Antenna how to guide - spacecraft-design-lab-2019/documentation GitHub Wiki

Antenna how-to-guide

Jargon/Parts

A-Boom The structural elements that hold the antenna, going from the stowed to the extended position. In baselined design, the boom and upper conductor are the same components. Baseline part: .06” x .0115” Nitinol superelastic strip 2 x 7”

A-Upper Conductor The upper carrier of signal that does not have connectors to the satellite. In baselined design, the boom provides sufficient conductivity. Baseline part: .06” x .0115” Nitinol superelastic strip 2 x 7”

B-Lower Conductor The portion of the antenna that connects to the satellite circuit board. In the baselined design, the lower conductor is 8mm of copperwire wrapped around the base of the boom, then running underneath the bracket and soldered to the underside of the +Y board. Baseline part: 26 AWG copper wire. 2 x <12”

C-Bracket Holds the antenna components in place. It’s held down with an extended M2 screw attached to the corner post. The bracket is prevented from radial turns by pressing against the solar panel. Baseline part: XT2 Windform bracket. 20mm x 6mm x 8mm https://a360.co/38lvlEn Spacecraft Design Lab/Antennas/Bracket/Baseline Bracket and Glue Guide

D-Bracket Post Holds the antenna bracket and +Y board to the structural arch. Baseline part: 18-8 Stainless Steel Socket Head Screw M2 x 0.4 mm Thread, 10 mm Long Part number: 91292A833

E- Stowage Post Holds the right facing boom when stowed. It’s the same part as the Bracket Post, with a heat set insert as a spacer and (possibly) a rubber hose insulating it. Baseline parts: 18-8 Stainless Steel Socket Head Screw M2 x 0.4 mm Thread, 10 mm Long Part number: 91292A833

F- Burn Wire The burn wire has current passed through it to generate heat and melt the burn line. The wire is wound through three holes on each side to ensure it remains in place even without solder. Baseline part: 30 gauge nichrome 80 round resistance wire. 4”

G- Burn Line The burn line is fishing line that wraps around the antenna booms to hold them in the stowed position. The line also wraps around the burn wire, which melts the line to release the antenna booms. Baseline part: Berkley fireline microfused with dyneema .15 mm Diameter

F- +Y board

H- Slot

While securing the antenna, first glue the booms into the windform bracket. There are several lulzbot-printed brackets measured to hold the booms at the right angle during drying, or new ones could be fabricated. Dipole angle did not significantly affect performance as long it's generally 90-100 degrees. Recommend at least three drying periods, two to ensure the holes are filled, and then one more for a cone sealant.

Wrap the conducting wire around the base of the booms and run it underneath the bracket. Screw the bracket to the +Y board. This board can be attached to the satellite at this time, or the antennas can be coiled while the board. For ease of running the fishing line through the slot, it might be easiest to use a guide string with a loop running through the slot before any assembly occurs.

Ensure that the bottom right corner of the +Y board is using a long M3 screw with a heatset insert as a spacer.

Secure the antenna as in the above diagram, using forceps to lock it into place. The antenna coil must be placing tension on the corner post to make sure everything stays in place. The orange boom must form a corkscrew loop or it'll get caught on deployment. The position of this loop isn't important, but it might be easier to manage if you place it to allow it to be secured with a forceps and fishing line as well. Then end of the orange boom should slot into the antenna bracket. The end of the green boom can be adjusted by adjusting the coil. 3mm overhang over the circuit board should be fine.

This process will probably need to be practiced a few times, tweezer might be helpful. Use the black "flight-heritage" fishing line. The two loops in the diagrams can be formed by doubling the line and tying an overhand knot in the line. At that point, carefully pull the ends until the loop is small enough to be appropriate.

Tension is achieved by feeding the free purple end of the line through both loops and using them as single pulleys. Then tie off the line with a square knot near the purple loop (red area on diagram). The booms should be putting additional tension on the fishing line to hold everything tight.

I left a fully secured loop in the Skilling Lab before leaving with a date on it. It can be maintained as an example or released to make sure that the system is stable after being coiled longer than I was able to test.

The POC for this information is Matthew Kaseman. Preferred contact is via email.