U.S. patent application number 15/048395 was filed with the patent office on 2016-06-16 for superpressure polyethylene balloon with load tapes.
The applicant listed for this patent is Google Inc.. Invention is credited to Kevin Roach.
Application Number | 20160167761 15/048395 |
Document ID | / |
Family ID | 55537357 |
Filed Date | 2016-06-16 |
United States Patent
Application |
20160167761 |
Kind Code |
A1 |
Roach; Kevin |
June 16, 2016 |
Superpressure Polyethylene Balloon With Load Tapes
Abstract
A balloon having a balloon envelope formed with a plurality of
adjacent envelope sections each formed of a single seamless piece
sealed together at their respective edges to form an edge seam
between each of the adjacent envelope sections, a tape comprised of
fibers applied to a centerline of each of the envelope sections,
wherein the envelope sections are constructed such that the edge
seam between each of the adjacent envelope sections is longer than
the centerline of each of the envelope sections, and wherein a load
caused by pressurized lifting gas within the balloon envelope is
carried primarily by the fiber tapes on the centerlines of the
envelope sections, rather than the edge seams between the adjacent
envelope sections.
Inventors: |
Roach; Kevin; (San Jose,
CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Google Inc. |
Mountain View |
CA |
US |
|
|
Family ID: |
55537357 |
Appl. No.: |
15/048395 |
Filed: |
February 19, 2016 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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14036933 |
Sep 25, 2013 |
9296461 |
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15048395 |
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Current U.S.
Class: |
244/31 ;
156/60 |
Current CPC
Class: |
B64B 1/40 20130101; B64B
1/58 20130101 |
International
Class: |
B64B 1/58 20060101
B64B001/58; B64B 1/40 20060101 B64B001/40 |
Claims
1. An apparatus comprising: a balloon envelope formed with a
plurality of adjacent envelope sections, each envelope section
comprising a single seamless piece, each adjacent envelope section
sealed together at their respective edges to form an edge seam
between each of the adjacent envelope sections; a tape comprised of
fibers applied to a seamless centerline of each of the envelope
sections; wherein the envelope sections are constructed such that
the edge seam between each of the adjacent envelope sections is
longer than the centerline of each of the envelope sections; and
wherein a load caused by pressurized lifting gas within the balloon
envelope is carried primarily by the fiber tapes on the centerlines
of the envelope sections, rather than the edge seams between the
adjacent envelope sections.
2. The apparatus of claim 1, wherein each of the respective
envelope sections and fiber tapes applied to the centerlines of the
envelope sections extend longitudinally to a load ring positioned
at a top of the balloon envelope.
3. The apparatus of claim 2, wherein each of the respective
envelope sections and fiber tapes are secured to the load ring and
sandwiched beneath a top plate positioned at the top of the balloon
envelope.
4. The apparatus of claim 2, wherein each of the respective fiber
tapes has a width of 1/2 inch.
5. The apparatus of claim 2, wherein a pressure sensitive adhesive
is applied to the respective fiber tapes before the fiber tapes are
applied to the seamless centerlines of the respective envelope
sections.
6. The apparatus of claim 2, wherein the fibers in the respective
fiber tapes are straight line fibers.
7. The apparatus of claim 6, wherein the straight line fibers are
comprised of dyneema fibers or aramid fibers.
8. The apparatus of claim 2, wherein the one or more of the
respective fiber tapes includes one or more metallic, reflective
fibers.
9. The apparatus of claim 8, wherein the one or more reflective
fibers serve as an antenna.
10. The apparatus of claim 1, wherein the respective fiber tapes
are positioned within a tubular sleeve that is adhered to the
respective seamless centerlines of the envelope sections.
11. A method of forming a balloon envelope comprising the steps of:
positioning a first envelope section formed as a seamless single
piece having a first edge and a second edge adjacent a second
envelope section formed as a single seamless piece having a first
edge and a second edge; sealing the second edge of the first
envelope section to the first edge of the second envelope section
to form a first edge seam; adhering a first fiber tape to a
seamless centerline of the first envelope section, wherein the
first edge seam has a length that is longer than a length of the
centerline of the first envelope section; positioning a third
envelope section formed as a seamless single piece having a first
edge and a second edge adjacent the second envelope section;
sealing the second edge of the second envelope section to the first
edge of the third envelope section to form a second edge seam;
adhering a second fiber tape to a seamless centerline of the second
envelope section, wherein the second edge seam has a length that is
longer than a length of the centerline of the second envelope
section; positioning a final envelope section formed as a seamless
single piece having a first edge and a second edge adjacent the
first envelope section; sealing the second edge of the final
envelope section to the first edge of the first envelope section to
form a final edge seam; adhering a third fiber tape to a seamless
centerline of the third envelope section, wherein the second edge
seam has a length that is longer than a length of the centerline of
the third envelope section; and adhering a final fiber tape to a
seamless centerline of the final envelope section, wherein the
final edge seam has a length that is longer than a centerline of
the final envelope section.
12. The method of claim 11, further including the step of securing
the respective envelope sections to a load ring at an apex of the
balloon envelope.
13. The method of claim 11, wherein the steps set forth in claim 11
are performed in the exact order listed.
14. The method of claim 11, wherein the respective envelope
sections are comprised of polyethylene.
15. The method of claim 11, wherein the respective fiber tapes have
a width of 1/2 inch.
16. The method of claim 11, wherein the fibers in the respective
fiber tapes are straight line fibers.
17. The method of claim 16, wherein the straight line fibers are
comprised of dyneema fibers or aramid fibers.
18. The method of claim 17, wherein the one or more of the
respective fiber tapes includes one or more metallic, reflective
fibers.
19. The method of claim 11, wherein a load caused by pressurized
lifting gas within the balloon envelope is carried primarily by the
fiber tapes on the centerlines of the envelope sections, rather
than the edge seams between the adjacent envelope sections.
20. The method of claim 19, wherein the respective fiber tapes are
positioned within a tubular sleeve that is adhered to the
respective seamless centerlines of the envelope sections.
21. An apparatus comprising: a balloon envelope formed with a
plurality of adjacent envelope sections each formed as a seamless
single piece sealed together at their respective edges to form an
edge seam between each of the adjacent envelope sections; a tubular
sleeve adhered to a seamless centerline of each of the envelope
sections; a tendon positioned within each of the respective tubular
sleeves; wherein the envelope sections are constructed such that
the edge seam between each of the adjacent envelope sections is
longer than the centerline of each of the envelope sections; and
wherein a load caused by pressurized lifting gas within the balloon
envelope is carried primarily by the tendons on the seamless
centerlines of the envelope sections, rather than the edge seams
between the adjacent envelope sections.
22. The apparatus of claim 21, wherein at least some of the tendons
are comprised of a fiber tape.
23. The apparatus of claim 21, wherein at least some of the tendons
are comprised of a straight fiber cable.
24. The apparatus of claim 1, wherein the envelope sections have a
coefficient of thermal expansion that matches a coefficient of
thermal expansion of the tape.
Description
BACKGROUND
[0001] Unless otherwise indicated herein, the materials described
in this section are not prior art to the claims in this application
and are not admitted to be prior art by inclusion in this
section.
[0002] Computing devices such as personal computers, laptop
computers, tablet computers, cellular phones, and countless types
of Internet-capable devices are increasingly prevalent in numerous
aspects of modern life. As such, the demand for data connectivity
via the Internet, cellular data networks, and other such networks,
is growing. However, there are many areas of the world where data
connectivity is still unavailable, or if available, is unreliable
and/or costly. Accordingly, additional network infrastructure is
desirable.
SUMMARY
[0003] In one aspect, a balloon is provided that is formed with a
plurality of envelope gores that are seamed together, where the
centerlines of the respective envelope gores are shorter than the
edge seams between adjacent envelope gores. A tendon is positioned
on the centerline of each of the respective envelope gores, and the
tops of the envelope gores are secured to a load ring positioned at
the top of the balloon envelope. A load caused by pressurized
lifting gas within the balloon envelope is carried primarily by the
tendons positioned on the centerlines of the envelope gores, rather
than the edge seams between the adjacent envelope gores. The tendon
may be formed as a fiber load tape that is adhered to the
centerline of the respective envelope gores. Alternately, a tubular
sleeve may be adhered to the centerlines of the respective
envelopes with the tendon positioned within the tubular sleeve. The
tendon could take the form of a fiber tape positioned within the
sleeve or a straight fiber cable positioned within the sleeve.
[0004] In one aspect, a balloon is provided having a balloon
envelope formed with a plurality of adjacent envelope gores sealed
together at their respective edges to form an edge seam between
each of the adjacent envelope gores, a tape comprised of fibers
applied to a centerline of each of the envelope gores, wherein the
envelope gores are constructed such that the edge seam between each
of the adjacent envelope gores is longer than the centerline of
each of the envelope gores, and wherein a load caused by
pressurized lifting gas within the balloon envelope is carried
primarily by the fiber tapes on the centerlines of the envelope
gores, rather than the edge seams between the adjacent envelope
gores.
[0005] In another aspect, a method of forming a balloon envelope is
provided including the steps of positioning a first envelope gore
having a first edge and a second edge adjacent a second envelope
gore having a first edge and a second edge, sealing the second edge
of the first envelope gore to the first edge of the second envelope
gore to form a first edge seam, adhering a first fiber tape to a
centerline of the first envelope gore, wherein the first edge seam
has a length that is longer than a length of the centerline of the
first envelope gore, positioning a third envelope gore having a
first edge and a second edge adjacent the second envelope gore,
sealing the second edge of the second envelope gore to the first
edge of the third envelope gore to form a second edge seam,
adhering a second fiber tape to a centerline of the second envelope
gore, wherein the second edge seam has a length that is longer than
a length of the centerline of the second envelope gore, positioning
a final envelope gore having a first edge and a second edge
adjacent the first envelope gore, sealing the second edge of the
final envelope gore to first edge of the first envelope gore to
form a final edge seam, and adhering a final fiber tape to a
centerline of the final envelope gore, wherein the final edge seam
has a length that is longer than a centerline of the final
envelope.
[0006] In another aspect, a balloon is provided having a balloon
envelope formed with a plurality of adjacent envelope gores sealed
together at their respective edges to form an edge seam between
each of the adjacent envelope gores, a tubular sleeve adhered to a
centerline of each of the envelope gores, a tendon positioned
within each of the respective tubular sleeves, wherein the envelope
gores are constructed such that the edge seam between each of the
adjacent envelope gores is longer than the centerline of each of
the envelope gores, and wherein a load caused by pressurized
lifting gas within the balloon envelope is carried primarily by the
tendons on the centerlines of the envelope gores, rather than the
edge seams between the adjacent envelope gores.
[0007] In a further aspect, a balloon envelope is provided having
means for primarily carrying a load caused by pressurized lifting
gas within the balloon envelope on the centerlines of the envelope
gores, rather than the edge seams between the adjacent envelope
gores.
[0008] These as well as other aspects, advantages, and
alternatives, will become apparent to those of ordinary skill in
the art by reading the following detailed description, with
reference where appropriate to the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] FIG. 1 is a simplified block diagram illustrating a balloon
network, according to an example embodiment.
[0010] FIG. 2 is a simplified block diagram illustrating a
high-altitude balloon, according to an example embodiment.
[0011] FIG. 3 shows a perspective view of a balloon envelope 10
comprised of a plurality of envelope gores having fiber load tapes
extending down the centerline of the respective gores, according to
an example embodiment.
[0012] FIG. 4A shows a side view of the respective envelope gores
and fiber load tapes prior to forming balloon envelope 10 in FIG.
3, according to an example embodiment.
[0013] FIG. 4B shows a side view of the respective envelope gores
and fiber load tapes shown in FIG. 4A after the adjacent envelope
gores have been seamed together and after the fiber load tapes have
been positioned on the centerlines of the respective envelope
gores.
[0014] FIG. 5A is a perspective view of a portion of the balloon
envelope 10 shown in FIG. 3.
[0015] FIG. 5B is a side view of one of the fiber load tapes shown
in FIGS. 3-5A, according to an example embodiment.
[0016] FIG. 6A is a perspective view of a portion of the top of
balloon envelope 10 shown in FIGS. 3 and 5A, according to an
example embodiment.
[0017] FIG. 6B is another perspective view of a portion of the top
of balloon envelope 10 shown in FIGS. 3 and 5A, according to an
example embodiment.
[0018] FIG. 7 is a cross-sectional view of a the connection of the
balloon envelope 10 to a load ring 70 and structural ring 60 shown
in FIGS. 6A and 6B, according to an example embodiment.
[0019] FIG. 8 is a perspective view of load ring 70 shown in FIGS.
6B and 7, according to an example embodiment.
[0020] FIG. 9 is a method, according to an example embodiment.
DETAILED DESCRIPTION
[0021] Example methods and systems are described herein. Any
example embodiment or feature described herein is not necessarily
to be construed as preferred or advantageous over other embodiments
or features. The example embodiments described herein are not meant
to be limiting. It will be readily understood that certain aspects
of the disclosed systems and methods can be arranged and combined
in a wide variety of different configurations, all of which are
contemplated herein.
[0022] Furthermore, the particular arrangements shown in the
Figures should not be viewed as limiting. It should be understood
that other embodiments may include more or less of each element
shown in a given Figure. Further, some of the illustrated elements
may be combined or omitted. Yet further, an example embodiment may
include elements that are not illustrated in the Figures.
1. Overview
[0023] Example embodiments help to provide a data network that
includes a plurality of balloons; for example, a mesh network
formed by high-altitude balloons deployed in the stratosphere.
Since winds in the stratosphere may affect the locations of the
balloons in a differential manner, each balloon in an example
network may be configured to change its horizontal position by
adjusting its vertical position (i.e., altitude). For instance, by
adjusting its altitude, a balloon may be able find winds that will
carry it horizontally (e.g., latitudinally and/or longitudinally)
to a desired horizontal location.
[0024] Further, in an example balloon network, the balloons may
communicate with one another using free-space optical
communications. For instance, the balloons may be configured for
optical communications using lasers and/or ultra-bright LEDs (which
are also referred to as "high-power" or "high-output" LEDs). In
addition, the balloons may communicate with ground-based station(s)
using radio-frequency (RF) communications.
[0025] Exemplary embodiments may be implemented in association with
a data network that includes a plurality of balloons. In an
exemplary embodiment, such balloons may include an envelope and a
payload. The balloon envelope is filled with a pressurized lifting
gas, such as helium or hydrogen, to provide buoyancy to the balloon
and to maintain the balloon envelope aloft. It will be appreciated
that the lifting gas must provide a sufficient lift force to raise
the balloon envelope to a desired altitude, and to maintain a
desired altitude. As a result, it is desirable to make the
components of the balloon system, including the balloon envelope,
as lightweight as possible, as the lighter the balloon system the
less lift force is required from the lifting gas. There is a
trade-off between envelope weight and envelope strength. Thus, a
thicker or stronger envelope material may provide for greater
strength but at a cost of an increase in overall weight of the
balloon system. To reduce the overall weight of the balloon system,
however, it is desirable to provide a lightweight balloon
envelope.
[0026] In view of these goals, the envelope may be comprised of a
thin film, such as polyethylene or polyethylene terephthalate,
which is lightweight yet has suitable strength properties for use
as a balloon envelope. Nonetheless, to provide additional strength
and stability to the balloon system, a series of spaced tendons
that run longitudinally from the top of the balloon envelope to the
bottom of the balloon envelope may be used. However, the tendons
around the outside of the envelope tend to slip relative to the
envelope unless they are held rigid relative to each other or to
the balloon envelope. One approach is to use tendons comprised of
braided fiber ropes which may be positioned within longitudinal
sealed edge seam sleeves on the exterior of the balloon
envelope.
[0027] However, as noted in more detail below, it may be desirable
to position the longitudinal tendons on the centerlines of the
respective envelope gores, rather than on the edge seams between
adjacent envelope gores, and thus without using edge seam sleeves
formed at the edge seams between adjacent envelope gores. This
design of positioning the tendons at the centerlines of the gores
allows for reduced stress and strain on the balloon envelope, as
the load is designed to be carried primarily by the tendons
positioned on the centerlines of the respective envelope gores,
rather than the edge seams of the adjacent envelope gores.
[0028] One approach to affixing the longitudinal tendons to the
centerlines of the envelope gores is to use tape tacks that are
adhered to the balloon envelope. However, the tape tacks are not
that strong and do not adhere well to the balloon envelope. As a
result, forces on the tape tacks cause slippage which can unseat
the tape tacks or tendons, leading to buckling and rolling of the
tendons, or even the pulling loose of the tape tacks that can cause
damage to the balloon envelope.
[0029] Furthermore, while the braided tendons that have been used
as longitudinal tendons tend to advantageously stretch under
loading, they tend to have less strength than straight fibers, as
straight fibers are less prone to creep rupture and are stronger
under uni-axial loading. Therefore, it would be desirable to come
up with a method of forming a balloon envelope without using tendon
edge seam sleeves or tape tacks, and that could utilize straight
fibers for increased strength.
[0030] Example embodiments may be directed to forming an envelope
using a series of envelope gores that are seamed together using a
heat sealing process. The individual envelope gores may be shaped
so that the length of the seam connecting adjacent envelope gores
is greater than the length of the centerline of the envelope gores.
Thus, the envelope gores may be shaped to better optimize the
strain rate experienced by the balloon envelope.
[0031] In addition, instead of using edge seam sleeves with
enclosed tendons, or even braided tendons, a wide tape comprised of
straight fibers may be used in place of tendons. Thus, straight
fibers, such as dyneema fibers or UV resistant aramid fibers may be
aligned into a wide tape. A pressure sensitive adhesive may be
placed on the back side of the wide tapes. Then, the wide tapes of
straight fibers may be applied to and adhered to the centerlines of
the respective envelope gores to serve as an alternative to the use
of longitudinal tendons, or longitudinal tendons housed in edge
seam sleeves.
[0032] An alternate solution to the tape tack problem is to adhere
a narrow, adhesive backed polyethylene tube or sleeve to the
centerline of the respective envelope gores. A longitudinal tendon
may then be placed within the tubular sleeve. The tendon may be a
straight fiber cable or it could be a fiber tape positioned within
the sleeve. The use of a tube allows for some horizontal slop in
tendon movement and also keeps the tendon free of the adhesive
portions.
[0033] Thus, two approaches may be used to position a tendon on the
centerlines of the respective envelope gores without utilizing edge
seams formed at the edge seams of the respective envelope gores and
without using tape tacks. In the first approach, a straight fiber
tape may be adhered directly to centerlines of the respective
envelope gores. In the second approach, a tubular sleeve is adhered
to the centerlines of the respective envelope gores. A longitudinal
tendon may then be placed within the tubular sleeve. The tendon may
be a straight fiber cable or it could be a fiber tape positioned
within the sleeve.
[0034] The heat sealing of the individual envelope gores to form
edge seams between adjacent envelope gores, and application of the
straight fiber tape to the centerlines of the envelope gores is
easier to automate than the prior approach of using tape tacks to
adhere the braided tendons to the balloon envelope. Thus, this
balloon envelope design, and the method of making this balloon
envelope design, could utilize a manufacturing process that is more
automated and able to be converted to machine production, allowing
for an increase in production volume and a reduction in costs. The
repetitive steps of heat sealing the adjacent envelope gores and
applying the fiber tapes (or tubular sleeves) to the centerlines of
the envelope gores can be more readily machine controlled for
tolerances.
[0035] Furthermore, the individual envelope gores may be shaped so
that the length of the seam connecting adjacent envelope gores is
greater than the length of the centerline of the envelope gores.
Therefore, when inflated, there is an excess of envelope material
(that includes the edge seam between adjacent envelope gores)
between the respective longitudinal fiber tapes that bulges out
somewhat before there is any strain on the envelope material, as
the load is instead applied to the shortest section of the envelope
gore--the centerline where the longitudinal fiber load tapes has
been applied (or where the tendon within the tubular sleeve is
positioned). Thus, the balloon envelope may take on more of a
"pumpkin" shape with the edge seams of the respective envelope
gores bulging outward between the respective longitudinal fiber
load tapes (or tendons within tubular sleeves). This design allows
for reduced stress and strain on the balloon envelope, as the load
is designed to be carried primarily by the longitudinal fiber load
tapes (or tendons within tubular sleeves), rather than the balloon
envelope material.
[0036] Using longitudinal fiber load tapes, instead of tendons
positioned with tape tacks, reduces the risk of tangling, sliding,
and uneven deployment during superpressure transition, as well as
during handling and shipping.
[0037] In some embodiments, it may be desirable to have the
coefficient of thermal expansion (CTE) of the fiber load tapes
closely match the CTE of the envelope material. In this manner, the
balloon systems can operate during the extreme environmental
temperature ranges experienced when the balloon envelope is
deployed at altitude.
[0038] In addition, different items may be attached to the fiber
load tapes or tubular sleeves without directly contacting the
balloon envelope. Furthermore, the fiber load tapes or tubular
sleeves may also include one or more metallic, reflective fibers
that could make the balloon system visible to aircraft or to serve
as an antenna.
2. Example Balloon Networks
[0039] In some embodiments, a high-altitude-balloon network may be
homogenous. That is, the balloons in a high-altitude-balloon
network could be substantially similar to each other in one or more
ways. More specifically, in a homogenous high-altitude-balloon
network, each balloon is configured to communicate with one or more
other balloons via free-space optical links. Further, some or all
of the balloons in such a network, may additionally be configured
to communicate with ground-based and/or satellite-based station(s)
using RF and/or optical communications. Thus, in some embodiments,
the balloons may be homogenous in so far as each balloon is
configured for free-space optical communication with other
balloons, but heterogeneous with regard to RF communications with
ground-based stations.
[0040] In other embodiments, a high-altitude-balloon network may be
heterogeneous, and thus may include two or more different types of
balloons. For example, some balloons in a heterogeneous network may
be configured as super-nodes, while other balloons may be
configured as sub-nodes. It is also possible that some balloons in
a heterogeneous network may be configured to function as both a
super-node and a sub-node. Such balloons may function as either a
super-node or a sub-node at a particular time, or, alternatively,
act as both simultaneously depending on the context. For instance,
an example balloon could aggregate search requests of a first type
to transmit to a ground-based station. The example balloon could
also send search requests of a second type to another balloon,
which could act as a super-node in that context. Further, some
balloons, which may be super-nodes in an example embodiment, can be
configured to communicate via optical links with ground-based
stations and/or satellites.
[0041] In an example configuration, the super-node balloons may be
configured to communicate with nearby super-node balloons via
free-space optical links. However, the sub-node balloons may not be
configured for free-space optical communication, and may instead be
configured for some other type of communication, such as RF
communications. In that case, a super-node may be further
configured to communicate with sub-nodes using RF communications.
Thus, the sub-nodes may relay communications between the
super-nodes and one or more ground-based stations using RF
communications. In this way, the super-nodes may collectively
function as backhaul for the balloon network, while the sub-nodes
function to relay communications from the super-nodes to
ground-based stations.
[0042] FIG. 1 is a simplified block diagram illustrating a balloon
network 100, according to an example embodiment. As shown, balloon
network 100 includes balloons 102A to 102F, which are configured to
communicate with one another via free-space optical links 104.
Balloons 102A to 102F could additionally or alternatively be
configured to communicate with one another via RF links 114.
Balloons 102A to 102F may collectively function as a mesh network
for packet-data communications. Further, at least some of balloons
102A and 102B may be configured for RF communications with
ground-based stations 106 and 112 via respective RF links 108.
Further, some balloons, such as balloon 102F, could be configured
to communicate via optical link 110 with ground-based station
112.
[0043] In an example embodiment, balloons 102A to 102F are
high-altitude balloons, which are deployed in the stratosphere. At
moderate latitudes, the stratosphere includes altitudes between
approximately 10 kilometers (km) and 50 km altitude above the
surface. At the poles, the stratosphere starts at an altitude of
approximately 8 km. In an example embodiment, high-altitude
balloons may be generally configured to operate in an altitude
range within the stratosphere that has relatively low wind speed
(e.g., between 5 and 20 miles per hour (mph)).
[0044] More specifically, in a high-altitude-balloon network,
balloons 102A to 102F may generally be configured to operate at
altitudes between 18 km and 25 km (although other altitudes are
possible). This altitude range may be advantageous for several
reasons. In particular, this layer of the stratosphere generally
has relatively low wind speeds (e.g., winds between 5 and 20 mph)
and relatively little turbulence. Further, while the winds between
18 km and 25 km may vary with latitude and by season, the
variations can be modeled in a reasonably accurate manner.
Additionally, altitudes above 18 km are typically above the maximum
flight level designated for commercial air traffic. Therefore,
interference with commercial flights is not a concern when balloons
are deployed between 18 km and 25 km.
[0045] To transmit data to another balloon, a given balloon 102A to
102F may be configured to transmit an optical signal via an optical
link 104. In an example embodiment, a given balloon 102A to 102F
may use one or more high-power light-emitting diodes (LEDs) to
transmit an optical signal. Alternatively, some or all of balloons
102A to 102F may include laser systems for free-space optical
communications over optical links 104. Other types of free-space
optical communication are possible. Further, in order to receive an
optical signal from another balloon via an optical link 104, a
given balloon 102A to 102F may include one or more optical
receivers. Additional details of example balloons are discussed in
greater detail below, with reference to FIG. 3.
[0046] In a further aspect, balloons 102A to 102F may utilize one
or more of various different RF air-interface protocols for
communication with ground-based stations 106 and 112 via respective
RF links 108. For instance, some or all of balloons 102A to 102F
may be configured to communicate with ground-based stations 106 and
112 using protocols described in IEEE 802.11 (including any of the
IEEE 802.11 revisions), various cellular protocols such as GSM,
CDMA, UMTS, EV-DO, WiMAX, and/or LTE, and/or one or more propriety
protocols developed for balloon-ground RF communication, among
other possibilities.
[0047] In a further aspect, there may be scenarios where RF links
108 do not provide a desired link capacity for balloon-to-ground
communications. For instance, increased capacity may be desirable
to provide backhaul links from a ground-based gateway, and in other
scenarios as well. Accordingly, an example network may also include
downlink balloons, which could provide a high-capacity air-ground
link.
[0048] For example, in balloon network 100, balloon 102F is
configured as a downlink balloon. Like other balloons in an example
network, a downlink balloon 102F may be operable for optical
communication with other balloons via optical links 104. However, a
downlink balloon 102F may also be configured for free-space optical
communication with a ground-based station 112 via an optical link
110. Optical link 110 may therefore serve as a high-capacity link
(as compared to an RF link 108) between the balloon network 100 and
the ground-based station 112.
[0049] Note that in some implementations, a downlink balloon 102F
may additionally be operable for RF communication with ground-based
stations 106. In other cases, a downlink balloon 102F may only use
an optical link for balloon-to-ground communications. Further,
while the arrangement shown in FIG. 1 includes just one downlink
balloon 102F, an example balloon network can also include multiple
downlink balloons. On the other hand, a balloon network can also be
implemented without any downlink balloons.
[0050] In other implementations, a downlink balloon may be equipped
with a specialized, high-bandwidth RF communication system for
balloon-to-ground communications, instead of, or in addition to, a
free-space optical communication system. The high-bandwidth RF
communication system may take the form of an ultra-wideband system,
which may provide an RF link with substantially the same capacity
as one of the optical links 104. Other forms are also possible.
[0051] Ground-based stations, such as ground-based stations 106
and/or 112, may take various forms. Generally, a ground-based
station may include components such as transceivers, transmitters,
and/or receivers for communication via RF links and/or optical
links with a balloon network. Further, a ground-based station may
use various air-interface protocols in order to communicate with a
balloon 102A to 102F over an RF link 108. As such, ground-based
stations 106 and 112 may be configured as an access point via which
various devices can connect to balloon network 100. Ground-based
stations 106 and 112 may have other configurations and/or serve
other purposes without departing from the scope of the
invention.
[0052] In a further aspect, some or all of balloons 102A to 102F
could be configured to establish a communication link with
space-based satellites in addition to, or as an alternative to, a
ground-based communication link. In some embodiments, a balloon may
communicate with a satellite via an optical link. However, other
types of satellite communications are possible.
[0053] Further, some ground-based stations, such as ground-based
stations 106 and 112, may be configured as gateways between balloon
network 100 and one or more other networks. Such ground-based
stations 106 and 112 may thus serve as an interface between the
balloon network and the Internet, a cellular service provider's
network, and/or other types of networks. Variations on this
configuration and other configurations of ground-based stations 106
and 112 are also possible.
2a) Mesh Network Functionality
[0054] As noted, balloons 102A to 102F may collectively function as
a mesh network. More specifically, since balloons 102A to 102F may
communicate with one another using free-space optical links, the
balloons may collectively function as a free-space optical mesh
network.
[0055] In a mesh-network configuration, each balloon 102A to 102F
may function as a node of the mesh network, which is operable to
receive data directed to it and to route data to other balloons. As
such, data may be routed from a source balloon to a destination
balloon by determining an appropriate sequence of optical links
between the source balloon and the destination balloon. These
optical links may be collectively referred to as a "lightpath" for
the connection between the source and destination balloons.
Further, each of the optical links may be referred to as a "hop" on
the lightpath.
[0056] To operate as a mesh network, balloons 102A to 102F may
employ various routing techniques and self-healing algorithms. In
some embodiments, a balloon network 100 may employ adaptive or
dynamic routing, where a lightpath between a source and destination
balloon is determined and set-up when the connection is needed, and
released at a later time. Further, when adaptive routing is used,
the lightpath may be determined dynamically depending upon the
current state, past state, and/or predicted state of the balloon
network.
[0057] In addition, the network topology may change as the balloons
102A to 102F move relative to one another and/or relative to the
ground. Accordingly, an example balloon network 100 may apply a
mesh protocol to update the state of the network as the topology of
the network changes. For example, to address the mobility of the
balloons 102A to 102F, balloon network 100 may employ and/or adapt
various techniques that are employed in mobile ad hoc networks
(MANETs). Other examples are possible as well.
[0058] In some implementations, a balloon network 100 may be
configured as a transparent mesh network. More specifically, in a
transparent balloon network, the balloons may include components
for physical switching that is entirely optical, without any
electrical components involved in the physical routing of optical
signals. Thus, in a transparent configuration with optical
switching, signals travel through a multi-hop lightpath that is
entirely optical.
[0059] In other implementations, the balloon network 100 may
implement a free-space optical mesh network that is opaque. In an
opaque configuration, some or all balloons 102A to 102F may
implement optical-electrical-optical (OEO) switching. For example,
some or all balloons may include optical cross-connects (OXCs) for
OEO conversion of optical signals. Other opaque configurations are
also possible. Additionally, network configurations are possible
that include routing paths with both transparent and opaque
sections.
[0060] In a further aspect, balloons in an example balloon network
100 may implement wavelength division multiplexing (WDM), which may
help to increase link capacity. When WDM is implemented with
transparent switching, physical lightpaths through the balloon
network may be subject to the "wavelength continuity constraint."
More specifically, because the switching in a transparent network
is entirely optical, it may be necessary to assign the same
wavelength for all optical links on a given lightpath.
[0061] An opaque configuration, on the other hand, may avoid the
wavelength continuity constraint. In particular, balloons in an
opaque balloon network may include the 0E0 switching systems
operable for wavelength conversion. As a result, balloons can
convert the wavelength of an optical signal at each hop along a
lightpath. Alternatively, optical wavelength conversion could take
place at only selected hops along the lightpath.
[0062] Further, various routing algorithms may be employed in an
opaque configuration. For example, to determine a primary lightpath
and/or one or more diverse backup lightpaths for a given
connection, example balloons may apply or consider shortest-path
routing techniques such as Dijkstra's algorithm and k-shortest
path, and/or edge and node-diverse or disjoint routing such as
Suurballe's algorithm, among others. Additionally or alternatively,
techniques for maintaining a particular quality of service (QoS)
may be employed when determining a lightpath. Other techniques are
also possible.
2b) Station-Keeping Functionality
[0063] In an example embodiment, a balloon network 100 may
implement station-keeping functions to help provide a desired
network topology. For example, station-keeping may involve each
balloon 102A to 102F maintaining and/or moving into a certain
position relative to one or more other balloons in the network (and
possibly in a certain position relative to the ground). As part of
this process, each balloon 102A to 102F may implement
station-keeping functions to determine its desired positioning
within the desired topology, and if necessary, to determine how to
move to the desired position.
[0064] The desired topology may vary depending upon the particular
implementation. In some cases, balloons may implement
station-keeping to provide a substantially uniform topology. In
such cases, a given balloon 102A to 102F may implement
station-keeping functions to position itself at substantially the
same distance (or within a certain range of distances) from
adjacent balloons in the balloon network 100.
[0065] In other cases, a balloon network 100 may have a non-uniform
topology. For instance, example embodiments may involve topologies
where balloons are distributed more or less densely in certain
areas, for various reasons. As an example, to help meet the higher
bandwidth demands that are typical in urban areas, balloons may be
clustered more densely over urban areas. For similar reasons, the
distribution of balloons may be denser over land than over large
bodies of water. Many other examples of non-uniform topologies are
possible.
[0066] In a further aspect, the topology of an example balloon
network may be adaptable. In particular, station-keeping
functionality of example balloons may allow the balloons to adjust
their respective positioning in accordance with a change in the
desired topology of the network. For example, one or more balloons
could move to new positions to increase or decrease the density of
balloons in a given area. Other examples are possible.
[0067] In some embodiments, a balloon network 100 may employ an
energy function to determine if and/or how balloons should move to
provide a desired topology. In particular, the state of a given
balloon and the states of some or all nearby balloons may be input
to an energy function. The energy function may apply the current
states of the given balloon and the nearby balloons to a desired
network state (e.g., a state corresponding to the desired
topology). A vector indicating a desired movement of the given
balloon may then be determined by determining the gradient of the
energy function. The given balloon may then determine appropriate
actions to take in order to effectuate the desired movement. For
example, a balloon may determine an altitude adjustment or
adjustments such that winds will move the balloon in the desired
manner.
2c) Example Balloon Configuration
[0068] Various types of balloon systems may be incorporated in an
example balloon network. As noted above, an example embodiment may
utilize high-altitude balloons, which could typically operate in an
altitude range between 18 km and 25 km. FIG. 2 shows a
high-altitude balloon 200, according to an example embodiment. As
shown, the balloon 200 includes an envelope 202, a skirt 204, a
payload 206, and a cut-down system 208, which is attached between
the balloon 202 and payload 204.
[0069] The envelope 202 and skirt 204 may take various forms, which
may be currently well-known or yet to be developed. For instance,
the envelope 202 and/or skirt 204 may be made of materials
including metalized Mylar or BoPet. Additionally or alternatively,
some or all of the envelope 202 and/or skirt 204 may be constructed
from a highly-flexible latex material or a rubber material such as
chloroprene. Other materials are also possible. Further, the shape
and size of the envelope 202 and skirt 204 may vary depending upon
the particular implementation. Additionally, the envelope 202 may
be filled with various different types of gases, such as helium
and/or hydrogen. Other types of gases are possible as well.
[0070] The payload 206 of balloon 200 may include a processor 212
and on-board data storage, such as memory 214. The memory 214 may
take the form of or include a non-transitory computer-readable
medium. The non-transitory computer-readable medium may have
instructions stored thereon, which can be accessed and executed by
the processor 212 in order to carry out the balloon functions
described herein. Thus, processor 212, in conjunction with
instructions stored in memory 214, and/or other components, may
function as a controller of balloon 200.
[0071] The payload 206 of balloon 200 may also include various
other types of equipment and systems to provide a number of
different functions. For example, payload 206 may include an
optical communication system 216, which may transmit optical
signals via an ultra-bright LED system 220, and which may receive
optical signals via an optical-communication receiver 222 (e.g., a
photodiode receiver system). Further, payload 206 may include an RF
communication system 218, which may transmit and/or receive RF
communications via an antenna system 240.
[0072] The payload 206 may also include a power supply 226 to
supply power to the various components of balloon 200. The power
supply 226 could include a rechargeable battery. In other
embodiments, the power supply 226 may additionally or alternatively
represent other means known in the art for producing power. In
addition, the balloon 200 may include a solar power generation
system 227. The solar power generation system 227 may include solar
panels and could be used to generate power that charges and/or is
distributed by the power supply 226.
[0073] The payload 206 may additionally include a positioning
system 224. The positioning system 224 could include, for example,
a global positioning system (GPS), an inertial navigation system,
and/or a star-tracking system. The positioning system 224 may
additionally or alternatively include various motion sensors (e.g.,
accelerometers, magnetometers, gyroscopes, and/or compasses).
[0074] The positioning system 224 may additionally or alternatively
include one or more video and/or still cameras, and/or various
sensors for capturing environmental data.
[0075] Some or all of the components and systems within payload 206
may be implemented in a radiosonde or other probe, which may be
operable to measure, e.g., pressure, altitude, geographical
position (latitude and longitude), temperature, relative humidity,
and/or wind speed and/or wind direction, among other
information.
[0076] As noted, balloon 200 includes an ultra-bright LED system
220 for free-space optical communication with other balloons. As
such, optical communication system 216 may be configured to
transmit a free-space optical signal by modulating the ultra-bright
LED system 220. The optical communication system 216 may be
implemented with mechanical systems and/or with hardware, firmware,
and/or software. Generally, the manner in which an optical
communication system is implemented may vary, depending upon the
particular application. The optical communication system 216 and
other associated components are described in further detail
below.
[0077] In a further aspect, balloon 200 may be configured for
altitude control. For instance, balloon 200 may include a variable
buoyancy system, which is configured to change the altitude of the
balloon 200 by adjusting the volume and/or density of the gas in
the balloon 200. A variable buoyancy system may take various forms,
and may generally be any system that can change the volume and/or
density of gas in the envelope 202.
[0078] In an example embodiment, a variable buoyancy system may
include a bladder 210 that is located inside of envelope 202. The
bladder 210 could be an elastic chamber configured to hold liquid
and/or gas. Alternatively, the bladder 210 need not be inside the
envelope 202. For instance, the bladder 210 could be a rigid
bladder that could be pressurized well beyond neutral pressure. The
buoyancy of the balloon 200 may therefore be adjusted by changing
the density and/or volume of the gas in bladder 210. To change the
density in bladder 210, balloon 200 may be configured with systems
and/or mechanisms for heating and/or cooling the gas in bladder
210. Further, to change the volume, balloon 200 may include pumps
or other features for adding gas to and/or removing gas from
bladder 210. Additionally or alternatively, to change the volume of
bladder 210, balloon 200 may include release valves or other
features that are controllable to allow gas to escape from bladder
210. Multiple bladders 210 could be implemented within the scope of
this disclosure. For instance, multiple bladders could be used to
improve balloon stability.
[0079] In an example embodiment, the envelope 202 could be filled
with helium, hydrogen or other lighter-than-air material. The
envelope 202 could thus have an associated upward buoyancy force.
In such an embodiment, air in the bladder 210 could be considered a
ballast tank that may have an associated downward ballast force. In
another example embodiment, the amount of air in the bladder 210
could be changed by pumping air (e.g., with an air compressor) into
and out of the bladder 210. By adjusting the amount of air in the
bladder 210, the ballast force may be controlled. In some
embodiments, the ballast force may be used, in part, to counteract
the buoyancy force and/or to provide altitude stability.
[0080] In other embodiments, the envelope 202 could be
substantially rigid and include an enclosed volume. Air could be
evacuated from envelope 202 while the enclosed volume is
substantially maintained. In other words, at least a partial vacuum
could be created and maintained within the enclosed volume. Thus,
the envelope 202 and the enclosed volume could become
lighter-than-air and provide a buoyancy force. In yet other
embodiments, air or another material could be controllably
introduced into the partial vacuum of the enclosed volume in an
effort to adjust the overall buoyancy force and/or to provide
altitude control.
[0081] In another embodiment, a portion of the envelope 202 could
be a first color (e.g., black) and/or a first material from the
rest of envelope 202, which may have a second color (e.g., white)
and/or a second material. For instance, the first color and/or
first material could be configured to absorb a relatively larger
amount of solar energy than the second color and/or second
material. Thus, rotating the balloon such that the first material
is facing the sun may act to heat the envelope 202 as well as the
gas inside the envelope 202. In this way, the buoyancy force of the
envelope 202 may increase. By rotating the balloon such that the
second material is facing the sun, the temperature of gas inside
the envelope 202 may decrease. Accordingly, the buoyancy force may
decrease. In this manner, the buoyancy force of the balloon could
be adjusted by changing the temperature/volume of gas inside the
envelope 202 using solar energy. In such embodiments, it is
possible that a bladder 210 may not be a necessary element of
balloon 200. Thus, in various contemplated embodiments, altitude
control of balloon 200 could be achieved, at least in part, by
adjusting the rotation of the balloon with respect to the sun.
[0082] Further, a balloon 206 may include a navigation system (not
shown). The navigation system may implement station-keeping
functions to maintain position within and/or move to a position in
accordance with a desired topology. In particular, the navigation
system may use altitudinal wind data to determine altitudinal
adjustments that result in the wind carrying the balloon in a
desired direction and/or to a desired location. The
altitude-control system may then make adjustments to the density of
the balloon chamber in order to effectuate the determined
altitudinal adjustments and cause the balloon to move laterally to
the desired direction and/or to the desired location.
Alternatively, the altitudinal adjustments may be computed by a
ground-based or satellite-based control system and communicated to
the high-altitude balloon. In other embodiments, specific balloons
in a heterogeneous balloon network may be configured to compute
altitudinal adjustments for other balloons and transmit the
adjustment commands to those other balloons.
[0083] As shown, the balloon 200 also includes a cut-down system
208. The cut-down system 208 may be activated to separate the
payload 206 from the rest of balloon 200. The cut-down system 208
could include at least a connector, such as a balloon cord,
connecting the payload 206 to the envelope 202 and a means for
severing the connector (e.g., a shearing mechanism or an explosive
bolt). In an example embodiment, the balloon cord, which may be
nylon, is wrapped with a nichrome wire. A current could be passed
through the nichrome wire to heat it and melt the cord, cutting the
payload 206 away from the envelope 202.
[0084] The cut-down functionality may be utilized anytime the
payload needs to be accessed on the ground, such as when it is time
to remove balloon 200 from a balloon network, when maintenance is
due on systems within payload 206, and/or when power supply 226
needs to be recharged or replaced.
[0085] In an alternative arrangement, a balloon may not include a
cut-down system. In such an arrangement, the navigation system may
be operable to navigate the balloon to a landing location, in the
event the balloon needs to be removed from the network and/or
accessed on the ground. Further, it is possible that a balloon may
be self-sustaining, such that it does not need to be accessed on
the ground. In yet other embodiments, in-flight balloons may be
serviced by specific service balloons or another type of service
aerostat or service aircraft.
3. Example of a Balloon Envelope
[0086] As disclosed in FIGS. 3-8, the present embodiments provide a
balloon envelope 10 to which a payload 82 may be attached. The
balloon envelope 10 is filled with a pressurized lifting gas, such
as helium or hydrogen, to provide buoyancy to the balloon and to
maintain the balloon envelope 10 aloft. In view of the goal of
making the balloon envelope 10 as lightweight as possible, the
balloon envelope is comprised of a plurality of envelope gores
comprised of a thin film, such as polyethylene or polyethylene
terephthalate, which is lightweight yet has suitable strength
properties for use as a balloon envelope. FIGS. 3-8 show the
embodiment where the approach of adhering fiber load tapes directly
to the centerlines of the respective envelope gores is used.
However, it will be appreciated that the second approach of
adhering a tubular sleeve to the centerlines of the respective
gores having a tendon positioned within the tubular sleeves could
also be used in FIGS. 3-8.
[0087] FIG. 3 shows a perspective view of a balloon envelope 10
comprised of a plurality of envelope gores having fiber load tapes
extending down the centerline of the respective gores, according to
an example embodiment. In particular, balloon envelope 10 is
comprised of envelope gore 30 that is attached to adjacent envelope
31 at edge seam 30-31 and to adjacent envelope gore 29 at edge seam
29-30. Envelope gore 28 is shown attached to envelope gore 29 at
edge seam 28-29. Envelope gore 32 is shown attached to adjacent
envelope gore 31 at edge seam 31-32 and to adjacent envelope gore
33 at edge seam 32-33. Envelope gore 34 is shown attached to
envelope gore 33 at edge seam 33-34. The edge seams between
adjacent envelope gores may be formed by heat sealing, although
other means of attachment that provide for an air tight seal
between adjacent envelope gores may also be used. In a preferred
embodiment, the envelope gores are comprised of polyethylene having
a thickness of 1.5 to 2 mils. Each of the respective envelope gores
extend to balloon apex 20.
[0088] The individual envelope gores 28-34 may be shaped so that
the length of the edge seam connecting adjacent envelope gores is
greater than the length of a centerline of the envelope gores.
Thus, the envelope gores may be shaped to better optimize the
strain rate experienced by the balloon envelope. The pressurized
lifting gas within the balloon envelope causes a force or load to
be applied to the balloon envelope.
[0089] As noted above, in some embodiments longitudinal tendons may
be used to provide strength to the balloon envelope and to help
withstand the load created by the pressurized gas within the
balloon envelope. However, a wide tape comprised of straight fibers
may advantageously be used in place of tendons. Straight fibers,
such as dyneema fibers or UV resistant aramid fibers may be aligned
into a wide tape. A pressure sensitive adhesive may be placed on
the back side of the wide tapes. Then, the wide tape of straight
fibers may be applied to and adhered to the centerlines of the
respective gores. Example embodiments may include a 78000 denier
dyneema fiber tape with a 4500 pound load capacity or a jacketed
aramid straight fiber cable with a 3000 pound load capacity.
[0090] As shown in FIG. 3, fiber load tape 28' is shown positioned
on a centerline of envelope gore 28, fiber load tape 29' is shown
positioned on a centerline of envelope gore 29, fiber load tape 30'
is shown positioned on a centerline of envelope gore 30, fiber load
tape 31' is shown positioned on a centerline of envelope gore 31,
fiber load tape 32' is shown positioned on a centerline of envelope
gore 32, fiber load tape 33' is shown positioned on a centerline of
envelope gore 33, and fiber load tape 34' is shown positioned on a
centerline of envelope gore 34.
[0091] Furthermore, the individual gores 28-34 are shaped so that
the length of the edge seam connecting adjacent gores is greater
than the length of the centerline of the gores. Therefore, when
inflated, there is an excess of envelope material (that includes
the edge seams between the adjacent envelope gores) that bulges out
somewhat before there is any strain on the envelope material.
Therefore, the load is instead applied to the shortest section of
the gore--the centerline of the adjacent gores 28-34 where the
longitudinal fiber load tapes 28'-34' are applied. Thus, the
balloon envelope 10 takes on more of a "pumpkin" shape with the
edge seams 28-29, 29-30, 30-31, 31-32, 32-33, and 33-34 of the
respective envelope gores bulging outward between the respective
longitudinal fiber load tapes 28'-34'. This design allows for
reduced stress and strain on the balloon envelope 10, as the load
is designed to be carried primarily by the longitudinal fiber load
tapes 28'-34', rather than the balloon envelope material in
envelope gores 28-34.
[0092] Using longitudinal fiber load tapes, instead of tendons
positioned with tape tacks, reduces the risk of tangling, sliding,
and uneven deployment during superpressure transition, as well as
during handling and shipping.
[0093] FIG. 4A shows a side view of the respective envelope gores
28-32 and fiber load tapes 28'-32' prior to forming balloon
envelope 10 in FIG. 3, according to an example embodiment. In
particular, envelope gore 28 is shown prior to attachment to
adjacent envelope gore 29 and prior to the placement of fiber load
tape 28' onto envelope gore 28; envelope gore 29 is shown prior to
attachment to adjacent envelope gores 28 or 30 and prior to the
placement of fiber load tape 29' onto envelope gore 29, envelope
gore 30 is shown prior to attachment to adjacent envelopes gore 29
and 31 and prior to the placement of fiber load tape 30' onto
envelope gore 30, envelope gore 31 is shown prior to attachment to
adjacent envelope gores 30 and 32 and prior to the placement of
fiber load tape 31' onto envelope gore 31, and envelope gore 32 is
shown prior to attachment to adjacent envelope gore 31 and prior to
the placement of fiber load tape 32' onto envelope gore 32.
[0094] FIG. 4B shows a side view of the respective envelope gores
28-32 and fiber load tapes 28'-32' shown in FIG. 4A after the
adjacent gores 28-32 have been seamed together and after the fiber
load tapes 28'-32' have been positioned on the centerlines of the
respective gores 28-32. The adjacent gores may be attached to one
another by placing respective envelope gores on top of each other
and heat sealing the common edge on one side of the envelope gore
to form an edge seam. As shown in FIG. 4B, edge seam 28-29 is
formed between envelope gores 28 and 29, edge seam 29-30 is formed
between envelope gores 29 and 30, edge seam 30-31 is formed between
envelope gores 30 and 31, and edge seam 31-32 is formed between
envelope gores 31 and 32. Fiber load tapes 28'-32' are applied to
the centerlines of envelope gores 28-32 respectively. An adhesive
may be applied to the back of the fiber load tapes 28'-32' before
placement onto the respective envelope gores 28-32. The adhesive
may be a pressure sensitive adhesive.
[0095] The heat sealing of the individual envelope gores to form
seams between adjacent envelope gores, and application of the
straight fiber tape to the centerlines of the envelope gores is
easier to automate than the prior approach of using tape tacks to
adhere the braided tendons to the balloon envelope. Thus, this
balloon envelope design, and the method of making this balloon
envelope design, could utilize a manufacturing process that is more
automated and able to be converted to machine production, allowing
for an increase in production volume and a reduction in costs. The
repetitive steps of heat sealing the adjacent envelope gores and
applying the fiber load tapes to the centerlines of the gores can
be more readily machine controlled for tolerances.
[0096] FIG. 5A is a perspective view of a portion of the balloon
envelope 10 shown in FIG. 3. Envelope gore 29 is attached to
envelope gore 30 at edge seam 29-30. A fiber load tape 29' is shown
extending down a centerline of envelope gore 29 and a fiber load
tape 30' is shown extending down a centreline of envelope gore 30.
It should be noted that the envelope material of envelope gores 29
and 30 and edge seam 29-30 bulge outwardly between fiber load tapes
29' and 30'. In this manner, because the centerlines of gores 29
and 30 are shorter than the edge seam 29-30, the load caused by the
pressurized lifting gas within balloon envelope 10 is primarily
carried by fiber load tapes 29' and 30' rather than on the envelope
material and edge seam 29-30 between fiber load tapes 29' and
30'.
[0097] Similarly, envelope gore 30 is attached to envelope gore 31
at edge seam 30-31. A fiber load tape 31' is shown extending down a
centerline of envelope gore 31 and a fiber load tape 30' is shown
extending down a centerline of envelope gore 30. The envelope
material of envelope gores 30 and 31 and edge seam 30-31 bulge
outwardly between fiber load tapes 30' and 31'. Because the
centerlines of gores 30 and 31 are shorter than the edge seam
30-31, the load caused by the pressurized lifting gas within
balloon envelope 10 is primarily carried by fiber load tapes 30'
and 31' rather than on the envelope material and edge seam 29-30
between fiber load tapes 30' and 31'.
[0098] Furthermore, envelope gore 32 is shown attached to envelope
gore 31 at edge seam 31-32. Edge seams 29-30, 30-31, and 31-32
preferably are not covered by a load tape, as the design of balloon
envelope 10 is designed so that the load caused by the pressurized
gas within balloon envelope 10 is primarily carried by the fiber
load tapes 29', 30', and 31' rather than edge seams 29-30, 30-31,
or 31-32.
[0099] FIG. 5B is a side view of one of the fiber load tapes shown
in FIGS. 3-5A, according to an example embodiment. Fiber load tape
50 is comprised of a tape portion 52 and a plurality of fibers 54.
Fibers 54 are preferably straight fibers, such as such as dyneema
fibers or UV resistant aramid fibers, although other fibers could
also be used. Example embodiments could include a 7800 denier fiber
load that is 1/2 inch wide. Tape width is driven as much by the
size of the top fitting as it is by stability gained and adhesion
to the envelope. A narrower tape requires less real estate at the
apex and base of the envelope, reducing the size and weight of the
load rings, although a wider tape allows for better adhesion to the
envelope (if applied directly) and more lateral stability. However,
a tape that is too wide simply folds on itself which may be
problematic. A fiber load tape that is 1/2 inch wide provides a
suitable compromise.
[0100] In some embodiments, it may be desirable to have the
coefficient of thermal expansion (CTE) of the fiber tapes 50
closely match the CTE of the envelope material used in balloon
envelope 12. In this manner, the balloon systems can operate during
the extreme environmental temperature ranges experienced when the
balloon envelope is deployed at altitude. Matching CTE's allows the
tendons (whether load tape or straight fiber cable) to shorten in
the cold, carrying more of the load relative to the envelope
material. If the tendons do not shorten with the envelope material
in the stratosphere they need to be shortened prior to flight by an
equivalent amount. This shortening on the ground leads to the
possibility of uneven deployment of the tendons at float. Also, the
additional bunching of the envelope material during initial
pressurization that exists from shorter tendons is at risk of
pinching and damage.
[0101] In addition, with this design, different items may be
attached to the fiber load tapes without directly contacting the
balloon envelope. This provides an additional advantage of using
the fiber load tapes. Furthermore, the load tapes may also include
one or more metallic, reflective fiber that could make the balloon
system visible to aircraft or to serve as an antenna.
[0102] FIG. 6A is a perspective view of a portion of the top of
balloon envelope 10 shown in FIGS. 3 and 5A, according to an
example embodiment. A structural ring 60 is shown extending around
apex 20. Each of envelope gores 21-38 are shown extending from
structural ring 60. In particular envelope gore 21 is attached to
adjacent envelope gore 22 at edge seam 21-22; envelope gore 22 is
attached to adjacent envelope gore 23 at edge seam 22-23; envelope
gore 23 is attached to adjacent envelope gore 24 at edge seam
23-24; envelope gore 24 is attached to adjacent envelope gore 25 at
edge seam 24-25; envelope gore 25 is attached to adjacent envelope
gore 26 at edge seam 25-26; envelope gore 26 is attached to
adjacent envelope gore 27 at edge seam 26-27; envelope gore 27 is
attached to adjacent envelope gore 28 at edge seam 27-28; envelope
gore 28 is attached to adjacent envelope gore 29 at edge seam
28-29; and envelope gore 29 is attached to adjacent envelope gore
30 at edge seam 29-30.
[0103] Similarly, envelope gore 30 is attached to adjacent envelope
gore 31 at edge seam 30-31; envelope gore 31 is attached to
adjacent envelope gore 32 at edge seam 31-32; envelope gore 32 is
attached to adjacent envelope gore 33 at edge seam 32-33; envelope
gore 33 is attached to adjacent envelope gore 34 at edge seam
33-34; envelope gore 34 is attached to adjacent envelope gore 35 at
edge seam 34-35; envelope gore 35 is attached to adjacent envelope
gore 36 at edge seam 35-36; envelope gore 36 is attached to
adjacent envelope gore 37 at edge seam 36-37; envelope gore 37 is
attached to adjacent envelope gore 38 at edge seam 37-38, and
envelope gore 38 is attached to adjacent envelope gore 21 at final
edge seam 21-38. Fiber load tapes 21'-38' are adhered to the
centerlines of envelope gores 21-28 respectively.
[0104] FIG. 6B is another perspective view of a portion of the top
of balloon envelope 10 shown in FIGS. 3 and 5A, according to an
example embodiment. A load ring 70 is positioned adjacent
structural ring 60 and each of the envelope gores 21-28 and fiber
load tapes 21'-38' are secured to load ring 70. Bolts 62 are used
to secure the structural ring 70 and tops of the envelope gores
21-38 to the apex 20.
[0105] FIG. 7 is a cross-sectional view of a the connection of the
balloon envelope 10 to a load ring 70 and structural ring 60 shown
in FIGS. 6A and 6B, according to an example embodiment. In this
FIG. 7, a gasket 72 is positioned about load ring 70 between
envelope gore 30 and apex 20. Another gasket 74 is positioned
between apex 20 and structural ring 60, and bolt 62 is used to
squeeze apex 20, gaskets 72 and 74, and envelope gore 30 to form an
airtight seal.
[0106] FIG. 8 shows a perspective view of load ring 70 shown in
FIGS. 6B and 7, according to an example embodiment. Load ring 70
may comprise a number of angles 70a between straight members to
form load ring 70 into an overall circle.
4. Example Method of Forming a Balloon Envelope
[0107] FIG. 9 shows a method 1100 that may be used for forming a
balloon envelope 10 shown in FIGS. 3, 5A, 5B, and 6A. Method 1100
is provided that includes the step 1102 of positioning a first
envelope gore having a first edge and a second edge adjacent a
second envelope gore having a first edge and a second edge, the
step 1104 of sealing the second edge of the first envelope gore to
the first edge of the second envelope gore to form a first edge
seam, the step 1106 of adhering a first fiber tape to a centerline
of the first envelope gore, wherein the first edge seam has a
length that is longer than a length of the centerline of the first
envelope gore.
[0108] Method 1100 further includes the step 1108 of positioning a
third envelope gore having a first edge and a second edge adjacent
the second envelope gore, the step 1110 of sealing the second edge
of the second envelope gore to the first edge of the third envelope
gore to form a second edge seam, the step 1112 of adhering a second
fiber tape to a centerline of the second envelope gore, wherein the
second edge seam has a length that is longer than a length of the
centerline of the second envelope gore.
[0109] Method 1100 further includes the step 1114 of positioning a
final envelope gore having a first edge and a second edge adjacent
the first envelope gore, the step 1116 of sealing the second edge
of the final envelope gore to first edge of the first envelope gore
to form a final edge seam, and the step 1118 of adhering a final
fiber tape to a centerline of the final envelope gore, wherein the
final edge seam has a length that is longer than a centerline of
the final envelope.
[0110] As noted above, the adjacent envelope gores may be placed on
top of each other and an edge seam may be formed between adjacent
envelope gores by heat sealing a common edge of the adjacent
envelope gores. Furthermore, the steps of method 1100 do not need
to be performed in the exact order listed. For example, a number of
envelope gores could be attached together before the fiber load
tapes are attached to the centerlines of the respective envelope
gores. Alternately, the fiber load tapes could be applied to some
or all of the envelope gores before they are seamed together with
an adjacent envelope gore. Similarly, a number of envelope gores
could be lined up adjacent one another (rather than being stacked)
and seamed together. Or sections of the balloon envelope could be
formed and then the sections seamed together. For example, a first
section having of nine envelope gores could be formed and sealed
together with a second section having nine envelope gores. The
fiber load tapes could be positioned on the centerlines of the
gores at any point during the formation process.
5. Conclusion
[0111] The above detailed description describes various features
and functions of the disclosed systems, devices, and methods with
reference to the accompanying figures. While various aspects and
embodiments have been disclosed herein, other aspects and
embodiments will be apparent to those skilled in the art. The
various aspects and embodiments disclosed herein are for purposes
of illustration and are not intended to be limiting, with the true
scope and spirit being indicated by the following claims.
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