SPACE :: Projects
We stress practical hands-on experience on real-life projects funded by international collaborators from industry, government, or a combination of the two. SPACE researchers are currently actively working on these projects:
1. Asteroid Exploration and Mitigation Platform (AEMP) Project
The Asteroid Exploration and Mitigation Platform (AEMP) conducted by the SPACE builds upon the foundation of efforts. Understanding the trajectory and composition of the asteroid is a necessary requirement to do any kind of mitigation. In order to know if an impact is likely, the current position of the asteroid must be known to within tens of meters. By placing a beacon near the asteroid, Earth-based radio tracking can improve our knowledge to this level in six months. During this period, a sensor suite on the spacecraft will improve our understanding of the composition, albedo, size and shape of the asteroid.
SPACE will test and produce the albedo change technology that is a core part of the AEMP project. Rather than rely on an operational spacecraft for years or decades, AEMP will create a small, permanent force on the asteroid by changing the albedo of the asteroid. The force, known as the Yarkovksy effect, pushes the asteroid toward its dawn side, creating a consistent, trajectory-altering perturbation.
Surface Albedo Treatment System
A secular force (non-oscillatory as opposed to periodic) called the Yarkovsky Effect acts on all celestial bodies, but especially on small astronomical objects such as asteroids. The Yarkovsky Effect is the result of anisotropic (non-uniform) heating of a celestial object, which depends on the reflectivity of the body's surface. The side of the asteroid that faces the sun will be heated more than the side opposite of the sun. As depicted in the following figure, as the sunlit side of the asteroid rotates away from the sun, the warmer dusk side radiates more energy than on the cooler dawn side, hence generating a force.
The surface albedo treatment system (SATS) can change the albedo, a measure of surface reflectivity, and thus change the force due to the Yarkovsky Effect. This simple technique allows a permanent change in the trajectory of the object long after the termination of the spacecraft as opposed to transient techniques such as using gravity tractors. Since the surface properties of Apophis are uncertain currently, both light and dark albedo changing mechanisms must be available.
The system implements a tribo dispenser to charge and eject the powders that will land on the surface of the asteroid and stick due to electrostatic attraction, melt, and then cure and adhere to the surface permanently. The powder must be ejected within a certain speed and a certain amount of charge to ensure sufficient attraction to the asteroid surface. The ACP Dynamical Simulator currently under development serves to pinpoint these restrictions through Monte Carlo techniques. Refer to the following figure for a schematic of the deposition process.
A tribo dispenser charges the powder particles through static friction between the albedo changing powders (henceforth known as ACPs) and a long tube as the powders are pushed through by a moving neutral gas such as nitrogen. To ensure sufficient charge transfer from static friction, the material compositions of the tube and the ACPs must be on opposite ends of the tribo series (an electronegativity scale for materials). For creating negatively charged powder, the tube can be made of a material such as nylon and the ACPs a material with similar chargeability as PTFE. The powders are available in colors of white and black to ensure flexibility in trajectory change.
A simple design concept for accelerating the ACPs is to use a low-pressure cold gas thruster. At appropriate times, the valve opens allowing the pressurized gas and ACPs to mix together before injected into the tube. The SATS depicted here is composed of four components: the inert gas chamber, ACP chamber, mixing chamber, and tribo-ionization tube. A prototype tribo-ionization tube will be developed either through independent effort or through a subcontract with an engineering firm like SAMES. Refer to the following figure for a schematic. Alternatively, a pump can be used for gas injection which adds complexity but also adds reliability in case the pressure tank suffers a leak.
The powder itself must fulfill specific requirements such as
- Melt and flow at ~120 C.
- Curability under visible light or infrared from the sun
- Negative chargeability
- Greater than 100 microns diameter to ensure no dust levitation
Since no such powder exists with all such properties, it will have to be developed. Subcontracting the Powder Coating Research Group (PCRG) will aid in that effort.
LEO Demonstration System
The Low Earth Orbit (LEO) flight experiment of altitude 350 km and inclination 46° is the final step in verifying the operations of the payload, the Surface Albedo Treatment System, before launch of the actual spacecraft for Apophis exploration and mitigation. The flight experiment, the Static Preliminary Albedo Demonstration Experiment (SPADE), will test the tribo dispenser payload extensively on a positively-charged flat plate attached to the main body of the cube spacecraft. Through doing this, the satellite will verify multiple aspects of the system:
- Necessary dispensing cone angle
- Flow and powder deposition rates
- Coverage efficiency (a factor depending on the area of coverage and depth of coverage)
- Albedo change of the test subject
The main body of the spacecraft is an anodized aluminum cube of dimensions 40x40x40 cm which fits within ESPA 24 constraints. The static flat surface is attached to a side of the spacecraft and freely exposed to the space environment. The test surface is constructed as a parallel capacitor to simulate natural charging of the sunlit Chondritic asteroid surface. Three regions of increasing roughness from perfectly smooth to extremely bumpy will test effects of roughness on particle curing and adhesion. Though assumed to have an area of 0.22 m2 this size will be reassessed before final vehicle selection.
Prior to dispersion, the albedo changing particles (ACPs) and pressurant will be stored in separate spherical tanks near the tribo-dispenser. As indicated in Figure 1, the tribo-dispenser will be mounted opposite of the test surface, with the barrel angled toward the surface. The particles will spread out in a cone with a circular cross section. Imagery will be collected as the particles are released, electrostatically attracted to, cured, and adhered to the surface.
The tribo-dispenser requires 95 W of power for the duration of the experiment, which runs only for 10-minute intervals. The spacecraft bus itself requires a constant 19.5 W. Power for the spacecraft bus will be provided by solar panels and secondary batteries, while the SATS payload will operate from a distinct primary battery. Torque rods, magnetometers, and coarse sun sensors will be used for attitude control. The communications scheme will utilize a store-and-forward architecture, and using an omnidirectional monopole antenna, CubeSat-class UHF transceiver, a GPS beacon will be integrated to aid acquisition and tracking.
A CCD imager will capture the SATS deposition process, using sunlight for illumination. The frames will be analyzed on the ground to refine tribo-deposition models in the space environment.
We are currently actively working on this project with the help of our sister company ECAPS LLC located in the United States. If you will like to help technically or financially, we'll be happy to accomodate you if you are qualified and interested. Please contact Shen Ge.
2. Asteroid Mining
Asteroid mining is drawing increasing interest in the last year with the establishment of two space companies publicly declaring their common intention of mining asteroids. However, the economics of asteroid mining is barely developed which raises questions on how these companies and future startups will attract enough investment for such a mammoth project. In economics, a net present value that is positive indicates a positive return on a project. No significant additions have been made to Mark Sonter's net present value equation for asteroid mining since he wrote his thesis in 1997. This project serves to address both the technical and economic factors required to determine a future asteroid mining mission's feasibility. Building upon Sonter's equation, this project will introduce new variables to cover the gaps and resolves uncertainties in the previous analysis.
For an overview of our project, look over our presentation first presented at AIAA Houston's Annual Technical Symposium on May 17, 2013 (Version 2.0) and later at the San Antonio OMICS Conference (Version 4). We also made an interim report amongst ourselves:
- Economics of Asteroid Mining (Presentation) Version 4.0
- Asteroid Mining International Project Initial Work (Presentation)
- Economics of Asteroid Mining (Presentation) Version 2.0
Currently, we are working to make this into a white paper which we aim to present at the International Astronautical Congress 2014 in Toronto, Canada. As we spend some time building software tools to help with our analysis, we will also be looking for funding for this project later next year.
The SMOTESS instrument is a configuration of at least four small telescopes for the purpose of detecting near earth asteroids to identify potentially threatening earth-impactors as well as interesting scientific and commercial targets for future spacecraft missions.
A minimum of four telescopes is necessary for redundancy, i.e. if one fails the entire mission can continue. It does not require accurate attitude tracking as in typical space telescope designs since it uses the scan mode imaging technique which has been demonstrated on-ground in the existing heritage system MOTESS. The MOTESS has detected numerous NEAs, with objects ranging from asteroids with diameters about 300 meters such as 1997 MW1 down to asteroids with diameters of tens of meters such as 2003 UY12.
The basic SMOTESS instrument is a copy of the MOTESS instrument and consists of three 14” f/5 paraboloidal mirrors with a 2048x2048 CCD with 12 micron square pixels at the prime focus. The focal length will be 175 cm which produces an image scale of 1.414 arcseconds per pixel. At an average distance of 0.7 AU (Venus-like orbit) with a 24-hour scan rate, SMOTESS has a limiting magnitude detection threshold which is at least 23.
Assuming a lifetime of ten years and a Venus-like orbit (semi-major axis of 0.7, eccentricity of 0.1, and inclination of -15°) and a field of view in the rotation plane of 300° (everywhere except within 30° of the sun) and 2.415° above and below the rotation plane, a six-telescope configuration of SMOTESS is estimated to be able to see ~63% of 40 to 140 meters diameter asteroids after 10 years if placed in a Venus-like orbit. Currently, only 1% of 40 to 140 meters diameter asteroids have been detected. The figure below shows the percentage and number of asteroids detectable with respect to the asteroid size distribution estimated by our preliminary models based upon magnitudes and distributions generated by Bottke et al. and Greenstreet et al. respectively.
We have presented our project at the San Antonio OMICS conference in October 2013. Consider reviewing our presentation below for a more in-depth overview of our project:
We are currently actively seeking funding for this project through our sister company ECAPS LLC in the United States and have submitted several proposals. If you will like to help technically or financially, we'll be happy to accomodate you if you are qualified and interested. Please contact Neha Satak.
Future projects will encompass such areas:
- Space Solar Power Satellite Constellation
- Cooking Tools for Low Gravity
- Self-sustainable Habitation Technologies