Mec

Mechanical Structure discussions to go here

Inspection of PLUME skeletized structure

## Approximate Budgets following the MRR:

Subsystem Mass (g) Power (W) Volume (mm x mm x mm) Cost (£)
PAY 160 -0.6 continuous PMT's = 2 x (50.0 +/-0.5 x 50.0 +/-0.5 x at least 12-16) 1600 approx
CAM 20 -0.1 20 x 20 x15 approx ?
PSU (incldng BATT) 164.19 +1,4 continuous 9216 ?
COMS 115 -0.33/1.48 ? ?
Antenna 50 n/a 50 x 50 x 10 stored (2 ariels of 90 x 90 x 5 deployed) 350 - 550
OBDH 74 0.008 96 x 90 x 16.5 ?
ADCS 6 -0.13/0.55 Board: 50 x 50 x 10 ?
BUS 170 n/a 100 x 100 x 100 ?
Total 858.19 0.24/-0.83 106 x 106 x 106 stored ?

Table 1: Up to date budgets for the mass, power, volume and cost of each subsystem

These figures do not include margins.

They are of a square ring design and the figure in the table is their outer dimensions. They have an inner diameter of 90mm, so the volume was calculated by subtracting a cuboid of 90mm x 90mm x 5mm from a cuboid of 94mm x 94mm x 5mm. (This gives a value of 3680mm3)

## Breakdown of PSU mass:

Component Mass (g)
Solar Panels 10.56
Battery 44
Power Control Board 50

Table 2: Mass breakdown of PSU subsystem

The estimates for masses for the battery and solar panels are based on technical specification. The control board is an estimate based on Clydesat.

## Structure:

cubesatkit users manual

On the link above (user manual) there's a 57 page document from pumpkin inc all about the cubesat kit. Basically the structure is divided up into slots, roughly either 4 or 5. The bootom slot (slot 0) takes the flight module, that takes up the bottom 25mm of the cubesat.

## Carbon fibres?

It has been suggested that, for reduced mass and improved fittings within the cubesat, Carbon fibres could be used in place of the Aluminium frame. Or maybe a half Aluminium half Carbon fibre combination.

I looked at the flight regulations from the P-POD bus and I'm not sure this is faesable. One of the specifications our cubesat has to meet is that, if made from an alternative material, it has to have a Coefficient of Thermal Expansion (CTE) similar to that of Al 7075-T73. The value for this I found, from Aerospace Metals, was 23.6 x 10-6m.m-1.oC-1. After looking for similar values for Carbon fibre, I found several qouting a CTE of about 0.54 x 10-6m.m-1.oC-1. The other consideration is that Carbon fibre is not isotropic in its thermal properties, so this would vary greatly upon direction. Without finding a really different Carbon fibre with a CTE of about 23-25, I think it's unlikely we can get approval from the P-POD technicians.

Carbon fibres are not a viable option for the BUS structure

## Centre of Mass:

The centre of mass of the overall structure must lie within 2cm of the structures geometric centre.

## Thermal Modeling

This simplified model has been created using an excell spreadsheet. Currently using an orbital height of 1000km the maximum dayside temperature is 315K and the minimum nightside temperature is 228K. For details look at the Thermal Modeling Paper and the Excel Worksheet.