Tech Briefs Magazine - December 2023 - 22

Aeronautics
" MADER worked great in simulations,
but it hadn't been tested in hardware. So,
we built a bunch of drones and started flying
them. The drones need to talk to each
other to share trajectories, but once you
start flying, you realize pretty quickly
that there are always communication delays
that introduce some failures, " said
Kota Kondo, an aeronautics and astronautics
graduate student.
The algorithm incorporates a delay-check
step during which a drone waits a
specific amount of time before it commits
to a new, optimized trajectory. If it receives
additional trajectory information from fellow
drones during the delay period, it
might abandon its new trajectory and start
the optimization process over again.
" If you want to fly safer, you have to be
careful, so it is reasonable that if you
don't want to collide with an obstacle, it
will take you more time to get to your
destination. If you collide with something,
no matter how fast you go, it
doesn't really matter because you won't
reach your destination, " Kondo said.
The researchers tested their new approach
by running hundreds of simulations
in which they artificially introduced
communication delays. In each simulation,
Robust MADER was 100 percent successful
at generating collision-free trajectories,
while all the baselines caused crashes.
The researchers also built six drones
and two aerial obstacles and tested Robust
MADER in a multiagent flight environment.
They found that, while using
the original version of MADER in this
environment would have resulted in seven
collisions, Robust MADER did not
cause a single crash in any of the hardware
experiments.
" Until you actually fly the hardware, you
don't know what might cause a problem.
Because we know that there is a difference
between simulations and hardware, we
made the algorithm robust, so it worked in
the actual drones, and seeing that in practice
was very rewarding, " Kondo said.
Drones were able to fly 3.4 m per second
with Robust MADER, although they had a
slightly longer average travel time than
some baselines. But no other method was
perfectly collision-free in every experiment.
In the future, Kondo and his collaborators
want to put Robust MADER to the
test outdoors, where many obstacles and
types of noise can affect communications.
They also want to outfit drones
with visual sensors so they can detect other
agents or obstacles, predict their
movements, and include that information
in trajectory optimizations.
For more information, contact Abby
Abazorius at abbya@mit.edu; 617-2532709.
Coil-On-Plug
Igniter for Reliable Engine Starts
Compact igniter reduces thermal-vacuum corona discharge issues.
Johnson Space Center, Houston, TX
I
nnovators at NASA Johnson Space Center
have developed a coil-on-plug ignition system
for integrated liquid oxygen (LOX)/
liquid methane (LCH4) thermal-vacuum
environment propulsion systems operating
in a thermal vacuum environment. The innovation
will help quell corona discharge
issues and reduce overall mass.
Spark-ignition devices have proven
to be a high-reliability option for LOX/
LCH4 ignition during development of the
Integrated Cryogenic Propulsion Test Article
(ICPTA) main and reaction control
engines (RCEs); however, issues including
spark plug durability (ceramic cracking)
and corona discharge during simulated
altitude testing have been observed, contributing
to degraded spark output and
no-light engine-start conditions.
Innovators discovered that ignition
system reliability could be improved
and weight reduced by eliminating the
traditional coil and spark plug wire. To
achieve this result, engineers made the
innovation by modifying an automotive
coil-on-plug igniter to provide new high
sparking energies at the point of combustion
using low supply voltages.
The coil was modified by vacuum-potting
it into a threaded interface that
mounts into existing spark plug ports on
the ICPTA main engine and the RCEs.
22
Engineers fabricated custom electrode
tips that were thread-mounted into the
potted coil body. Epoxy insulation was
chosen with high dielectric strength to
maintain insulation between the electrode
and threaded adapter.
Vacuum potting successfully prevented
pressure or vacuum leakage into the coil
body and maintained spark energy and location
at the electrode tip. Successful hotfire
ignition was observed at sea-level, altitude,
and thermal-vacuum for both ICPTA
RCE and main engine igniters down to
10-3 torr, which approaches the vacuum of
cislunar space.
The coil-on-plug configuration eliminates
the bulky standalone coil-pack and
conventional high-voltage spark plug cable
by combining the coil and the spark
plug into a single component. The test
campaign successfully proved that coilon-plug
technology can enable integrated
LOX/methane propulsion systems in
future spacecraft.
NASA is actively seeking licensees to
commercialize this technology. Please
contact NASA's Licensing Concierge at
Agency-Patent-Licensing@mail.nasa.gov
or call at 202-358-7432 to initiate licensing
discussions. For more information,
visit https://technology.nasa.gov/patent/
MSC-TOPS-105.
www.techbriefs.com
Top: Conventional spark plug with external coil
and high voltage-cable. Bottom: Coil-on-plug
spark plug system with high voltage cable eliminated.
(Image: NASA)
Tech Briefs, December 2023
https://technology.nasa.gov/patent/MSC-TOPS-105 http://www.techbriefs.com
Tech Briefs Magazine - December 2023

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