A set of questions is posed regarding the surface chemistry producing the ram glow on the space shuttle. The questions surround verification of the chemical cycle involved in the physical processes leading to the glow. The questions, and a matrix of measurements required for most answers, are presented. The measurements include knowledge of the flux composition to and from a ram surface as well as spectroscopic signatures from the U to visible to IR. A pallet set of experiments proposed to accomplish the measurements is discussed. An interim experiment involving an available infrared instrument to be operated from the shuttle Orbiter cabin is also be discussed

Mende, S. B.

Swenson, G. R.

English

NASA Technical Reports Server

DATA REQUIREMENTS FOR VERIFICATION OF RAM GLOW CHEMISTRY 
Gary Swenson and Steve Mende 
Lockheed Palo Alto Research Laboratory 
Abstract. 
surface chemistry producing the ram glow on the space shuttle. The 
questions surround verification of the chemical cycle involved in the 
physical processes leading to the glow. The questions, and a matrix of 
measurements required for most answers, are presented. The measurements 
include knowledge of the flux composition to and from a ram surface as 
well as spectroscopic signatures from the UV-visible-IR. A pallet set of 
experiments proposed to accomplish the measurements will be discussed. 
An interim experiment involving an available infrared instrument to be 
operated from the shuttle Orbiter cabin will also be discussed. 
A set of eleven questions has been posed regarding the 
Introduction 
Several papers in this report address the surface chemistry involved 
in production of the "red" ram glow associated with the space shuttle. 
Questions to Address-Surface Ram Glow 
1. 
2 .  
3 .  
4. 
5. 
6. 
7 .  
8. 
9. 
10. 
11. 
The following is a set of questions that we have assembled which are 
aimed at further understanding and quantifying the glow processes. This 
set of questions is a general set that needs answers to further clarify 
and quantify the physical processes involved. First we address a set of 
questions for glow from a given material: 
How does NO material exit flux relate to the NO continuum glow on the material? 2 
How does NO material exit flux relate to NO beta, delta, and/or 
gamma band emission? 
How does the NO2 continuum glow extend into the infra ed? Does it 
continue to drop as we observe between 7000 and 8000 8? 
Is the NO "fine structure" superimposed on the continuum as it is 
in the lagoratory spectrum? 
Is there a component of N2 lPG, and if s o ,  how does it extend into 
the IR? 
Howodoes 1-5 vary with material temperature (between -250' and 
400 K)? 
How does 1-5 vary with NI and 01 flux from the atmosphere? (i.e., 
How can we expect the glow to vary with altitude?) 
How does 1-5 vary with ram angle to the sample surface? 
Does O2 become a production factor at low altitude as implied by 
the AE-C data? 
How do different material surfaces influence 1-9 above? 
How does the chemistry become enhanced/quenched with controlled 
injection of NO and other gases? 
260 
https://ntrs.nasa.gov/search.jsp?R=19860003797 2020-03-20T15:57:10+00:00Z
This set of questions addresses process verification and 
quantification for temperature and materials. The experimental approach 
is outlined below as to how many of these questions can be addressed. 
Technical Approach-Experimental Method 
The all-up matrix approach with the pallet instruments yields the 
ultimate in answers to the questions regarding 
but there are some intermediate experiments that can be assembled 
quickly which can answer some very important questions. 
fabricated and is available as a candidate instrument to observe the IR 
component of glow from the Orbiter cabin. The aft flight deck window has 
reasonable transmission between 1.2 and 2.4 microns (-40%-variable). 
Figure 1 shows a mechanical configuration of the instrument, and Table 1 
is a summary of.the optical characteristics. 
the questions addressed above. This constitutes operating a set of 
instruments in the space shuttle bay which would monitor the flux of 
molecules impinging on and emanating from a surface in ram. At the same 
time, observations of the glow on the surface would be monitored in the 
UV, visible, and IR wavelengths. A glow mission would require a few 
orbits of dedicated attitude to perform the glow studies, at low-Earth 
orbit (-250 km). The instruments would be preprogramed to perform the 
experiment sequences during the glow attitudes. We have structured a set 
of instruments which can provide significant information on the 
processes. Some of the questions posed would require a quality, 
high-resolution visible spectrometer, as well as a high-resolution 
cryogenic IR instrument. In the spirit of "a step at a time" and low 
cost, we have structured an essential set of pallet instruments which 
can provide many importan 
desirable for follow-up studies as we now understand the chemistry. A 
basic set of experiments without these refinements is described herein. 
The instruments we envision include a sample surface plate (-1 meter 
x 1 meter) which would be positioned in the pallet in such a way that 
the ram atmosphere could be directed towards it. An optical sensing 
stand would view the plate from nearly edge-on to take advantage of the 
near surface brightness emanating from the plate surface. The plate 
would bg tipped up, and a mass spectrometer would view the plate from 
near 45 to plate normal. This set of Instruments would constitute the 
main glow package (see Figure 2). 
The plate would be coated with one material and on subsequent mission 
opportunities, other materials would be studied. The plate would ideally 
have provision for heatgng electrically so the plate temperature could 
be elevated t o  near 400 K. It is possible to make a plate which could 
rotate to subject two-three different surfaces to ram during a mission, 
but our initial consideration is to have a single surface. The plate 
would contain a baffle on the down viewing side of the optical package, 
such that a black background would be provided to the glow viewing 
instrument s o  
The optical package will include three instruments which will 
document glow from the UV to the IR. The instruments are summarized in 
Table 2. Instrument 1 will be an automated version of the hand-held 
physical processes, 
A portable CVF (Circular Variable Filter) instrument has been 
We herein describe a set of experiments which would answer many of 
answers to key processes. A high-resolution 
visible spectrometer (-1 8 resolution) and a cryogenic IR instrument are 
26 1 
instrument which has flown as a locker experiment in the orbiter. This 
instrument will operate in an imaging mode, as well as a spectrometer 
mode, to clarify the glow in the 4000-8000 8 wavelength region- This 
instrument will document the spatial distributions of the glow and 
provide the bridge of measurement to the early d 
will be the UV instrument to clarify NO band emi 
presently unknown UV emis 
between 2000 and 4000 2 
a UV imager bore-sighte 
spectrometer would scan 
spatial distributions of the UV glow. Instrument 3 will consist of a 
thermal, electrically cooled PbS detector to cover the IR wavelengths 
between 1 and 3+ microns. The IR shape of the NO2 continuum and possibly 
other glowing candidates would be measured with this instrument. 
entrance and exit flux of NI, 01, NO, and NO 
is essential to document the constituent phenomena associated with the 
chemical processes. The instrument herein is one very different from the 
AE instrument in that the requirement is to make the measurement of 
ambient NO and NO2 emanating from the plate, In order to accomplish 
this, the instrument must be of a type where the molecules are ionized 
external to an instrument orifice before any wall collisions have 
occurred. Next, this produced beam would be focused and mass-analyzed as 
in a conventional mass spectrometer. The instrument would be an 
orifice-pumped instrument with a mechanical flag in the orifice. The 
pumping is necessary to minimize orifice collisions in the high-density 
shuttle environment. The mechanical flag allows a degree of direction 
control of the sampling beam. The flag would alternately direct 
molecules from a surface sample plate and from the atmosphere to be 
sampled by the instrument. 
all essential to a basic pallet payload. A matrix of problems versus 
instruments has been produced (see Table 3 ) .  For most of the questions 
at hand, several instruments are desired. Model atmospheres can be used 
with some reliability for the atmospheric flux to the spacecraft, but 
the measurement with the mass spectrometer is best. Only the mass 
spectrometer can resolve what is coming off the plate in the way of mass 
species. 
We are also giving consideration to gas release cannisters which, 
when released, would be located such that the drift cloud would pass 
over the plate- It has been noted that the thruster effluent acts to 
enhance the stand-off ram glow significantly for several seconds when 
impinging on a ram Orbiter surface. The thruster gas consists of 
significant amounts of NO, which we believe adds to the surface 
monolayer of NO. This additional source of NO seems to deplete in lees 
than 1 minute in ram. Gas cannisters with NO and other gases which in 
fact would act to quench the process would be considered. The gas 
cannisters could be relatively small in size and of the single release 
type 
We suggest that the "shuttle hitchhiker" concept be a candidate 
facility within which experiments could be structured. The "hitchhiker" 
offers a simple interface and minimal delivery time before mission 
execution. At the same time, it appears to offer command and data 
handling capabilities which are adequate for the required measurements. 
set. Instrument 2 
on (as well as any 
ns). Filters for the known NO band emissions 
ter spectrometer. The 
e the imager documents the 
A mass spectrometer of the type which is designed to examine the 
from the surface plate 
will be located separately from the optical 1 nstruments. This instrument 
The above surface plate, optical cannister, and mass spectrometer are 
262 
Summary 
There are a number of questions which need to be ans 
understand the physical and chemical processes involved 
basic questions are scientifically important to underst 
interaction of the atmosphere with the fast moving spac 
questions are well suited to be explored with well known, 
state-of-the-art instrumentation which can be implemented into a shuttle 
pallet payload for experiment implementation. the exciting results will 
be scientifically interesting in themselves since low-energy neutral 
beams of 5-10 eV are difficult to implement in the laboratory with 
significant flux levels. The experiments will also yield useful 
information regarding potential background contamination for planned and 
future experiments. Through understanding the physical processes, we can 
understand how to engineer our instrumentation and plan our operations 
of space optical instrumentation with minimal signal degradation. 
263 
264 
PALLET GLOW INSTRUMENTS 
(TOP VIEW) 
NOZ,  NO 
Fig. 2. A schematic representing the pallet-based instruments viewing 
molecules and glow emanating from a sample surface. 
265 
TABLE 1. OPTICAL CHARACTERISTICS OF THE CVF SPECTROPHOTOMETER 
PORTABLE INFRARED SPECTROPHOTOMETER [CVF] 
* FIELD-OF-VIEW - 2 degress (full) 
* WAVELENGTH RESOLUTION - Bandwidth (3% tuned wavelength 
* SPECTRAL RANGE - 1.3 to 3.2 microns per scan + shutter 
[reasonable aft window transmission 1.2-2.4 microns] 
- Broadband mode - use SC window as filter 
* SENSITIVITY - 80 Rayleighs/Angstrom for 1-second integration 
[detector = 4 X 4 m, PbS, TE cooled to <200 kelvin] 
* POWER - -17 watts (measured) 
* VOLUME - Optical system:L = 35 cm, Width = 12.5 cm 
Electronics: L = 20 cm, Width = 20 cm, Ht.= 20 cm 
* DATA AND CONTROL - TRS 80 + recorder 
266 
TABLE 2. A SlJMMARY OF A CANDIDATE SET OF PALLET INSTRUMENTS SUITABLE 
FOR STUDY OF SPACECRAFT RAM GLOW 
PALLET GLOW INSTRUMENTATION 
81 
I/ 2 
# 3 
#4 
RED BROADBAND IMAGING SPECTROPHOTOMETER 
* 20 degree FOV 
* 4000-8000 Angstroms 
* Resolution 30 Angstroms 
* Imaging or spectrometer mode 
UV BROADBAND IMAGING SPECTROPHOTOMETER 
* 20 degree FOV 
* 2000-4000 Angstroms 
* Resolution 30 Angstroms 
* Imaging and spectrometer mode 
IR CVF SPECTROPHOTOMETER 
* 2degrees FOV 
* Spectral range 0.8-3.0 microns 
* Resolution 3% 
MASS SPECTROMETER (OPEN SOURCE) 
* 2 degrees FOV 
* Flag directed beam (10 degree deflection) 
(monitor source flux and background) 
* Pumped orifice 
267 
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268 


Data requirements for verification of ram glow chemistry

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