The Systems Engineer Has Two Critical Tasks

Systems

The systems engineer has two critical tasks. The first is to model the layout of the HAB and prove that all of the components will fit neatly. The second is to calculate the center of mass, which is needed for trajectory reasons. Lastly, the layout of the HAB components will then be adjusted to better meet the needs for controlled flight.

Most of the data for the components has been provided from the other members of project. Some has also been taken from Project PERForM. The remaining pieces have been roughly estimated using engineering judgment. Table A1 in the Appendix shows a detailed listing and description of the components that have been modeled.

The tool used for this analysis is a Matlab program named CGMOI. To use CGMOI, enter the data for each component: mass, dimensions, and positions of center of gravity. This is the same data from Table A1. The program will then give output of the system’s total mass and location of its center of gravity. CGMOI will also produce a three dimensional model of the system. The following figures are the outputs of the CGMOI code.

Figure 1: HAB Level 3

Figure 2: HAB Level 2

Figure 3: HAB Level 1

Figure 4: HAB Garage Level

Figure 5: HAB Hemisphere Level

CGMOI gives a mass value of 34,174 kg, and a center of gravity of (-0.5, 0.1, 4.9)m. These are not the final values. They are merely a step towards the final values. Note that the last unit vector points in the vertical direction. And the other two are in the plane of the base. The origin is at the center of the base.

The next step is to include several components which were not modeled in CGMOI. These components were not included due to their large cumbersome size. The components included here are the structure, TPS, and the pressurized air inside the HAB. Another spreadsheet was made to calculate the new center of gravity. This spreadsheet is shown in Table 1. Note the equation for finding center of gravity:

Roc = (1/m) * SUM(mi * Ropi)

CG Location (m)
Mass (kg) / X / Y / Z
CGMOI / 34174 / -0.5 / 0.1 / 4.9
Structure / 14500 / 0 / 0 / 3.4171
TPS - Hemisphere / 3700 / 0 / 0 / 12.44
TPS - Cylinder / 1050 / 0 / 0 / 5
Air / 941 / 0 / 0 / 8.25
System / 54365 / -0.3143 / 0.062860296 / 5.077565

Table 1: Final Calculation of System Mass and Center of Gravity.

Therefore, this test case has a mass of 54,365 kg and a center of gravity at (0.3143, 0.0629, 5.0776)m. This

center of gravity will need to be moved in time. The obvious way to move the center of gravity is to move

individual components to new coordinates. However, there is another way that may be simpler. This

method is to rotate an entire floor to change the X or Y coordinate. It is also possible to change the level of

some of the floors, which would change the Z coordinate.