STELLAR

STELLAR is designed for the 2023-2024 Undergraduate Team Space Design Competition, aiming to provide a high resolution topography and radar mapping as well as study the Venusian atmosphere and evolution of the planet. STELLAR consists of Eos, a Venus orbiter that will house 4 astronauts, and Lucifer, a balloon probe that will deploy from Eos and will be controlled by the orbiting crew. The mission will serve to fill the current absence of data regarding the level, if any, of seismic activity on Venus, as well as the absence of data regarding surface material composition. It will also serve to reinforce historical missions by supplementing existing topographical maps, atmospheric dynamics and conditions data, and more with its own detailed, high-resolution data.

Lucifer - Variable Altitude Balloon

Mechanical Design

A balloon-in-balloon concept is designed to incorporate advantages of Superpressure and Zero Pressure balloon. The inside balloon in this concept is always pressurized (making it a de facto superpressure or SP balloon) while the outside balloon is unpressurized that expands or contracts depending on the helium gas distribution and altitude. Moving helium gas between the two balloons modulates the buoyancy and effects altitude changes. This balloon-in-a-balloon design features two key advantages for long-duration mission:

Any helium gas that leaks out of the inner balloon is captured by the outer balloon and not lost. The net effect will be a small increase in pumping energy required to put it back into the SP balloon.
The inner balloon is protected by the outer balloon from the sulfuric acid. This allows for the inner balloon structure to be optimized for strength to carry the pressure loads, leading to a more reliable, mass-efficient structure.

Control System

The control system of Lucifer is designed to actuate the pumping system and collect engineering data for the vehicle's health. The system is divided into two sections: pumping and data collection. The pumping system consists of two valves and a pump to move helium between the outer and inner balloon. All components are controlled using a DC relay board and a 24V battery shown in Figure 6. The data collection system incorporated onboard sensors to collect data for the atmospheric pressure and temperature, outer balloon gas pressure and temperature, inner balloon gas pressure and temperature, vehicle’s height, and the pump system state.

Human In The Loop

The crew control is critical for mission success, as emphasized by the AIAA RFP requirements mentioned above. The crew will be responsible for Mission Execution and Monitoring of Lucifer balloon. Based on Figure , the crew will use Vehicle State Estimation and Vehicle’s Health data provide by Pump Control for Flight Planning and Failure Detection. The data from these two subsections will help crew determine their next course of action in Flight Control. If they wish to increase altitude, helium gas will be pumped into outer balloon

Instrument

Venus Emissivity Mapper (VEM)

Venus Emissivity Mapper (VEM) is a multispectral, infrared imaging spectrometer that views the surface through five infrared spectral channels to provide a multichannel, global map of igneous rock type and iron/silica mineralogy on Venus. In addition to surface composition study, the VEM also studies and collects data from the atmosphere for water vapor to determine volcanic activity. The VEM will be attached to the balloon to record Venus’ surface in a narrow infrared light wavelength ranging from 700 to 1,000 nanometers. Different types of rocks and minerals reflect light in different ways that reveal their compositions. Using this information, VEM will record the spectra profile of each component at different wavelengths to detect chemical fingerprints of various surface materials. The narrow wavelength also helps prevent the sensors from being obscured by the dense clouds of carbon dioxide that absorb most of the light from the surface.

Infrasound Remote Sensing (IRS)

Infrasound Remote Sensing (IRS) uses a barometer to detect low-frequency (< 20 Hz) acoustic waves known as infrasound. This low-frequency vibration has been detected from earthquakes and volcanic activity on Earth. Due to its dense atmosphere, the energy from seismic activity couples with the Venusian atmosphere up to 60 times stronger than Earth, offering a unique opportunity to explore the internal structure of Venus using floating balloons. The data collected from this sensor will help reveal the past and current volcanic activity as well as the evolution of Venus.

Venus Interferometric Synthetic Aperture Radar (VISAR)

Venus Interferometric Synthetic Aperture Radar (VISAR) is an interferometer that uses a synthetic aperture radar approach to generate global radar maps of Venus' surface and topography and reveal the evolution of Venus. The VISAR will not only improve resolution of topography and radar mapping but also measure active deformation. The interferometer will obtain radar images of the same location at different times to determine stress and strain in that area. This data will help our scientists determine whether Venus is still active or not. .

Gravity Study Instrument (GSI)

Gravity Study Instrument (GSI) is an instrument that read and interpret the radio signal link between the balloon and Deep Space Network (DSN). Similar to gravity science investigation on previous planetary exploration missions like Dawn, Cassini, and Juno, the GSI connects the telecommunications system and the High Gain Attena (HGA) with DSN to form a giant science instrument between Earth and Venus. As the balloon circumnavigate Venus, the GSI will measure the moment of inertia factor MOIF), a quantity that describes the material distribution inside a planet. The instrument also map the thickness of Venus’ crust, heat flow to reveal its past evolution and interior composition. This data will be use to determine the size and state of Venusian as well as the planet rotation including wobble on axis.