Possible configurations of space vehicles which would be delivered to Venus by rocket system in order to autonomously carry out flights in an automatic (and possibly piloted) mode are considered with respect to mission and flight altitude. Base (high altitude) vehicles, operating at pressure, sendity, and temperature corresponding to those on Earth at sea level, will have little maneuverability, will serve as carriers for equipment, scientific devices, and other cargo, and will study the gas composition of the Venus atmosphere from above. Low altitude vehicles will explore the planet from flight altitude in the vicinity of the planet's surface, as well as land on it. Analogous to deep submergence vehicles such as the bathyscaphe and the bathyplane, they will have a certain amount of maneuverability and will study the atmospheric boundary layer from below. The advantages of aerostats in this environment are discussed. Drawings of the aerostatic base station, the variable-length aerostatic sing vehicle, and the hybrid aerostatic vehicle with attached wings are included

Moskalenko, G. M.

English

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SPACECRAFT FOR FLIGHT IN THE ATMOSPHERE OF
VENUS
NASA TB. Mffi^ORANDUH
	
NASA TM-75932
G. M. Moskalenko
(tillSL-ZlS-75932) SPaCECS1^FT POR FLIGHT IN	 N80-17134
THE AT!lOSPHERE OF 9ENIIS (rational
Aeronaatics and Space Administration) 13 p
8C A02/HF A01	 CSCL 22B	 I)nclas
GS/ 18 12 86 8
Translation of Zemlya i Vselennaya, No. 4, July-August
1979, pp 21-26
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NATIONAL AERONAUTICS AND SPACE ADMINISTRATION
WASHINGTON, D. C. 20546
	 FEBRUARY 1980
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SPACECRAFT FOR FLIGHT IN THE ATMOSPHERE OF VENUS
Moscow ZEMLYA I VSELENNAYA in Russian No 4, Jul--Aug 79 pp 21-26
[Article by candidate of technical sciences G. M. Moskalenko]
[Texts Vehicles able to fly in the atmosphere of Venus
will be required in the further exploration of that
planet. What will ti^^y look like?
Direct spacecraft exploration of Venus was begun in October, 1967, by the
Soviet Venera-4 automatic station. After reaching the planet, it made the
fir^*.-ever smooth descent into the planet's atmosphere down to an altitude
of 2ti km above its surface; the station transmitted for 1.5 hours data on
the physical, chemical, and structural parameters of the atmosphere. In
May, 1969, Veneras-5 and -6 penetrated to 20 ktn above the surface. Then a
qualitatively new level in the exploration of Venus was achieved in Decem-
ber, 1970. The descent vehicle of the Venera-7 station landed and trans-
mitted information from the planets surface. On 22 July 1972, the descent
vehicle of the Venera-8 achieved soft landing on the planet's surface. The
exploration o£ Venus continued, and in October, 1975, the orbiting sections
of the Veneras-9 and -10 stations were injected into near-planetary orbits;
thus, for the first time, artificial satellites of the planet were created
and television images of the surface obtained from the descent vehicles.
The study of Venus was continued by the Soviet Venera-11 and Venera-12 sta-
tions and by the American Pioneer Venus-1 and Pioneer Venus-2.
We already know much about Venus, yet there is even more to be lear*^ed.
Nobody doubts the advisability of further explorations of the atmosphere
and of conditions on the planet itself. But how best to achieve that? In
order to answer this, serious development o£ possible vehicles .Ls necessary.
Such vehicles would be delivered to the planet by rocket systems; they would
then autonomously carry aut exploratory flights in an automatic (and pos-
sibly even piloted mode.
1
Flight Conditions
And so, what could be used for flight in the Venusian abgosphere? The ques-
tion is complicated. The problelq is that the density of the Venusian atmos-
phere is about 55 times greater than Eartb.'s, and its pressure corresponds to
the pressure in an earthly sea at a depth of about 1 km. Therefore, a Venu-
sian flight vehicle has to incorporate a system of complex flight^aechanical
properties appropriate simultaneously to aviation, lighter than-air flight,
and deep submergence equipment and yet capable of withstanding high tempera-
tures at the same time.
Difficulties occur also in creating a powerplant, as no atmospheric oxygen is
available for its operation as it is on earth. The atmosphere of Venus con-
sists of 96 percent carbon dioxide, 4 percent nitrogen, and practically no
oxygen. The usefulness of solar batteries under the conditions of high den-
sity and low light transmissibility in the Venusian atmosphere is also dubi-
ous.
Aerodynamic loads, aerostatic forces, heating of the structure, type of pro-
pulsion, and other characteristics of the flight vehicle depend substantially
on the properties of the atmosphere. The value of all aerodynamic charac*er-
istics and the type of flow about bodies are determined by the Reynolds num-
ber. This number indicates the role played by the forces of viscosity in the
motion of a vehicle through a resisting medium. Tf it is large, viscosity
can be neglected; when small, it has to be considered. The following ques-
tion arises: Is it possible to use "earthly" aerodynamic coef^icients for
the computation of flight conditions in the Venusian atmosphere without intro-
ducing appropriate corrections for the value of the Reynolds number? Special
studies made by the author indicate that the Reynolds number for terrestrial
and Venusian atmospheres for similar flight profiles is relatively close and
therefore it is possible to make studies using terrestrial aerodynamic char-
acteristics of flight vehicles.
Venus Flight Vehicles
Depending on mission and altitude of flight, it is possible to group the Venus
flight vehicles into two categories: Base (high altitude) and deep [low alti-
tude] vehicles.
The high-altitude vehicles are intended for long-duration exploration in the
atmosphere using the drift mode (fiee^floating aerostat type) and for con-
trolled flight (dirigible type) at altitudes between 50 and 70 lan. Tn this
region, pressure, density, and temperature approximately correspond to those
on earth at sea level. The vehicles possess little maneuverability and serve
as carriers for equipment, scientific devices, and other cargo. High-alti-
tude vehicles can become the means for studying the atmosphere of Venus (its
gas compositions from above. Tn this group, we can include free floating
aerostats, drifting platforms Csingle and coupled), highly maneuverable vehi-
cles with aerodynamic features, aerostatic wings of variable volume (length),
2
Figure 2. Aerostat
Figure 1. Classf„ficati,on of Venus Flight
'Vehicles
Key:
1. Venus flight vehicles
2. Base [high altitude]
3. Communication
4. Deep [ low altitude)
5. Free floating
6. Controlled
7. Returnable
8. Nonreturnable
9. Soaring
10. Cruising
BexepAaxcAAe
AlTaTlA^NMe
annapaTU ^ 1 1
LaDSoANanAaaagaaNe (al
6aaoawe
Ynpatarewwe	 CG l
Boaepawaewue	 `^)
CaAaxwe
Heaoaapawaewue	 Cal
napAwNe	 (9)
fny6ANxue
MoDwnue	 /^1
Figure 3. Vehicle With Aerodynamic Features
3
4RIt31NAL PAGE 1^
!1F PCy^R QUALRY
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^ ^^^(^} IIAATNO-nOCAApWIAA IIOAOG	 i
OAOWAANA
;AA fAAMNOCtNTNYI	 ^^
	
AATNTAA►MMA AnnAOAfOA
	 ^^'',
(^)
^\ ^ ^ Jl
LAAAON►I^^^
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/	 ^OXAOAA C
^N^oNMI
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WA
9
aiNNe Nopnycw
` "^	 MAATNNNOAMII f,NApATOp 7NlpfMM
t8)
Figure 4. Aerostatic Base Station
Ke;
1. Helipad	 S. High-pressure tanks
2. Runway [flight deck] 	 6. Plants
3. Laboratory, living, and 	 7. Gondola
	
service spaces	 8. Pendulum power generator
4. Propulsion units	 9. Gas containers
and vehicles of toroidal configuration. The latter can serve as carriers for
rocket systems that deliver Venusian containers to Earth with scientific
information, surface samplea^ and ampules of at^aoapheric gas.
Drifting flight v^^.icles of sufficiently large dimensions can be used as car-
riers o f small exploratory deyicea intended #or Bounding those layers of the
atmosphere unreachable for the high and loin-altitude vehicles.
4
^OAyMlt^M Xf OOA^N7RNM! XONCO^N
	 r 1,
Figure S. Vehicle in the Form of a Variable-Length Aerostatic Wing
Key:
1. Semirigid, movable outboard wing panels
2. Span
3. Wing chord
4. Section thickness
5. Wing center section
The mission of the low-altitude vehicles is the exploration of the planet
from flight altitudes in the vicinity of the surface of Venus, as well as to
land on it. Analogous to deep submergence vehicles of the type such as the
bat'^yscaph and bathyplane, they can have a certain amount of maneuverability
and become the means for studying the atmosphere of Venus (its boundary
layer) from below. Among the low-altitude vehicles are bathyscaphs, bathy-
planea, vehicles of variable geometry, aerostatic convertiplanes, and others.
The largest class (in terms of design, aerodynamic form, and dynamics of
flight) of Venus vehicles are the co^qununication flight vehicles. Similar to
terrestrial ones, they can be equipped Kith a propulsion unit (returnable)
or be without one (nonreturnable). Communication vehicles can sound various
layers of the Venusian atmosphere, reach the surface of the planet, effect
communication between high-altitude and low-altitude vehicles, maneuver, and
return (if it is a reusable system) to the base flight vehicle.
5
-rte
4)pO tTa TNVatNNll TOp 	 ANN NIM TlNb CZ'
..^
ytunoaNa ^^^)
(^a)
1.
^S)	 3 .
4.
5.
6.
Mot,. tiJ
Aerostatic torus
Propulsion unit
Powerplant
Gondola
Trail rope
Surface
Figure 6. Vehicle ^Tith Toroidal
Configuration
Key:
Ml1laMN)M pa[N,MTNN	 / 1)N yaoaa nogT.erNw wapoa	 ` J
BoreyraN noaeprNOtTb
CNnb^ONM011 nonyC^lpa
3
Figure 7. Low-High Altitude Aeroscaph
a) At the moment of deploy-
ment, b) Stowed configuration
Key:
1. Mechanism for deploying and
retracting the buoyance
spheres
2. Buoyancy gas
3. Concave surface of the bel-
lows-type Hemisphere
a
6
^^^
DltiNbiM
!i)
b
What Vehicle Ts Beat?
Tt turns out that aexos^tats carxy the largest payload, chile drifting, they
require neither a powerful onboard powerplant installation nor large fuel
`	 supplies. They are capable of long-duration exploration and are relatively
single in construction. Buch vehicles can be equipped with a trailing cable
from which are suspended instruments for vertical sounding of the atmosphere
as well as devices #or obtaining surface samples. The length of the cable
is easily increased, and compensation is made for cable loading by attaching
lifting spheres at intervals along the cable. By proper choice of dimension
for the lifting spheres, the cable can be raised above the aerostat carrying
it.
From the viewpoint of flight mechanics, there are no objections to the idea
of such a vehicle, and its construction can be completed entirely under ter-
restrial conditions. However, serious questions arise connected with the
control of such a system, its stability in flight, and its reliability.
-	 A combination of dirigible and aircraft is of particular interest. The lift-
- ing surfaces (wings) are advisable should it be possible to achieve speeds at
which aerodynamic lifting force compensates, with some margin, for the weight
of the lifting surfaces. Under terrestrial conditions, such a combination is
usually not advantageous, but on Venue the vehicle can have some advantages
such as a large payload capability and the ability to maneuver in space,
resulting in a decrease in the mass of the gas-containing system.
Obviously, use can be made of aerostatic disk-shaped planes. The form of
this vehicle will depend on the gressure of the medium and can change from a
disk shape to spherical or cylindrical. For a deep descent into the atmos-
phere, such a vehicle will be disk-shaped and, therefore, besides aerostatic,
will also have aerodynamic lift due to the flow about its shape, which gives
it maneuverability. With such a rigid-body vehicle, it is possible to
achieve long-range flight without need for a propulsive unit, by using glid-
ing and lift (such as in an aerostat) along a sawtooth trajectory.
It is, of course, desirable to use returnable flight vehicles. These are
vehicles such as aircraft, helicopters, helistats, and devices for vertical
ascent and landing, and many other hybrid devices. But high maneuverability,
flight in different regimes, and zones of operation require the blending of
contradictory conditions of flight mechanics and a host of complex flight-
mechanical parameters. The main difficulty is the creation of power (propul-
sion) installations capable of working without oxygen for a long time under
conditions of high temperature and pressure.
But, on the other hand, nonreturnable flight vehicles do not present such
problems in implementation, and they can be used, along with aerologica^ bal-
lons (to be dropped into the yenusian atmosphere) as small-scale, onboard
means of flight.
7
/tI i
(OnA011a ^I^ 1
Figure 10. Hybrid Aerostatic Vehicle With
Attached Wing
-	
_	
:.^
^aaOeMPW agWi« clplpi na Fa: Vl tnOn	 ^^^
tucott Apenma
Figure 8. Floating Bathyscaph
1. Gas-containing sphere at the design altitude of drift
i^^	 Figure 9. Comaunication (Multipurpose)
MOCTpIt«MM g TOVn«. aMlp^nn	
Flight Vehicle
^z^ may:
:TlMa
«" AeY	 1. Isotope power source
2. Propulsion system
3. Landing devices
4. Gondola
9Ca60VMW!
CTpONCiU
^a)
xey
6
But how should these flight yahicles be delivered from Earth to the atAps-
phere of Yenus?
Problem of Transportation
Obviously the greatest difficulties arise in delivering vehicles of rigid
construction. The prispe item that determines the dimension of payloads at
the present time is the maximum allowable diameter of the last stage of the
rocket launcher. Calculations show that a rocket launcher of about 6-meter
diameter can deliver to Venus a ridi^i aerostatic envelope vehicle, which, at
the surface of the planet, has a lifting capability of about 6 toss. At an
altitude of 15 km, its weight-lifting ability decreases to 3 tans, but this
is already quite small, if we keep in mind that the envelope of such a vehi-
cle with its sarvice module requires a lion's share of that mass. For this
reason, rocket launchers at this time are able to deliver to Venue only vehi-
cles with a soft envelope such as slightly maneuverable ones such as low-
altitude bathyscaphs.
One can attempt to use improved stages of launcher rockets (those that achieve
escape velocity) in the role of aerostatic means at the low-altitude layers
of the Venusian atmosphere. Such stages, once the spent motors and their sup-
port systems have been jettisoned and once they have passed through the dense
layers of the atmosphere, will become suspended in its lower layers at alti-
tudes where the force of buoyancy equals the force of gravity.
Analysis of the entry trajectory into the dense layer of the atn^sphere shows
that the hot and dense atmosphere of Venus is more favorable (from a heating
point of view) to the entry of space vehicles than is the atmosphere of Earth.
This is because: (1) The density of the atmosphere of Venus at the altitude
of entry is less than the density of the Earth's atmosphere; (2) The speed at
which a spacecraft enters the Venusian atmosphere from satellite orbit
(7.32 km/a) is less than the speed with which a spacecraft enters the atmos-
phere of the Earth (7.95 kmis). Therefore, for a sufficiently low loading
per unit of lifting surface (wing), the temperature of heating does not exceed
the temperature in the vicinity of the surface of Venus.
Hypersonic aerostatic flight vehicles are of interest in this connection, as
they can eater the Venusian atmosphere without a descent mechanism when they
are filled with gas (either partially or fully). Such Venus vehicles are
particularly advantageous, because the bulky, gaseous balloon system can be
jettisoned during the approach to Venus and does sot represent a ballast for
further movements.
Peculiarities of Flight in the Venusian Atmosphere
Studies of flight mechanics carried out by the author of this article show
that aerostatic force significantly influences the characteristics of Venus
flight vehicles. It increases the altitude of flight for steady speed, it
increases the rate of ascent but decreases the rate of descent for flight in
9
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4	 - - - - - -- ^ ^-	 -	 g - - - -	 -^ . _ - ^-- ^-^---- ^
Figure 11. Diagram of Entry Into the Planetary Atmosphere of Both a High-
Altitude and a Low-High Altitude Aerostatic Vehicle
Rey
1. Hypersonic entry region
2. Descent region
3. Cruising flight
4. Descent (ascent) region of the low-high altitude vehicle
5. Surface
10
ascsnding or descending flows. The aerostatic force affects the angle and
distance of glide. During s^aneuyering, the aerostatic force increase• the
angular •peed and decreasas the turn radius, but dozing levaling off, besides
decreasing the radius of curvature, it also reduces the •peed along the tra-
jectory.
The speed of horizontal flight regains constant independent of the altitude
of ascent or depth of descent, if the area of the body changes in correspond-
-	 enca with the changes of the density of the medium and the aerostatic ford
regains constant during this change.
The speed, range of flight, and lift capability of a Venus flight vehicle at
low alt itude amount to 18.5, 40, and 14 percent, respectively, of the analo-
gous parameters of terrestrial flight vehicles. In this fashion, the pres-
ence of the aerostatic force opeus up new possibilities for the perfection
and formation of varied forms of movement, even new and yet unknown ones,
which is especially important for Venus flight vehicles.
Density and barometric pressure decrease during ascent. For this reason, the
mass of the gas envelope has to be increased and the mass of the hermetically
sealed gondola decreased. Loring descent, on the other hand, th^s mass of the
envelope has to decrease and the mass of the gondola increase. fihese factors,
which act opposite to each other, determine the optimum altitudt fir cruising
flight, at which the mss• of the Venus vehicle becomes a minimum. Presence
of as oaboard cooling aystsm with a increased life will make possible flights 	 -
in the region of decreased temperatures. Thus, for drift times not exceeding
10 hours. the optimum altitude of flight is approximately 40 km ( temperature
at this altitude is 140'C).
In view of the high temperatures on Venus, the most likely vehicle designs
are those that will use ammonia and its solutions as a working fluid (for
producing the aerostatic force). Such tropospheric vehicles must have a
larger lift capability than systems that use a light gas (hydrogen or helium),
with their attendant heavy and bulky high-pressure balloons.
In spite of apparent contradictions, there exists a certain analogy between
aerostatic flight vehicles and spacecraft. In motion, the character (but not
the gagnitude) of speed, loading, and distance tzaveled remains similar. We
can compare vehicles that enter the dense layers of the atmosphere at high
velocities to aerostatic vehicles than fly in the descent regime with absence
of active forces; vehicles that enter the dense layers of the atmosphere at
low velocities and aerostatic vehicles flying in the descent regime undez
action of active forces; the rocket lifting off vertically through a resist-
ing medium and the aerostatic flight v^ :hicle flying in the ascent regime under
the action of forces aligned with the vector of velocity.
Analysis of flight vehicles sho a that, in spite of the comglex aerothermody-
namic conditions, flight in the atmosphere of Venus is possible. This result
is important for the reason that it opens up the opportunity to study the
planet with the aid of special flight equipment.
COPYRIGHT: Tzdatel'stvo "'vr.uka", "Zemlya i t^selennaya", 1979
11


Spacecraft for flight in the atmosphere of Venus

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