gradually grow till the ratio of 1.6, afterwards, these values rise fast. The changes are not larger than 1 degree, compared the maximum and minimum value of look angles Fig.16 with the ones in Fig.15 until I22/I11=1.6. Neverthless, when I22/I11 reaches 1.8, the maximum and minimum of look angles increases several degrees. As a consequence, over the interval of I22/I11 between 0.5 and 1.8, the maximum and minimum of look anlges are 5.27 deg and -10.76 deg, respectively, which are obtained when I22/I11 is 1.8.
Fig.a shows that look angles vary as ejection angles change when I22/I11 is held.
In Fig.a, star and circle represent the maximum and minimum of look angles, respectively. Red and black stand for look angles when I22/I11 equals 1.8 and 0.5, respectively. The maxima of look angles grow slowly, in contrast, the minima of look angles reduce gradually, as ejection angles become larger.
Okay, right now we have known the situation with asymmetrical geometry. What shall we do next? Next, we are going to consider the case when there is drag torque applied on FFUs. Let us wait for the new results.
For Isaac-Rx to track Isaac-Tx, we need to know the orientation from Tx to Rx. Thus we define look angles and azimuth angles to describe the orientation.
Recently, we have made some progress in look angles and azimuth angles. We took into account drags, winds and ejection angles in simulations, to understand the effect of winds and ejection angles on look angles.
All the graphs were obtained on the base of adding drags, but one set was based on without wind, while the other one was based on with wind, and at the same time, the ejection angles changed.
From these figures, we can see that winds affect the look angles a little when the ejection angles are same. However, the ejection angles have a large effect on the look angles. Above is our conclusion.
Today, the Integration Progress Review (IPR) of ISAAC is proceeding. A guy comes to examine the status of our project. I gave my presentation in the morning. It was the first time for me to give a kind of formal presentation to someone outside the team. I was a little nervous before the presentation.
To do it well, I had been preparing it from yesterday to this morning. I went through the previous documents. Unfortunately, I found there was something wrong with simulations. So I redid some simulations and made a powerpoint. At first, I thought there were not much stuff to talk about. However, when I read these documents, I realized in fact I had done a lot of simulations on the flight dynamics. These simulations were started with the simple case, for example, no drag and perpendicular ejection when computing look angles and azimuth angles. But later, drag and ejection angles were gradually added in it so that the contents got more and more rich and complete. I think this is the way to start something. For this preparation, I stayed up last night. I hope I could have an early sleep tonight.
The end of July is coming. With my laborious colleagues, we have finished a lot on CDR so far. For most of Isaac team members, the summer holiday is about to end; and for me, it is over and also a start point of a new academic year. After a long and nice vacation, I feel relaxed and full of energy. At this moment, I would like to summarize my previous work and plan the next task.
As for my part, the flight dynamics, we got possible flight trajectories and landing zones through simulations as well as the attitude trajectories. And the next, I will continue to the attitude analysis in a more complicated and actual situation, considering the balance of FFUs.
Let’s go on the way again!
June, is a beautiful period in Stockholm. Many students have left their schools for travel or and fun, or for intership and work. However, our Isaac team, are still continuing to work on this project. The Critical Design Review (CDR) is coming up, we have a lot of work to do. Although we have submitted the SED v2.0, we still need to do some modification and iteration on the mechanical and electrical design. We need to prepare the powerpoints for the CDR presentation. CDR requires most of key design, which covers a lot of technical knowledge and problems. So we have to prepare for the questions and comments from experts on these techniques. OK, let’s go on.