# Presentation: 210032

## Extreme Temperature Design Techniques for a Venus Exploration S-band Transmitter

- Robert H. Sternowski
- Softronics Ltd., Cedar Rapids, IA
- Tel. +1.319.447.1446
- Email  bobs@softronicsltd.com

## Outline

- Who are we
- What are we doing, how did we get into it
- Key problems
- Solutions
- Environmental tempering
- Working source list
- Preliminary system architecture
- Novel test chamber
- Summary

## Who Are We?

- Softronics Ltd. is a small business focusing on advanced radio technologies and product design for military and commercial applications
- Auburn University, Dr. R. Wayne Johnson, Director, Laboratory for Electronics Packaging and Assembly (high temperature die attach and bonding)
- Iowa Space Grant Consortium, Dr. William Byrd (test facilities, thermal analysis)

## What, How?

- Bid on NASA SBIR topic in 2004
- Proposed an S-band telemetry transmitter that is mounted in _*exterior ambient 465*__*°C*_
- Won a Phase I study award
- Incinerated many objects in proving that we could really do that (transmit _*and*_ incinerate...)
- Won a Phase II prototype award
- Honing our techniques and trying not to incinerate as many objects....

## Key Problems

**Venusian ambient!!!**
- 465°C temperature
- 90 barr pressure
- 97% CO2
- Sulfuric acid
- Later advised that densities worst at altitude, minimal problem on ground, count on protective transit shroud

## The Solution

- Our innovation: exterior transmitter heatsunk to the ambient CO2 atmosphere
- Objective: minimize mission size, weight by eliminating cooling for transmitter
- Past efforts: cooled pressure vessel
- Key technologies:
- Silicon Carbide transistors
- “Olde Tyme Radios”

## Our Original Concept

## Environmental Tempering of Design

- No sulfuric acid to worry about
- Do not need exotic acid-resistant case
- None of electronic components are pressure sensitive
- Do not need pressure vessel
- “Leaky gasket” sealed case to protect against  particulates, GVS (green Venusian slime) but allow transit/landing equalization
- Components unaffected by CO2

## The Solution

- Silicon Carbide (SiC) transistors
- High temperature (operate 600-1000°C)
- Radiation hard (operate inside nuclear reactors) to survive space voyage exposure
- Processed at 2000°C in manufacture
- FT of 10 GHz (will work at S-band, 2 GHz)
- We had just finished two years on a military project learning how to use them
- Using commercial die by Cree Inc.

## The Solution

- “Olde Tyme Radio” (with apologies to Marconi...)
- Obvious that no modern components will survive (much less work) at 465°C
- We have the charred remains to prove it....
- Only silver solder, welding or mechanical connections will survive (or NO connections)
- We stepped back 100 years to find a survivable component solution

## The Solution

- “Olde Tyme Radio” *continues....*
- All parts are metalselected, cut and bentfor the desiredelectronic properties
- No organics!
- No solder!
- (No wax, paper, wood, etc...)

## Our Approach

- SiC transistors
- High temperature die attach/bonding
- Novel heatsinking
- Handmade metal/ceramic/glass components
- Fewest possible parts
- Oscillator (7), amplifier (6)
- Fewest possible connections
- Sealed but unpressurized case

**10 watt**
**Osc**

**40 watt**
**Amp**

## Working Source List

- Brass
- Copper
- Steel
- Silicon Carbide
- Diamond
- Ceramic
- Glass
- Nichrome

- VHT engine paint
- Ceramic, 1500°F, priorNASA spin-off
- Rutland Silicon Chimney Cement
- 2500°F
- Silver solder
- Jeweler’s welder
- Gold bonding
- Hi-temp die attach

## Preliminary System Architecture

## Testing the System

- Needed a low-budget means of simulating the Venusian environment
- Dr. Byrd suggested the “Ideal Gas Law”:
- Fill a sealed test chamber with the right CO2 pressure at room ambient, heat to Venus temperature and produce Venus pressure
- Bought a used Autoclave Engineers small reaction chamber, outfitting with electrical penetrations for testing (ISGC)

## Summary

- Took on challenge of exterior ambient transmitter design for Venus (465°C)
- SiC transistors, hi-temp attach/bonding key
- Handmade olde-tyme metal components
- Minimize component, connection counts
- Redundant “fail-soft” architecture
- Novel low-cost test chamber
- Applicable to cold environments