Development and characteristics of hot air balloon deceleration and recovery syste

Dunavant, J. C.

Scher, S. H.

English

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A~~~~ 70 S. H. SCWER E T A L  
HOT AIR BALLOON DECELERATION AND RECOVERY SYSTEM 
Original  Filed Aug. 31, 1967 
12 
* 
STANLEY H. SCHER 
BY JAMES C. DUNAVANT 
A 7+T 0 RNE Y S 
1 72 
atented Apr. 28, 1970 
3,5Q8,724 
~ ~ Q V E ~ Y  SYSTEM 
Stanley H. dcher, Newport News, and James C. Duna- 
vant, Uorktown, va., assignors to the United States af 
Ameiica as represented by the Administrator of the 
National Aeronautics and Space Administration 
Continuatiob of abandoned application der. No. 665,682, 
Aug. 31, 1967. This application NQV. 14, 1968, Ser. 
No. 775,966 
U.S. CI. 244-31 10 Claims 
ABSTRACT OF DISCLOSURE 
A deceleration and recovery system employing a hot 
air balloon with ram-type openings through which aero- 
dynamically heated atmosphere enters and inflates the 
balloon during deceleration, thus causing the balloon to 
become buoyant. 
B A ~ ~ Q Q ~  ~ E E ~ E ~ A ~ O N  AND 
Int. C1. B64b 1/40, 3/62; 
This application is a continuation of Ser. No. 665,682, 
filed Aug. 3 1, 1967, now abandoned. 
The invention described herein was made by employees 
of the United States Government and may be manufac- 
tured and used by or for the Government for govern- 
mental purposes without the payment of any royalties 
thereon or therefor. 
This invention relates generally to the field of de- 
celeration and recovery of high speed bodies and more 
particularly to a system for making such recoveries em- 
ploying a hot air ballon. 
A dificult problem obstructing advancement of space 
exploration is that of decelerating and recovering equip- 
ment shot into space such as rocket boosters and satel- 
lites. Most prior art recovery systems have used para- 
chutes to decelerate space equipment and to lower it to 
impact at a relatively slow speed; however, it has still 
been necessary to cushion the impact by having it fall 
into the ocean. One disadvantage of such a system has 
been that the space equipment must be water-resistant and 
able to float, and this disadvantage alone has made re- 
covery of booster rockets virtually impossible. Balloon 
systems have also been suggested for making recoveries. 
Although it is believed that a balloon could be used 
both as a drag and as a buoyant device for decelerating 
and recovering, balloon systems have not been used be- 
cause of the large quantity of gas, and its attendant weight, 
that is required to inflate them. Hot air balloons have 
proven equally as impractical because of the large weight 
of fuel needed to heat the air. 
The significance of this invention was first revealed 
during a research program with a hot air balloon reentry 
syk'tem. It was though that by ming the aerodynamicall'y 
heated atmosphere, which occnrs naTwally during high- 
speed enti'y 5nVo  at^ atmosphere, to inflate the balloon, a 
weight savings on heater fuel could be made. Surpris- 
%kgIy, expedments disdosed that tae sys$em decelerated 
to zero yebciiy ' f o r e  impact without using the heater 
at all, The instant invention embodies this principle of 
inflating a hot air balloon with aerodfnamically heated 
atmosphere to effect the deceleration and recovery of a 
high-speed body. 
5 
10 
15 
20 
25 
30 
35 
40 
45 
50 
55 
60 
One object of this invention is to provide an improved 
lightweight system for decelerating and recovering all 
high-speed bodies. 
A further object of this invention is to provide a prac- 
tical system for rocket booster recovery and reentry from 
space using a hot air balloon. 
Still another object of this invention is to provide a 
hot air balloon recovery system which utilizes the high 
kinetic energy of the body (being recovered to M a t e  the 
balloon with hot atmosphere. 
Yet another object of the instant invention is to pro- 
vide a system for inflating a hot air balloon with aero- 
dynamically heated atmosphere and maintaining this air 
hot within the balloon. 
Another object of the invention is to provide a de- 
celeration and recovery system which floats the body 
being recovered in the atmosphere so that it might <be 
towed or propelled to the desired landing point. 
Further and additional objects of the invention will be- 
come obvious from a consideration of this specification, 
the accompanying drawings and the appended claims. 
For a more complete understanding of this invention 
reference will now be made to the accompanying draw- 
ings wherein: 
FIG. 1 is a side elevation view of a rocket booster in 
flight immediately after separation from the upper stage. 
FIG. 2 is a side elevation view of the booster still travel- 
ing up from momentum. 
FIG. 3 is a side elevation view of the booster at high 
altitude with a cutaway view of the attached balloon. 
FIG. 4 is a cutaway side elevation view of the booster 
and attached balloon falling at a high speed through the 
atmosphere with the associated shock wave being dia- 
gralflmatically represented. 
FIG. 5 is a cutaway side elevation view of &e booster 
being suspended in the atmosphere by the balloon which 
has reached the point of buoyancy. 
Referring now to the drawings wherein like reference 
numerals designate identical or corresponding parts 
throughout the several v'lews, and more particularly to 
FIG. 1, a two-stage space probe is shown in the ascent 
immediately after the rocket booster 10 has separated 
from the second stage 12. A folded balloon 13 is in a 
compartment attached at some convenient position on 
the booster 10. Also shown in FIGS. 1 and 2, is a small 
mass of gas 15 inside the balloon which is used to ini- 
tially inflate the balloon, such as a subliming material. 
Turning to FIG. 3, the numeral 14 designates an in- 
flated balloon of any suitable shape attached directly 
to the rocket booster 10; however, it could also be a€- 
tached thereto by lines. There are several materials avail- 
able for fabricating the balloon skin, the most likely 
being metal fabrics or glass fiber cloth. Atlhough either 
of these materials could understand the required heat 
and stress, it is anticipated that glass fiber cloth will 
prove to be more practical because it is cheaper. In FIG. 
a, it can be seen that the balloon has a plurality of open- 
iags 16 on which valves 20 are installed so that tit- 
mosphere flow into and out of the 'balloon can be rem- 
Iated. Although only two openings are shown, it is to 
be understood that they are spaced at intervals about the 
circumference of the balloon. Valves [of conventional 
design, which allow flow into the balloon but will not al- 
3,508,724 
3 
low flow out of the balloon, unless the internal pressure 
exceeds external pressure by a predetermined limit, are 
adequate to carry out the functions essentially to this in- 
vention, bdt more sophisticated valves may be used to give 
additional vertical control as is hereinafter explained. 
Scoops 24 are attached to the balloon to channel atrnos- 
phere into the openings 16 but the size and shape of such 
scoops, must be carefully optimized as is hereinafter ex- 
plained. The openings 16 with associated scoops 24 must 
be located so that as the system falls through the atmos- 
phere, atmosphere is forced through the openings by a ram 
action. Numeral 18 designates a heater which is used to 
provide additional heat to the atmosphere in the balloon, 
and numeral 22 represents the shock wave which forms 
in front of the balloon-booster system as it falls through 
the atmsophere. 
Operation 
FIGS. 1-5, when viewed in sequence, show this in- 
vention as it is applied to decelerate and recover a rocket 
booster 10. It is to be understood that the booster 10 
is illustrative only of what might be recovered and that 
the invention has application to decelerate and recover 
any high speed vehicle. In FIG. 1, a two-stage space 
probe is shown in the ascent immediately after the rocket 
booster 10 has separated from the second stage 12. From 
momentum the booster continues to rise after separa- 
tion, as shown in FIG. 2, until reaching thin atmosphere 
at  which point the balloon 14 is distended (see FIG. 3) ,  
so that the valves 20 become exposed using a small in- 
ternal mass of gas 15, such as a subliming material. The 
amount of gas required is very small because the at- 
mosphere is so thin at  that altitude. Upon reaching its 
apogee, the booster and attached balloon begin the de- 
scent at an accelerating pace, as shown in FIG. 4, with 
the balloon creating drag and the whole system giving 
rise to a shock wave 22 out front. When the outside 
pressure on valves 20 becomes greater than the internal 
pressure, they swing open leaving openings 16 through 
which atmosphere enters the balloon. The gas which 
was originally used to inflate the balloon does not pre- 
vent entry of the atmosphere through the openings be- 
cause its mass is so small. Increased pressure at the open- 
ings 16 can be attained by constructing scoops 24 so 
as to funnel the atmosphere into the openings; however, 
they must be carefully designed not to increase the in- 
ternal pressure of the balloon beyond its bursting point. 
As can be seen in FIG. 4, the atmosphere which enters 
the openings 16 must first pass through the shock wave 
22 and is thereby heated due to the aerodynamic heat- 
ing phenomena. This atmosphere is further heated by 
being compressed within the balloon 14. Because of the 
drag of the balloon 14 and the buoyancy of the hot at- 
mosphere within the balloon, the system eventually de- 
celerates to zero velocity at which point the booster 10 
is suspended in the atmosphere by the fully charged hot 
air balloon 14, as is shown in FIG. 5. Here, the valves 
20 are closed to prevent the escape of hot atmosphere 
from the openings 16; however, they must be designed 
to allow relief of internal pressures above a predeter- 
mined limit. Eventually the atmosphere in the balloon 
will cool and the system will again begin its descent until 
finally impacting. Although it is possible to design the 
system so that it becomes suspended in the atmosphere 
at  a very low altitude and, therefore, impacts at a low 
velocity, most likely it will be desirous to prolong the 
period for which the system is suspended so that it can 
be propelled to the proper landing area and then brought 
to impact at  a regulated rate. For this purpose, a heater 
18 is used to maintain the atmosphere in the balloon at 
a high temperature; however, the size of the heater 18 
and the amount of fuel that it uses can be comparatively 
small because it does not have to bring the atmosphere 
up to the high temperature. After the booster is suspend- 
ed in the atmosphere it is retrieved by some flying de- 
4 
vice such as a helicopter or it could have a built-in pro- 
pulsion system such as that on a dirigible. For control- 
ling the rate of descent, the heater 18 and/or the valves 
20 can be used singly or in comlbination, with open 
valves accelerating descent and increased heat decelerat- 
ing descent. Additional valves could also be installed 
at the top of the balloon to provide added vertical control. 
In the above embodiment the balloon is distended by 
a small mass of gas so that the openings 16 and SCOOPS 
,() 24 become exposed to the airstream. If the openings and 
scoops were located close to the booster 10 they could 
be held exposed to the airstream by arms extending from 
the booster 10, and then no small mass of gas would be 
needed. 
There are many possible uses for this invention other 
than the recovery of booster rockets and reentry space- 
craft. A space probe entering the atmosphere of a planet 
could be decelerated and suspended in the atmosphere of 
the planet for the purpose of photographing the area 
20 over which it drifts. It is also possible that this system 
could be used to recover X15-type aircraft. 
mosphere a high velocity body comprising the step of: 
15 
What is claimed is: 
1. A method of decelerating and suspending in an at- 
inflating a balloon with hot air generated solely by an 
attached body having a speed sufficient to heat the 
surrounding atmosphere by the aerodynamic heating 
phenomena caused by the relative motion between 
the atmosphere and said body to a temperature suffi- 
cient to render the body floating, whereby said body 
is decelerated and suspended in the atmosphere. 
2. A method of decelerating and suspending in an at- 
mosphere a high velocity body as in claim 1, including 
the step of maintaining the atmosphere in the balloon hot 
3. A method of decelerating and suspending in an 
atmosphere a high velocity body as in claim 2 including 
the steps of cooling the atmosphere in the balloon; and 
regulating the amount of atmosphere in the balloon to al- 
4. A system for decelerating and suspending in an at- 
mosphere a high velocity body comprising : 
body means having an initial supersonic velocity; 
a balloon attached to said body and exposed to said 
means for inflating said balloon with the surrounding 
atmosphere which has been heated solely by the 
aerodynamic heating phenomena caused by the rela- 
tive motion between the atmosphere and said body 
said body means heating the surrounding atmosphere 
to a temperature such that its inflation of the bal- 
loon and compression in the balloon will cause the 
body to float whereby the body is decelerated and 
5. A system for decelerating and suspending in an at- 
mosphere a high velocity body as embodied in claim 4, 
wherein the means for inflating the balloon with aerody- 
namically heated atmosphere consists of: 
openings in the balloon; and 
scoop means fixed to said balloon adjacent said open- 
ings directing said heated atmosphere into the in- 
terior of the balloon. 
6. A system for decelerating and suspending in an at- 
G6 mosphere a high velocity body as embodied in claim § 
wherein the openings have attached thereto valves for 
regulating the flow of atmosphere to and from the bal- 
loon. 
7. A system for decelerating and suspending in an at- '' mosphere a high velocity body as embodied in claim § 
wherein means for exposing said openings to the air- 
stream prior to beginning deceleration are included. 
8. A system for decelerating and suspending in an at- 
75 mosphere a high velocity body as embodied in claim 7 
25 
30 
35 for sustained buoyancy. 
40 low landing said body on a hard surface. 
45 supersonic velocity; and 
50 means; 
55 suspended in the atmosphere. 
60 
3,508,724 
wherein the means for exposing said openings to the air- 
UNITED STATES PATENTS stream consists of a small internal mass of gas which distends the balloon, 
9. A system for decelerating and suspending in an at- 391319889 5/1964 yost- 
mosphere a high velocity body as embodied in claim 4 3~1689266 211965 yost. 
wherein auxiliary means for maintaining the atmosphere ' 392299932 1/1966 yost. 
within the balloon in its heated state after s a t i o n  has 3,350,040 1011967 Sims et al. -------- 244-113 X 
,been completed are included. 
10. A system for decelerating and suspending in an at- 
mosphere a high velocity body as embodied in claim 4 10 J. L. FORMAN, Assistant Examiner 
including means for regulating the heat resulting from 
compression of the heated atmosphere utilized in inflat- 
ing the balloon. 
BUCHLER7 Primary Examiner 
U.S. C1. X.R. 
244-1, 138, 113 


Hot air ballon deceleration and recovery system Patent

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