Reentry communication by injection of water droplets into plasma layer surrounding space vehicl

Nelson, C. H.

English

NASA Technical Reports Server

REPLY TO 
ATTN OF: @p 
NATIONAL AERONAUTICS AND SPACE AD 
WASHINGTON, D.C. 20546 
October 15, 1970 
TO : USI/Scientific & Technical Information Division 
Attention: Miss Winnie M. Morgan 
FROM: GP/Office of Assistant General 
Counsel for Patent Matters 
SUBJECT: Announcement of NASA-Owned 
U.S, Patents in STAR 
In accordance with  the procedures contained in the Code GP 
to Code US1 memorandum on this subject, dated June 8, 1970, 
the attached NASA-owned U , S ,  patent is being forwarded for 
abstracting and announcement in NASA STAR, 
The following information is provided:: 
U,S. Patent No, : 3,277,375 
Corporate Source 
Supplementary 
Corporate Source 
NASA Patent Case No,: XLA-01552 
Gayle Parker 
Enclosure: 
Copy of Patent c( 0 
9 
5 
9 
NASA-HQ 
https://ntrs.nasa.gov/search.jsp?R=19710001809 2020-03-17T02:35:52+00:00Z
REENTRY COMMUNICATION BY MATERIAL ADDITION 
Filed Dec. 19, 1963 
2 
28 
BY 
RJVmvTQRd 
CLIFFORD H. NELSQN 
19, B963, Ser. NQ. 332,339 
2 GBaims. (CI. 325-653 
The invention described herein may be manufactured 
and used by or  for the Government of the United States of 
America for governmental purposes without the payment 
of any royalties thereon or therefor. 
This invention relates to radio-frequency communica- 
tion to and from a space vehicle and more pafiticularly 
concerns a method and apparatus for accomplishing radio- 
frequency communication through the plasma formed 
around a space vehicb: as it enters or leaves a planetary 
atmosphere. 
Whenever a space vehicle traveling at a hypersonic 
speed (Mach 10 or above) enters or Ieaves a planetary 
atmosphere, it is surrounded by a shock-induced layer of 
ionized gases. This energized layer of gases or plasma 
prevents radio-frequency signals from passing through it. 
The radio-frequency signals are either reflected or  ab- 
sorbed by the plasma. Consequently, radio-frequency 
communication to and from the space vehicle is either 
partially o r  totally obstructed during the times that the 
space vehicle is surrounded by a layer of plasma. Since 
a layer of plasma is formed around a vehicle during critical 
phases of its flights (while leaving and entering a plane- 
tary atmosphere), it is desirable to be able tQ communi- 
cate through the plasma. 
In the past, there have been several schemes suggested 
for accomplishing radio-frequency communication through 
the layer of plasma surrounding a space vehicle while it is 
reentering the earth's atmosphere. Among these schemes, 
is the scheme of selecting for use a signal frequency that 
will penetrate or pass through the hypersonically gener- 
ated plasma. Extremely high or very low radio fre- 
quencies will pass through the plasma. However, since 
most communication equipment presently in use is de- 
signed for the VHF-UHF bands (30 mc. to 300 mc. and 
300 mc. to 3,000 mc.) there is an equipment acquisition 
problem if either the extremely high or very low fre- 
quencies is used. Also, at  the higher frequencies there is 
an atmospheric absorption problem and at the lower fre- 
quencies there are atmospheric noise and antenna prob- 
lems. 
Another scheme which has been suggested consists of 
altering the electromagnetic properties of the plasma by 
superimposing a static magnetic field. However, this 
scheme has a disadvantage in that it requires large mag- 
netic4ield producing systems for large space vehicles. 
The present invention is concerned with injecting a ma- 
terial into the flow field of the plasma to open a hole in 
the plasma layer through which radio-frequency signals 
can he transmitted. This hole is produced by reducing 
the electron concentration of the plasma. The possible 
ways in which the material reduces the electron concen- 
tration is by cooling the plasma: by increasing the recom- 
bination rate of electrons and ions in the plasma; and by 
the attachment of electrons in the plasma to the injected 
material. 
When a material such as gas is ejected at the surface 
of a space vehicle, the gas causes a great disturbance to 
the plasma flow field and instead of mixing tends to cause 
the flow field to bulge around the ejection site. Because 
of this bulging, a hole is not opened through the plasma 
and the surface of the layer of plasma is made larger. 
Therefore, it is desirable to use a material that can be 
distributed into the plasma flow field with minimum fiow 
fleld disturbances. It has been found that liquid drm@pbts 
are good materials for this use. Also, in the Use Of li~r.ia', 
droplets evaporation and heat transfer can occm b &o 
5 short residence time of the coolant in the vehicle vicinity. 
Water is a good liquid to use because it has a high heat 
capacity both as a liquid and a vapor and it has a 
latent heat of vaporation. Water also increases tka r t a  
combination rate, and has an affinity for electrons. 
I t  is therefore an  object of this invention to provide 
a method and apparatus for enabling radio-frequency 
communication through the layer of plasma formed am& 
a space vehicle as it either leaves or enters a planetary 
atmosphere. 
Another object of this invention is to provide a, netbcd 
and apparatus for injecting a material into the plasma %PY 
field formed around a space vehicle while it is either h v -  
ing or entering a planetary atmosphere to accomplish 
radio-frequency communication through the plasma. 
A further object of this invention is to provide a meth- 
od and apparatus for injecting liquid droplets into the 
plasma flow field formed around a space 
it is either leaving or entering a planetary 
accomplish radio-frequency communication throua the 
Other objects and advantages of this invention fur- 
ther become apparent hereinafter and in the drawings; & 
which: 
FIG. 1 shows a schematic diagram of a space vehicb 
30 and the apparatus that constitutes a preferred embodiment 
of this invention; 
ETG. 2 shows a more detailed schematic diagram of the 
apparatus that constitutes a preferred embodiment of this 
invention; and 
PIG. 3 shows an enlarged end view of a nozzle 
shown in FIG. 2. 
In describing the preferred embodiment of the inven- 
tion illustrated in the drawings, specific terminology will 
be resorted to for the sake of clarity. However, it is n 
40 intended to be limited to the specific terms so selected, an 
it is to be understood that each specific term includes 
all technical equivalents which operate in a similar man- 
ner to accomplish a similar purpose. 
Turning now to the specific mbodirment of the inven- 
45 tion selected for illustration in the dmwings, the number 
1% designated generally a space vehicle with an antenna 
12 attached to the outside srface thereof. B l e c t r i d y  
connected to antenna I2 is communication equipment 1 
This communication equipment consists of a tmns&ter 
50 and a receiver. When space vehicle 12 is entering or 
leaving a planetary atmosphere o layer of plasma d 
formed around the vehicle which prohibits the vehicle 
from communicating with a remote sbation I§. R e d *  
station 1s consists of a transmitter, a receiver and an 
58 antenna. A water supply 16 which is under pressure is 
connected to sites 17 and 18 on the outside s u r f m  
vehicle 111 by a tube 19 to spray water into the layer of 
plasma 14. This 0 in the, 
10 
15 
20 
25 plasma. 
35 
plasma 14 enabl tfJ P W  
00 between vehicle Thus, ' 
radio- frequency .bt.weenr * 
space vehicle $4 and remote station 15. Site 37 can k 
located (anywhere on the side of vehicle 11 and the=  cat^ 
be any desired number Olf these sites. Site 18 is located 
65 in the stagnation region and there can be any desired' 
number of these sites. The stagnation region is that por4 
tion of the layer of plasma immediately adjacent to &e 
vehicle's leading edge. The stagnation region ha5 been 
70 proven to be the most effective s i b  to spray 
the plasma on long slender space Wcks. 
it is doubtful that this will be true for blunt-nosed ye& 
des--too much water might >e required. Much more 
watcr is nceded for a stagnation region spray than for a 
side spray because a stagnation region spray tends to 
eliminate the whole layer of plasma whereas a side spray 
tends to open only a hole in the layer of plasma. 
Referring now to FIG. 2, there is s h m h  in more detail 
the apparatus used to spray water into the plasma around 
the space vehicle 11. A tank 16 is divided into two 
compartments 22 and 23 by a diapnram 26. Compart- 
m n t  22 is filled with water and compartment 23 is filled 
with N2. The Nz in compartment 23 is under pressure 
which pressure is exerted against diaphragm 24 putting 
the water in compamtment 22 under pressure. Tube 19 
connects compartment 22 to a manifold 26. Located in 
tube 19 is a valve 25. Valve 25 can be hand operated 
or it can be automatically operated lby a preprograuned 
control. It can also be hand operated or preprogramed 
to turn “on” and “off’ for shont intervals of time to con- 
serve the water supply. Any desired number of tubes 
27 connect manifold 26 to nozzles 28. Located in each 
tube 27 is a valve 29. Valves 29 can be band operated 
or they can be automatically operated by a prepro- 
gramd control. All or any number of the valves 29 
could be turned on at any given time. Any number of 
nozzles 28 can be located $at sites 17 and 18 or at any 
other desired site on the outer surface of space vehicle 11. 
Referring to FIG. 3, there is shown an end view of a 
nozzle 28. Each of the nozzles 25 has several orifices 38 
in it through which water wiH pass. The number and 
size of these orifices can be different Eor each nozzle 28, 
depending on where tthe nozzle is to be located. For 
injection from the stagnation site 18, up to seven 0.080- 
inch-diameter orifices 30 have been used with success; 
and for injection from the side site 17 up to ninetyeight 
0.015-inch-diameter per side have been used with success. 
Two side sites on opposite sides of vehicle 111 were used. 
The sizes of orifices 30 can be different than the specific 
sizes mentioned above. The sizes of the orifices depend 
on the ejection site, the anknna location and the size and 
shape of the space vehicle. It is necessary only that the 
orifices are small enough so that the water droplets ejected 
therefram will vaporize before they leave the vehicle 
vicinity and will penetrate the plasma without bulging it. 
The amount of water ejected by orifices 38 will depend 
on the injeotion site and on the size and shape of the 
vehicle. For a vehicle having an eight-inch diameter 
nose, a velocity of approximately 17,800 ft./sec., and oper- 
ating in the altitude range of 1G0,OCO to 250,000 ft., water 
flow rates of 0.3 to 00.1 pound per second have been 
proven to be adequate to relieve plasma $attenuation. 
These values were the lowest flow rates tested and even 
lower values may be effective. For larger vehicles and 
higher velocities, somewhat larger amounts may be 
needed. The amount of water used can be vaned by 
opening different combinations of values 29, or by vary- 
ing the pressure of N2 in compartment 23. 
The operation of the apparatus which constitute the 
preferred embodiment of this invention will be described 
while referring to FIGS. 1 and 2. Whenever space ve- 
hicle 11 is either entering or  leaving a planetary atmos- 
phere, a layer of plasma 14 is formed around the space 
vehicle which prohibits radio-frequency communication 
between the space vehicle and a remote station 15. To 
alleviate this problem, the pilot or an automatic control 
opens valve 25 and any desired number of valves 29. 
The water in Compartment 22 of tank 16 is then forced 
through tube 19 by the N2 in compartment 23. The 
water is sprayed out through orifices 30 into the layer of 
plasma 14, opening up a hole 20 therein. Now radio- 
frequency communication can be maintained between 
space vehicle 11 and remote station 15 through hole 20. 
It is necessary only to vary the number of valves 29 that 
are open to vary the amount of water sprayed into the 
plasma. Water can be conserved by opening and closing 
4 
valve 25 for short intervals of time to produce pulses &E 
water out of orifices 30. 
The advantages of this invention are numerous. It al- 
lows the use of standard communication and telemetry 
5 gear on board a space vehicle during the times that it is 
leaving or entering a planetary atmosphere. It consists 
of equipment that is relatively simple and inexpensive 
and thzt can be installed on existing missiles and space- 
craft. And it can utilize the excess water during reentry 
from fuel cells, waste, and surplus water supply that 
might be aboard the space vehicle. 
It is to be understood that the form of the invention 
herewith shown and described is to be taken as a preferred 
embodiment. Various changes may be made in the 
15 shape, size and arrangement of parts. For example, 
equivalent elements may be substituted for those illus- 
trated and described herein, parts ,may be reversed, and 
certain features of the invention may be utilized inde- 
pendently of the use of other features, all without depart- 
20 ing from the spirit or scope of the invention as defined in 
the subjoined claims. The invention could be used on a 
passive communication satellite, thereby eliminating the 
need for communication equipment on board the space 
vehicle. The invention uses water as a means of cool- 
25 ing and modifying the plasma. Freon 12 (CClzFZ) has 
also been used and found to be effective. Other liquids 
. or solids might also be used. In particular, liquids or 
solids with large latent heats and/or heat capacities such 
as liquid hydrogen and ice would be possible materials. 
30 Accordingly, it is to be understood that the term liquid 
as used in the subjoined claims is not necessarily re- 
stricted to water and the term nongaseous substances in- 
cludes both liquids and solids. 
What is claimed as new and desired to be secured by 
35 Letters Patent of the United States is: 
1. Apparatus for accomplishing radio-frequency com- 
munication between a space vehicle and a remote station 
during the times that the space vehicle is surrounded by 
a layer of plasma comprising: communication equipment 
40 located on board said space vehicle and at said remote 
station; a liquid supply located on board said space ve- 
hicle; and ,means located on said space vehicle for spray- 
ing small droplets of said liquid into said layer of plasma 
whereby substantial evaporation of the liquid and heat 
45 transfer between the liquid and the plasma occurs in the 
short residence time of the liquid in the vehicle vicinity 
2nd substantial numbers of electrons in said plasma at- 
tach to said liquid droplets thereby reducing the electron 
concentration of said layer of plasma to enable radio-fre- 
50 quency communication between said space vehicle and 
said remote station. 
2. A method for altering the layer of plasma formed 
around a space vehicle while it is either entering or leav- 
ing a planetary atmosphere so that radio-frequency com- 
55 munication can be made through the layer of plasma c o ~  
prising: the steps of providing a liquid supply on board 
said space vehicle; and spraying small droplets of said 
liquid into said layer of plasma whereby substantial evapo- 
ration of the liquid and heat transfer between the Iiquid 
GO and the plasma occurs in the short residence time of the 
liquid in the vehicle vicinity and substantial numbers of 
electrons in said plasma attach to said liquid droplets 
thereby reducing the electron concentration of said layer 
of plasma to enable radio-frequency communication 
eferenees Cited by the E x ~ ~ ~ e ~  
UNITED STATES PATENTS 
3,128,965 411964 Ziemer ----_------ 343-100 X 
05 through said layer of plasma. 
70 
DAVID G. REDINBAUGH, Printmy Examfner. 
LEWIS H. MYERS, Examiner. 
R. E. BERGER, J. W. CALDWELL, 
75 Assistant Examiners. 


Reentry communication by material addition Patent

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