NIAC 2016 Conference
Transcription: Paul Fischer
Bruce Wiegmann, NASA Marshall Space Flight Center
HERTS/Electric Sail background information
modeling
tether and deployment specifications
and spacecraft design
Contributions from universities, labs, and technical schools across the country
Distinction of a solar sail from an e-sail
E-sail converts sun’s energy through electrostatic repulsion
wire sheath extends and pushes positively charged protons through
these positively charged tethers are quite different in punch and design from an e-sail
thrust drops by 1/r^2 for the solar sail and 1/r^1.16… for an e-sail
e-sail will provide higher velocity, and have a slower degradation of thrust in dark spots
Voyager took 35 years to reach edge of the solar system, an e-sail could shorten that time significantly
How to recreate a tether deployment in an area with a flat floor, should be ready shortly
the cost came to 50,000 for this research
Results of the particle and sail deployment simulations
data generated was reproducible, a charged wire repulsion
ion source and charged box there >>> tunnel without a wire
deflection of protons creates an angle and temperature which will be discovered with these simulations
diagnostic suite to measure ion flow, has yielded good data
Updating MALTO model (Mission Analysis Low Thrust Optimization)
the idea is to change the thrust drop ratio and ??/ ratio
Extra space designers were put to work on a couple billion dollar mission, requiring RTG propulsion
creating a box-set proof that the e-sail can actually work
Can we package it into a 12U box?
three conditions for potential success, the project had failed two years before
Deploy
Accelerate
Steer
acceleration goal is triple that of competing research and many times that of any existing system
Hub and Spoke > Hybrid > Barbell
neither the first nor the third would be feasible at a full scale
Initial issues with the 12U system propellant mass and combinations of 6 U systems which violated maximum spin rates
the hybrid of 10U and two 1U units did not burn out
Use of the NEA scout 6U design with a 6 kV power supply and other modifications
development of a tether trade tree, for advantages of different materials
Materials
synthetic > organic > metallic
Miralon (CNT)
amber strand leading contender
Aluminum
copper
SOS is the vehicle of choice for deployment, because not many NASA vehicles are outside of orbit
Upper stage> 10 or 11 rideshare payloads, which will eject from this stage
Detumble - drives propellant to spin out, 800 grams of cubesets
Uncouple
200 watts of electricity total for solar array deployment, 16 km in approximately 6 hours>> 8 rotations per day
when spacecraft is 30 degrees out of the ecliptic plane, a solar array can be conceivable
QA
As the model is expanded to actual size, the forces at work will also grow, so the 1/r^1.16… is correct
Scale of animation yields questions about the tether system…
It is outside of the Earth’s magnetosphere 2 different electron transmission cables are provided
Initial skepticism was overwhelmed by personal model on a small scale which proved that this actually did work! Would the solar field be guided by the field lines of the magnetic charges which [exist in space or from craft?] are extant
Yuri Millner and interstellar team are interested in this
Transfers for Lunar extreme environments: Adrian Stoica
Project is currently in phase 2
concept of transformers -
autonomous reflectors deployed from small surface to large surface projects
provide continuous solar illumination into permanently shaded craters
creates an infrastructure that provides power and thermal control to robots as a service
Shape changing robotic space systems that redirect energy
on the rim, can also serve as communication relays
This is not a new thought, but the story of how to bring the sun into the dark place sparked this thought >> Norway in Rio Kant, reflectors provide 50 meters sun exposure
Space mirrors starting with Almond Albet and later Ehricke have been explored conceptually
1) deposits of hydrogen and oxygen are extant
2) tech to power ISRU is permanently shaded areas is lacking
3) locations on the rim of Shackleton crater have long, yet discontinuous, periods of illumination …at most there might only be 3 days (2.5ish) of darkness, so this is also a period which will have to be dealt with
Phase 1 Findings: relatively large reflectors, will necessitate light and small packing
RTG may be ok for prospector rover, but not enough to power ISRU
The rover must survive periodic shortages in hibernation mode
re-usable data
ISRU of icy regolith necessary to extract water, hydrogen, and oxygen
evaluate the possibility to obtain continuous illumination
develop concept and reduce uncertainties, inc. material, unfolding of TF from compact to full sized
Vision
Develop a Lunar Pole South Illumination ???…
capacity of the SPI
Lunar ISRU potential to fuel travel to Mars
Lunar LH2/LO2 propellant from Shackleton Crater may be sufficient
Sustainable and affordable human-mars exploration architecture using self-propelled tanks refueled on Moon
five hundred days of Mars exploration enabled
Deep-Space habitat will use some tanks of fuel
one full tank will be waiting at Leo, while four empty tanks return to Moon for refueling
10 tons of water can be generated per day, and produce 7.5 tons of propellant
Regolith water resource: one meter depth with 5-10% of ice
Total power needs for ISRU
6MW for extraction of water, 50 kJ/g, 24kJ per gram for electrolysis 10 t/day
13MW solar power, 3 MW direct heat and 10 MW energy
Summation of results
LOLA data and 3D models for computer generation
tools allow pretty good comparison of Ray-Tracing and Horizon measurements
Redirection from a region into a two flat mirror system >>>complete illumination along the rim>>> actual illumination through the transformer
should the reflectors be pure or should they be concentrated into lasers?
eg origami opening>>> properties of Spiral and Concentric Crease Patterns
composing solar panel infrastructure, and importance of taking advantage of the Moon before traveling to Mars…
QA No clues on the amount of harvestable ice which might be there, and whether that ice might be needed for lunar settlement
there appears to be enough water for 3000 years of travel to Mars using this method, but technical issues remain
it could be 2000 years, but yeah…
Access remains an issue, shackelton several kilometers across and deep
actual landing and launch will occur from crater.
Michael Paul, presented by Dr. Timothy Miller
Why: Stored Chemical Energy System
continuation of a phase II project
Need:
Power for spacecraft in sunless regions
battery-power leads to short missions (hours)
Not enough plutonium to go around
is there a sweet spot in the design space of missions for combustion?
Combustion of Lithium fuel where a Navy research station did work with power systems
use of all sorts of metals as oxidizers and products are more dense than the actual fuel, which will allow those metals to stay in the system [unlike leaded gasoline, which leaked and combusted into family homes with indoor generators]
Phase two effort follows design for five-days (120-hrs) on the surface of Venus
8Lithium +Sulfuric hexa-Flouride>6dilithiumiSulfite+Heat
standard heat of reaction at 298K is ?? kW
prior stirling demonstration system:
fully integrated system (~.5m diameter)
3kW Stirling Engine
37% efficiency
80 hour Wick Combustor Operation (Fuel exhaustion)
Horizontal, Cylindrical Tank when used has a void space from the Lithium which was present, as products of combustion freeze at a different temperature than Lithium, which can create cracks and breaks in the containment chamber
Lithium Oxide has the highest temperature reaction, so the necessity to create lithium carbide presents
96.5% CO2 and 3.5% N2
in order to obtain clean Lithium, these products must fall away completely
a little over 4 times the system specific energy over a Nitrogen/sulfur based battery
9” by 14” combustion model
1000 degrees fahrenheit yields the blue flame
at 1250 degrees, a scarlet flame is demonstrated which allows some smaller byproducts to form
Li and CO2 yields alot of crap along the top, as the temperatures run began to fluctuate dramatically
a nice sustained combustion process occurs for about 100 minutes before the lithium level sinks below thermal couple one, and proceeds through couple two into couple three
Lithium oxide melts or freezes at a very high temperature, where lithium separates from the crud
this necessitates a wider combuster… will be accomplished shortly
circumferential defraction??? as lithium runs up the sides of lithium oxide and carbide
time progression yields the progression of free carbon
moles products vs. moles CO2
trying this with Nitrogen will be the next goal
For an application on the lunar South Pole, with the engine operating at 2 kW and rejecting heat to only 50 K a run time of 150 hours can be expected.
QA Occupational safety concerns about Lithium, fire safety?
No government body on earth is more restrictive about fuel than US Navy systems, so solid lithium is actually quite benign, unless it accumulates hydrogen… must be used with caution, but is much safer than plutonium or other products
fairly large body of data using no-gravity simulations, but in the third system with the products falling away there may be complications, but there is no indication that the reaction will not occur in zero gravity.
combustion products could sink, but carbon dioxide lithium success does depend on keeping these by-products from sticking to the wall
the holy grail of not having to take an oxidizer
This is the first time of running this project with a Stirling Engine
dependence on segregation has been displayed to be not entirely present
The Navy system was deployed as a steam system
