Considerable opportunity exists to improve the systems, subsystems, components, etc., included in the space station bus, the non-payload portion of the spacecraft. The steps followed to date, the challenges being faced by industry, and the progress toward establishing a new NASA initiative which will identify the technologies required to build spacecraft of the 21st century and which will implement the technology development/validation programs necessary are described

Bercaw, Robert W.

Brandhorst, Henry W., Jr.

Faymon, Karl A.

English

NASA Technical Reports Server

N87-26448
SPACECRAFT 2000 - lie CHALI.ENGE OF IHE FUIURE
Henry W. Brandhorst, Jr., Karl A. Faymon, and Robert W. Bercaw
NASA Lewis Research Center
Cleveland, Ohio
Considerable opportunity exists to substantially improve the systems, sub-
systems, components, etc., included in the spacecraft bus, the nonpayload portion
of the spacecraft. There are a broad range of technology advancements which can be
brought to bear to reduce mass and cost and to increase lifetime and reliability.
Over the past several years, the NASA Lewis Research Center has been working with
industry, other NASA centers, and the Department of Defense (DOD) to define a new
initiative that would focus on these issues, while at the same time forging new
industry/government relationships that can lead to substantial benefits for both
parties• The steps followed to date, the challenges being faced by industry, and
the progress toward establishing a new NASA initiative which will identify the tech-
nologies required to build spacecraft of the 21st century and which wlll implement
the technology development/validatlon programs necessary are described in this
paper.
INTRODUCTION
Historically, the primary focus of a spacecraft designer's attention has been
the payload, and thls seems most reasonable. After a11, the payload is the primary
purpose for the existence of a satellite• However, this mode of thinking inevitably
leads us into a delicate trap• The emphasis placed on increasing the sophistication
of the payload (often at substantial risk) in order to accomplish the desired mls-
sion, tends to decrease the attention paid to making substantial improvements in
the spacecraft bus. Figure l demonstrates that the payload comprises only one-
fourth of the total geosynchronous (GEO) spacecraft mass and the ratios are similar
for low-Earth orbiting (LEO) spacecraft. Unfortunately, spacecraft managers are
less concerned with the potential benefits than the risk of making substantial
changes in the bus portion of the spacecraft. It is only when the mass of the
spacecraft approaches launch vehicle capacity that investment in new spacecraft bus
technology becomes compelling One e .... i_ o_ _hi_ i_ fh_ d_v_Inpmpnf by CnMSAT
Laboratories and the U.S. Air Force (USAF) of the individual pressure vessel nickel-
hydrogen battery for geosynchronous applications.
In addition to being three-fourths of the spacecraft mass, the bus (defined as
power, thermal management, auxiliary propulsion structure, attitude control, and
telementry, tracking, and control (Tl & C) incurs about one-half the satelllte's
cost (pretest and checkout). Cost is, of course, the major challenge to be met.
In the commercial world, reduced cost means enhanced revenue or increased competi-
tiveness. Figure 2 shows data demonstrating the sixfold reduction in INIELSAI
utilization charges over the past two decades. In the competitive communications
business, cost reduction Is essential to profitability.
Cost reduction plays an important role in other classes of satellites - from
commercial ventures in low--Earth orbit to satellites whose sole goal is scientific
333
https://ntrs.nasa.gov/search.jsp?R=19870017015 2020-03-20T09:49:48+00:00Z
knowledge. For these, cost reduction is often essential to a profitable product or
the ability to fly the mission. Other major factors, such as increased performance,
which enter into the arena as well will be addressed later.
In late 1984, it became apparent that a new kind of government-supported pro-
gram, one that focuses on the spacecraft bus and enhanced Industry-government part-
nership, might be in the nation's best interests. Over the past two years, we at
NASA Lewis Research Center have been pursuing a path which we hope will lead to a
major new initiative for NASA. It is appropriate now to review the steps that have
been taken and the progress that has been made toward this goal.
PROGRAM DEVELOPMEN1
The decision to pursue developing this new initiative resulted from a series
of visits that the Lewis staff paid to industry in the spring of 1985. The objec-
tive was to obtain Industry's view of the critical problems it was facing in its
satellite business ventures. Nine organizations were visited as shown in figure 3.
The range of business orientation spanned government (NASA and military), commercial
communications, and communications operations. Critical concerns were identified.
These included reducing spacecraft related costs and subsystem weights, increasing
system lifetimes and reliability, and reducing technical risks. It is important to
note that each company saw specific future technical needs somewhat differently.
However, there was consensus that there was a real need to address the development
of the spacecraft bus technologies.
The initial program focus was aimed at the broad range of satellites that fall
generally into the classification of mass-llmlted missions. These include GEO
satelllte's and platforms, LEO polar satellites and platforms, and planetary space-
craft. This distinction, while somewhat arbitrary, is certainly helpful program-
matlcally. It is also obvious that advances made in one class of satellites will
be transferable to others.
It should be noted that mass-llmited missions really reflect Earth-to-orbit
booster limitations. This is most clearly shown in figure 4 which demonstrates the
situation in power. For this figure, the power was computed from the known mass-to-
GEO capability of the booster stage (IUS or STS/centaur), the 25 percent mass due
to the power system, and the specific mass of the power system. Current technology
benchmark was taken as the TDRS power system which was 7.2 W/kg for solar array,
battery, cabling, and power management. With present technology a stringent limit
is placed on the power available in orbit. Advanced technologies can substantially
eliminate such restrictions. It is important to note that a 40 W/kg power system
could be built from technologies currently under development by NASA OAS1 (figure
5). Similar advances are possible in all other areas of the spacecraft bus. It is
entirely possible to double the payload mass fraction by focusing attention on
improvements in the bus and in the design of spacecraft. This additional mass can
be used to enhance reliability, add lifetime, or increase revenue.
Finally, it was also clear from these visits that international competition
was becoming intense and aggressive. A cursory examination of foreign developments
in power and electric propulsion showed significant activity that was promising
enhanced capability. For example, figure 6 denotes the activity in European solar
array development overlaying a projection by Pierce (RCA) of satellite power needs
up to the next century. The European solar array developments are all available
334
today (they are arbitrarily distributed over time to showdetail). Similar U.S.
array developments have been minimal. Figure ? demonstrates the increased voltage
of European satellites in contrast to the 28 Vdc U.S. standard. Increases in vol-
tage permit substantial reductions in cabling mass. Figure 8 shows the flights of
electric propulsion systems by foreign sources, while U.S. technology has been dor-
mant for nearly two decades.
With these examples, it is clear that there is great potential for substantial
improvements in all areas of the spacecraft bus. Industry and government agree.
lhe question is "how to proceed?"
PROGRAM APPROACH
The first step was to establish a steering committee comprised of industry,
several NASA centers, and critical DOD organizations. This group reached agreement
on several key points. First, they emphasized that a government/Industry
partnership was desirable and in the nation's best interest. The hope is that a
government/Industry relationship can be developed in the space arena which parallels
the one that exists in the aeronautical arena. In this partnership the government
supports hlgh-rlsk research; industry takes the results and turns them into com-
mercial advances. The challenge is to expand the technology avallablllty time
horizon of industry and to bring government-sponsored research more near term.
Secondly, a total system approach at the spacecraft level should be used to
define technologies for development. The technology developments should be focused
and a combination of existing, modified, or new NASA and industry IRAD programs.
_he challenge will be to maintain proprietary rights within the company and to
establish a program wherein participating organizations would develop those tech-
nologies that they view to be in their best interest. The program is not envisioned
to be the traditional program in which a system is defined (e.g., a 40 W/kg power
system), and a competition ensures with an organization ultimately being selected
to perform the work. It is clear that many challenges must be overcome to make
this approach a reality.
Next, many supporting technology issues may also have to be addressed - manu-
facturablllty, testing, servicing, supportability, etc. It will be essential to
understand the operating environment of the 21st century and how it will influence
satellite design. Equally important is the use of autonomy (in orbit, support,
etc.) in sate!!!te development and operation to permit a better product at a reduced
cost.
Finally, the industry/government steering committee indicated the need for
validating technology using terrestrial and/or In-space testbeds. This would
include space act agreements covering the use of government-owned testbeds and
Judicious in-space testing as absolutely necessary.
The steering committee support for this new initiative has been outstanding
and enthusiastic. All participants have shown a keen desire to create a new mode
of operation that will enable the prompt introduction of new technologies and new
ways of building and operating future spacecraft.
335
IHE WORKSHOP
As part of developing the Spacecraft 2000 initiative, a workshop was held July
29-31, 1986 in Cleveland, Ohio. The objectives of the workshop were to identify
the critical needs and technologies for spacecraft of the 21st century and to recom-
mend technology development/validatlon programs and possible government/industry
roles and partnerships. Forty-two organizations from both government and industry
participated in the workshop. As a common base, plenary sessions delineating space-
craft needs and trends and outllng the expected space infrastructure for the year
2000 were presented. Nine working group sessions covering all critical spacecraft
bus technologies and systems were conducted. Each group was cochalred by industry
and government representatives. In each of these working group sessions, critical
technologies were identified. It was evident from the output of the groups that a
bridge is required for new technologies to reach flight readiness. The need for
government-sponsored terrestrial and/or In-space test beds for technology validation
was also emphasized in each of the reports. During the course of the workshop, the
steering committee also deliberated on government/Industry relations to find common
ground and a satisfactory approach for the program. Enthusiastic industry and
government support for the Spacecraft 2000 program was evident. This workshop
represents the first step in establishing the foundation for a new initiative to
assure the broadband advocacy by all participants and to define a new partnership
between government and industry that will lead to future enhancement of the space-
craft industry.
CONCLUSIONS
It is clear that the potential exists for major gains to be made in spacecraft
of the 21st century. Specifically, the mass fraction of the payload could be
doubled through substantial reductions in the bus mass fraction. This can be
accomplished along with significant reductions in cost and increases in lifetime
and reliability. Additional advances are anticipated in manufacturabillty, testing,
servicing, and supportability. These benefits apply to all spacecraft (NASA, DOD,
and commercial) and to areas such as communications, Earth observation, navigation,
rescue, air traffic control, etc. The resulting cost reductions and performance
improvements of this program will enable new cost-effectlve missions and allow
enhanced competitiveness in world markets and with terrestrial alternatives.
A NASA/DOD/industry steering committee is intent on forging a new government/-
industry relationship that results in benefit to both and minimizes the liabilities.
The hope is to create in the space business a government/Industry relationship
similar to that found in the aeronautical business. The challenge (and the vision)
is to construct a program that allows individual organizations to develop and vall-
date critical technologies by judiciously using government, IRAD, and some corporate
funds and to maintain their proprietary rights thus enhancing both their intraand
international competitiveness. All parties can win, and the world can benefit from
the successful conduct of this program.
Support for this new NASA initiative, Spacecraft 2000, is growing in industry
and in government. The next year will be important, as the 1986 workshop will pro-
vide the technological foundation and the basis for government/industry relation-
ships. The multifaceted advocacy can then be undertaken that could result in a new
initiative as early as 1989.
336
Webelieve the Spacecraft 2000 initiative addresses the major needs and tech-
nological drivers for the spacecraft of the 21st century. Weall must work together
to bring this vision of the future into being for the national best interest.
337
SPACECRAFT BUS TECHNOLOGY
TOTAL SPACECRAFT MASS
STRUCTURE ATTITUDE
b CONTROL
THERMAL TT_C
2oi ]o;-
f CURRENT PAYLOAD
to MASS FRACTION
CURRENT X
IV V VI SATCOM
,,,_,?.,,,_,,,,,,,,
FLTSATCOM
Figure 1.
INTELSAT SATELLITE UTILIZATION CHARGE
7O
6O
50
2O
10
e5 06 71 T2 73 7'4 7'5 7'6 77 T8 7'9 80 81 82 83*
?0
CALENDAR YEAR
8
Projected
Figure 2.
338
SPACECRAFT 2000 INDUSTRY VISITATIONS
GENERAL ELECTRIC
FAIRCHILD CORPORATION
FORD AEROSPACE CORPORATION
LOCKHEED MISSILES AND SPACE CORPORATION
TRW INCORPORATED
ROCKWELL INCORPORATED
HUGHES AEROSPACE CORPORATION
RCA ASTRO DIVISION
COMSAT CORPORATION
Figure ,
ADVANCED TECHNOLOGY FOR
GEO POWER SYSTEMS
l0
40
30
POWER TO
(lEO (kW|
2o
"t
o
IUS
B
HHIIIIIIII
,,,o I
....umlll
Wf/////////,
STS/CENTAUR
(_ leJlm no Rmtlmll4Je4_
Figure .
339
ADVANCED GEO POWER SYSTEM TECHNOLOGY
400 I
300 w
MASS
(kg)
200 -
lOO -
o
PRESENT
(7.2 W/kg)
TDRS
DC WIRING
HARNESS
BATrERY
SOLAR
ARRAY
2600 W BOL
FUTURE
(50 W/kg)
PGU
f 50 I_t SILICON CELL
ARRAY
/ HIGH VOLTAGE
GRAPHITEf
_/ HARNESS
PCU"-_ "-- i / BATTERY
I i _"SOLARARRAY
II_IA NQ lira t_ll4lPm
Figure 5.
EUROPEAN SOLAR ARRAY TECHNOLOGY
EOL
POWER
KW
6
2
0
IJIlJRANG E
1004)
_$_ " _,R_LSA T)
_ O ARA ILSA
.,,- "" 8POT
I I I I I -
1980 1985 1990 1995 2000
YEAR
Figure 6.
340
SPACECRAFT BUS VOLTAGE
BUS
VOLTAGE
V
60 _,'"_ EUROPE
40 _AT
20 _USA
1966 1974 1982 Figure
.
ELECTRIC PROPULSION PROGRAMS
U,S.
| I ! i i i | • a i t ! i i t i i i i I I I
_/ Funded effort "/z//i,/'z/z/,,/,/'.,///./'./'./'/1/1./'./',/'./'//7"//_/_
_. Flights Z_ A _"
USSR _
_ Europe
Japan ZI
)
! I f
65 70 75
YEAR
8O
A
Figure .
341


Spacecraft 2000: The challenge of the future

Abstract

Similar works

Full text

Available Versions

NASA Technical Reports Server