A paper presents an algorithm to initialize a formation of N distributed spacecraft in deep space

Hadaegh, Fred

Ploen, Scott

Scharf, daniel

NASA Technical Reports Server

NASA Tech Briefs, May 2007 35
Books & Reports
Development of Vapor-
Phase Catalytic Ammonia
Removal System
A report describes recent accomplish-
ments of a continuing effort to develop
the vapor-phase catalytic ammonia re-
moval (VPCAR) process for recycling
wastewater for consumption by humans
aboard a spacecraft in transit to Mars.
The VPCAR process is implemented by a
system of highly integrated design in
which some power consumption is ac-
cepted as a cost of minimizing the vol-
ume and mass of a wastewater-process-
ing system and eliminating the need to
resupply water. The core of the system is
a wiped-film rotating-disk (WFRD) evap-
orator, which removes inorganic salts
and nonvolatile organic compounds
from the wastewater stream and concen-
trates these contaminants into a recycle-
and-bleed stream. The WFRD evapora-
tor is also part of a subsystem that distills
water from the wastewater stream. This
subsystem operates in a vacuum-
vapor/compression distillation configu-
ration in the temperature range from 20
to 65 °C. Volatile organic compounds
and ammonia, distilled along with water,
are oxidized to CO2, H2O, and N2O in a
packed-bed, high-temperature catalytic
reactor placed at the outlet of the vapor-
phase compressor of the distillation sub-
system. A VPCAR engineering demon-
stration unit is expected to be included
in a human-rated simulation of a mis-
sion to Mars.
This work was done by Michael Flynn,
John Fisher, and Mark Kliss of Ames Re-
search Center; Bruce Borchers of Orbital Sci-
ences Corp.; Badawi Tleimat and Maher
Tleimat of Water Reuse Technology Inc.; and
Gregory Quinn, James Fort, Tim Nalette,
Gale Baker, and Joseph Genovese of Hamilton
Sundstrand Space Systems International,
Inc. Further information is contained in a
TSP (see page 1).
Inquiries concerning rights for the commer-
cial use of this invention should be addressed
to the Ames Technology Partnerships Division
at (650) 604-2954. Refer to ARC-14607-1.
Several Developments in
Space Tethers
Five reports address different aspects
of development of tethers to be deployed
from spacecraft in orbit around the
Earth. The first report discusses proposed
optoelectronic tracking of retroreflective
objects located at intervals or of retrore-
flective coats along the entire length of a
tether to measure lateral motions. The
second report describes digitally con-
trolled spooling machinery that retracts
or extends a tape tether at controlled
speed and tension in the spool isolated
from uncontrolled tension on the out-
side. The third report discusses part of
this machinery that pivots to accommo-
date misalignments between the de-
ployed and spooled portions of the tether
and contains rollers used to exert tension
and speed control. The fourth report dis-
cusses aspects of designs of proposed
electrodynamic tethers, which would be
electrically conductive and would interact
with the magnetic field of the Earth to
exert forces to modify orbits of deploying
spacecraft. The fifth report discusses elec-
trical aspects of designs of electrody-
namic tape tethers, including the use of
solar cells or motional electromagnetic
force to generate currents in tethers and
the use of electron emitters and electron
and ion collectors at opposite ends of
tethers to make electrical contact with
the thin plasma in surrounding space.
This work was done by Andrew Santangelo
and Rich Sturmfels of The Michigan Technic
Corp. and Neal Rothwell of Double R Con-
trols for Marshall Space Flight Center. Fur-
ther information is contained in a TSP (see
page 1).
MFS-31822/4/6/7/30
Design Concept for a Nu-
clear Reactor-Powered Mars
Rover
A report presents a design concept for
an instrumented robotic vehicle (rover)
to be used on a future mission of explo-
ration of the planet Mars. The design in-
corporates a nuclear fission power sys-
tem to provide long range, long life, and
high power capabilities unachievable
through the use of alternative solar or
radioisotope power systems. The con-
cept described in the report draws on
previous rover designs developed for the
2009 Mars Science laboratory (MSL)
mission to minimize the need for new
technology developments. 
The surface fission power system that
would be used consists of a 15 kW (ther-
mal) heat-pipe-cooled reactor coupled
with a Stirling generator to provide 3
kW of electrical power. This power sys-
tem would be compact enough to fit
readily into prior rover chassis con-
cepts, allowing further adaptation of
previously designed MSL elements, in-
cluding the aeroshell and pallet lander
system, with modifications to support
the significant mass added by the nu-
clear reactor and its associated shield-
ing. The estimated mass of the fission
power system, including its mission-spe-
cific shielding, is 1,169 kg.
This work was done by John Elliott of Cal-
tech, Dave Poston of Los Alamos National
Laboratory, and Ron Lipinski of Sandia Na-
tional Laboratory for NASA’s Jet Propulsion
Laboratory. Further information is contained
in a TSP (see page 1). NPO-30865
Formation-Initialization Al-
gorithm for N Spacecraft
A paper presents an algorithm to ini-
tialize a formation of N distributed
spacecraft in deep space. Such forma-
tions will enable variable-baseline inter-
ferometers in future NASA missions de-
signed to study the structure and origin
of the universe. The algorithm de-
scribed in the paper reflects some basic
assumptions: 
1. Each spacecraft is capable of omnidi-
rectional radio communication with
any other spacecraft, 
2. Each spacecraft is equipped with a
limited field-of-view sensor relative po-
sition sensor (RPS) to measure the
relative positions and velocities of
other formation members, and
3. Spacecraft maneuvers must satisfy
Sun-angle pointing constraints to
shield sensitive optical equipment
from direct sunlight.
The formation initialization algo-
rithm proceeds by first dividing the
spacecraft into two groups with anti-par-
allel RPS sensor boresights. Next, the
spacecraft perform a three-phase (in-
plane, out-of-plane, and near-field) sky
search involving synchronized maneu-
vers to ensure full sky coverage while
maintaining front-to-front, simultaneous
RPS sensor lock. During the sky search,
the spacecraft are grouped into two
classes of sub-formations. The initializa-
tion problem is then reduced to the sim-
pler problem of joining the sub-forma-
tions. The paper includes an analytical
https://ntrs.nasa.gov/search.jsp?R=20090041635 2019-08-30T08:17:20+00:00Z
36 NASA Tech Briefs, May 2007
proof that the algorithm is guaranteed
to initialize the formation as required.
This work was done by Scott Ploen, Daniel
Scharf, and Fred Hadaegh of Caltech for
NASA’s Jet Propulsion Laboratory. Further in-
formation is contained in a TSP (see page 1).
The software used in this innovation is
available for commercial licensing. Please
contact Karina Edmonds of the California
Institute of Technology at (626) 395-2322.
Refer to NPO-43040.
DNSs of Multicomponent
Gaseous and Drop-Laden
Mixing Layers Achieving
Transition to Turbulence
A paper describes direct numerical
simulations (DNSs) of three-dimen-
sional mixing-layer flows undergoing
transition to turbulence; the mixing lay-
ers may or may not be laden with evapo-
rating liquid drops. In contrast to most
studies in this field, the general case is
investigated here where both the gas
and the liquid drops’ composition en-
compasses a very large number of
species. The simulations were per-
formed using a mathematical model dis-
cussed in several prior NASA Tech Briefs
articles; the prior studies described a
laminar mixing layer, whereas the pres-
ent study describes a mixing layer that
has all attributes of turbulence. The
model includes governing equations in
an Eulerian and a Lagrangian reference
frame for the gas and drops, respectively.
To mathematically describe the myriad
of species, the model relies on continu-
ous thermodynamics concepts. The
paper succinctly reiterates the model
and discusses results of the new numeri-
cal simulations. Comparisons are per-
formed with previous single-species sim-
ilar simulations and with the laminar
simulations using the same model. The
paper presents several conclusions, the
main one being that differences be-
tween single- and multi-species turbu-
lent flows having the same initial condi-
tions are so significant that neither ex-
periments on, nor theoretical studies of,
single-species flows are adequate as sur-
rogates for studies of multi-species flows.
This work was done by Josette Bellan and
Laurent Selle of Caltech for NASA’s Jet
Propulsion Laboratory. Further information is
contained in a TSP (see page 1).
In accordance with Public Law 96-517,
the contractor has elected to retain title to this
invention. Inquiries concerning rights for its
commercial use should be addressed to:
Innovative Technology Assets Management
JPL
Mail Stop 202-233
4800 Oak Grove Drive
Pasadena, CA 91109-8099
(818) 354-2240
E-mail: iaoffice@jpl.nasa.gov
Refer to NPO-42632, volume and number
of this NASA Tech Briefs issue, and the
page number.


Formation-Initialization Algorithm for N Spacecraft

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