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White Sands Missile Range - WSMR
High Speed Carrier
Project
Title: WSMR High Speed Aerial Cable Carrier
Project Customer: United
States Army / White Sands Missile Range
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WSMR Army Huey on High Speed Cable Carrier |
ACME SolidWorks™ Model
of Carrier Upper Frame |
Project Overview: The
development of a High Speed Aerial Cable Carrier (Carrier) for
White Sands Missile Range (WSMR) was initiated with a one page
statement of objectives, a verbal briefing by ACME identifying
a technical approach, and contract award. All the activities
occurred within 30 days.
WSMR has a test facility which consists of a 3 mile long high strength cable
strung between two mountain peaks. Test articles are attached to a carrier and
the entire assembly is pulled toward the higher peak along the cable to a predetermined
position. Once there, the carrier is released from its transport trolley and
accelerates down the cable due to gravity. This provides a moving target for
test scenarios. It passes through the test envelope and then decelerates and
stops before contacting the lower peak. During one of these tests, the cable,
carrier, and test article were inadvertently shot down and destroyed. As a result,
WSMR needed a replacement carrier to support future tests.
ACME Services Used: Mechanical
Engineering, Systems Engineering.
Project Details: The original carrier was designed as
a single use device which required extensive manhours and refurbishment
costs to prepare for an individual test. Additionally, it did not
function very well and did not provide repeatable results. ACME's
task was to design a robust, low maintenance carrier that could
withstand 250 knot speeds with a 20,000 lb payload. Additional
design requirements included a vibration suppression system, extensive
on board instrumentation including video recording and GPS, and
large power sources for the test article.
Another major design requirement
was an efficient method of attaching the carrier to the cable.
One of reasons that this project was notable was that there was
no design precedent. When designing trainers, ACME uses lessons
learned from previous programs. In developing the carrier, ACME
had no precedent. Consequently, the development of the carrier
exclusively depended on engineering analysis.
At program initiation,
ACME immediately began a systematic systems engineering analysis
of the problem. This analysis identified a variety of derived requirements
and began bounding the physical constraints of the carrier. For
example:
a) It had to withstand rocket thrust acceleration to achieve
the 250 knot speed
b) It had to have redundant braking
systems – both disk
brakes on the carrier wheels and a parachute
c) It had to have the
ability to put a reverse bend in the cable as it passed through
the carrier to increase friction high enough to allow braking
d)
The carrier could not damage the cable during operation (the cable
costs in excess of $1M)
e) The installation of the carrier on the
cable should not take more than 1 hour instead of the day and a
half that it took to install the old carrier.
f) The carrier had
to have a compound suspension at both the front and the rear in
order to distribute the weight of the carrier and its payload equally
among all the upper carrier wheels along the varying catenary angle
of the cable.
After the carrier-derived requirements were better
understood, ACME immediately began the hardware and software engineering
necessary to design and develop the carrier. The software effort
was concerned with development of a carrier instrumentation and
control system. The hardware effort involved design of the structure,
extensive finite element stress analysis, and development of
the fabrication drawings. Finally, ACME initiated a parallel
effort to develop acceptance test procedures and operating manuals.
The carrier components were fabricated and assembled in the ACME
shop. The resulting carrier design produced a device approximately
30 inches wide, 25 feet long, and 5 feet high. The top of the
carrier was hinged and opened like a box so that it could be
efficiently hung on the cable (it now takes about 20 minutes
to attach the carrier to the cable). A pneumatic system is used
to energize the vibration suppression bladders and to introduce
the cable reverse bend. A blow down hydraulic system is used
to control the disk brake system on 9 of the 13 carrier wheels.
The carrier has dual on-board motor generators and a battery
backup system to power the test article and on-board instrumentation
and control system. Furthermore, the carrier has excellent equipment
access and integral work platforms to facilitate field support
of the carrier equipment.
ACME accomplished the design and development of the carrier in less than six
months. The carrier was then relocated to the White Sands site where its operation
was characterized (final acceptance testing). In short, the carrier exceeded
all expectations. It was simple to attach to the cable, the vibration suppression
system worked well, the braking system was reliable, the carrier aerodynamics
showed that the new carrier was 17% faster than the old carrier under the same
conditions, and, most notable, the carrier performance was highly repeatable
with less than a 1% variation between standard runs. In fact, the carrier was
so successful, WSMR ordered a second carrier and an ancillary equipment pod which
attached to the bottom of the carrier.
Delivery Date: January,
1999
Customer Comments: N/A
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