# Presentation: 828230

## BALLOON FOR LONG-DURATION STUDIES OF THE ATMOSPHERE OF VENUS

**BALLOON FOR LONG-DURATION STUDIES OF THE ATMOSPHERE OF VENUS**

**K.Baines,  J.Hall, V.Kerzhanovich, S.Stephens, A.Yavrouian, Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, USA **
**M.Said, D.Fairbrother, NASA Wallops Flight Facility, Wallops Island, VA, USA**
**C.Willey, C.Sandy,  J. Ware, T. Frederickson,  ILC Dover Inc, Frederica, DE, USA **

## Why Balloons on Venus?

**Key questions can be addressed**
**Origin and evolution**
** ****measurements of noble gases distribution/isotopes**
**Global circulation**
**balloon tracking, on-board meteo**
**Volatiles and organics**
**sulfur cycle and active gases measurements**
**Middle cloud meteorology**
**on-board meteo/nephelometer, tracking**
**Surface-atmosphere interaction**
**spatial and temporal variability of SO2 and other gases**
**Long-duration (potentially many days) when flying above extremes of deep atmosphere**
**Global coverage: circumnavigate in several days with superrotation + meridional circulation **
**Carrier for deep atmosphere/ surface drop-sondes**
**Less expensive,  no landing and extreme environment risks**

## 3.5 m diameter spherical superpressure balloons. Barebones science package

Material – sulfuric acid resistant fluoropolymer fabric coated with fluoropolymer, 300 g/m2 

12 kg balloon, 2 kg helium, 6.9 kg gondola. Payload mass fraction = 0.33

In 46 hours traversed ~1/3 of Venus circumference in equatorial zone (+/-7o) at ~54 km altitude in benign thermal environment, slowly losing superpressure

**3.5 m diameter spherical superpressure balloons. Barebones science package**
**Material – sulfuric acid resistant fluoropolymer fabric coated with fluoropolymer, ****300 g/m****2**** **
**12 kg balloon, 2 kg helium, 6.9 kg gondola. ****Payload mass fraction = 0.33**
**In 46 hours traversed ~1/3 of Venus circumference in equatorial zone (+/-7****o****) at ~54 km altitude in benign thermal environment, ****slowly losing superpressure**

**Twin VEGA Balloons – The Only Planetary Aerial Vehicles So Far**

## Need for Advanced Balloons

**Why not re-fly VEGA balloons?**
**Material is too heavy**** – inefficient for more capable payloads**
**Highly permeable**** – not long lasting**
**Poor optical properties**** - high temperatures, superpressure and leak rate on day side**
**Balloons for advanced missions have to be robust and capable for**
**Heavy payloads:**** ****>40 kg**
**Long duration:**** ****> ****6 days**
**Global flights:**** ****multiple day/night cycles and circumnavigation at any latitude **
**High payload mass fraction:**** ****>0.5**
**Tolerate Venus environment:**** ****clouds of 85% sulfuric acid, vertical winds up to +/-3 m/s**

## Balloon Design Approach

**Benign thermal environment:**** ****altitude 54-56 km**
**Capable for long duration:**** ****superpressure (constant volume) balloon**
**Sphere:****  ****most mass efficient**
**Robust:**** ****safety factor (ratio of burst load to actual load) >2.5 in the most adverse combination**
**Low gas permeability:**** ****metallized film**
**Minimum day/night temperature variations:**** ****minimum optical absorptivity/infrared emissivity ratio (********)**
**Tolerate sulfuric acid of Venus clouds:**** ****fluoropolymer outside layer**

## Balloon Flight Simulation

**Full trajectory simulation after balloon inflation**
**5.5 m diameter balloon @55.5 km**
** ****a/e= 0.19 (25 ********m silverized Teflon)**
**1.5 multiplier** **to radiation model for worst-case**
**Vertical winds up to 3 m/s (maximum encountered by VEGA balloons) **

## Flight Simulation Results

| Latitude,
deg | Vertical wind, m/s | Balloon tempera-ture, C | Maximum superpressure, Pa | Material load, N/m | Safety factor
(prototype) |
| --- | --- | --- | --- | --- | --- |
| 0 | 0 | 64 | 9350 | 12580 | 3.8 |
| 0 | 3 | 56 | 11780 | 16400 | 3.0 |
| 30 | 0 | 55 | 8070 | 11240 | 4.4 |
| 30 | 3 | 49 | 10810 | 15050 | 3.4 |
| 60 | 0 | 41 | 5720 | 7970 | 6.5 |
| 60 | 3 | 35 | 8420 | 11720 | 4.5 |

## Full-Scale Prototype Balloon (“Alpha”) Has Been Designed, Built and Tested by JPL/WFF/ILC Dover Team

| Balloon metric | Value |
| --- | --- |
| Diameter | 5.5 m |
| Envelope areal density | 176 g/m2 |
| Balloon mass | 23.7 kg |
| Payload mass | 44 kg |
| Helium mass | 7.8 kg |
| Payload mass fraction | 0.58 |

**Single-shell composite material**

- ILC Dover proprietary sulfuric acid resistant adhesive for outer layer

## Comprehensive Mechanical, Thermal and Sulfuric Acid Tests of Material Met Expectations

| Parameter | Specification | Value |
| --- | --- | --- |
| Areal density, g/m2 | ASTM D3776 | 176 |
| Thickness, mm | ASTM 1777 | 0.17 |
| Tensile strength @23 C (warp), kN/m | ASTM D5035 | 71 |
| Tensile strength @23 C (fill), kN/m | ASTM D5035 | 57 |
| Elongation at break (warp), % | ASTM D5035 | 5.3 |
| Elongation at break (fill), % | ASTM D5035 | 7.0 |
| Helium permeability, liters/m2/day | ILC  STP 029 | ~0 |
| Seam tensile strength (warp), kN/m * | ASTM D5035 | 45 |
| Seam tensile strength (fill), kN/m * | ASTM D5035 | 57 |
| Tensile strength @75 C  (warp), kN/m | ASTM D5035 | 60 |
| Tensile strength @75 C  (fill), kN/m | ASTM D5035 | 47 |

|  |  |  | Sulfuric Acid Concentration, % |  |  |  |
| --- | --- | --- | --- | --- | --- | --- |
| Component | Test temp, C | Test duration, day | 75 | 85 | 92 | 96 |
| Balloon material | 25 | 7 |  |  |  |  |
| Balloon material | 70 | 7 |  |  |  |  |
| Balloon material | 70 | 2 |  |  |  |  |
| Balloon material bi-fold | 25 | 14 |  |  |  |  |
| Balloon material bi-fold | 70 | 2 |  |  |  |  |
| Balloon seam | 25 | 6 |  |  |  |  |
| Balloon seam | 70 | 2 |  |  |  |  |
| Vectran fabric | 25 | 2 |  |  |  |  |
| Vectran fabric | 70 | 7 |  |  |  |  |
| Mylar film | 25 | 14 |  |  |  |  |
| Mylar film | 70 | 2 |  |  |  |  |

****Polyester fabric based seam tape, stronger Vectran fabric for the next prototype***

| Negligible effect | External discoloration and/or wrinkling but no evidence of acid penetration | Not tested |
| --- | --- | --- |

## No Helium Leak In 2-week Test

**Balloon inflated with ~50/50% helium-nitrogen in JPL SAF clean room**
**Known amounts of nitrogen added two times to vary superpressure level**
**Monitored buoyancy, superpressure, ambient pressure, temperature and humidity to calculate mass of gas**
**No noticeable leak measured**

## Aerial Deployment and Inflation Not Major Risk Anymore

**August 1998, H~1 km: 3-m spherical 12 ********m Mylar balloon **

**June 2002, H~30 km: 11-m pumpkin 20 ********m PE balloon **

**May 2006, H~30 km: 10-m spherical 12 ********m Mylar balloon **

**June 2006, H~1 km: 11-m 50 ********m polyester airship**

**Progressively successful aerial deployment and inflation flight tests at much higher material stress levels**
**No damages or pinholes in numerous hangar drop tests of much weaker 10-m 12 ********m Mylar balloon**

## Summary

**Balloons can be used as long-duration science platforms for global studies of atmosphere and surface of Venus**
**Can carry significant payload mass and instruments to address key questions about origin, evolution and processes on Venus**
**Also closes gaps and provides “ground truth” for orbiter data**
**Prototype of next generation sulfuric-acid tolerant balloon capable for long-duration global flight has been designed, built and tested** **successfully**

**Pack in aeroshell and launch to Venus ****Europeans are waiting in orbit!**