Hypersonic Inflatable Aerodynamic Decelerator (HIAD) technology is currently being considered for multiple atmospheric entry applications as the limitations of traditional entry vehicles have been reached. The Inflatable Re-entry Vehicle Experiment (IRVE) has successfully demonstrated this technology as a viable candidate with a 3.0 m diameter vehicle sub-orbital flight. To further this technology, large scale HIADs (6.0 8.5 m) must be developed and tested. To characterize the performance of large scale HIAD technology new instrumentation concepts must be developed to accommodate the flexible nature inflatable aeroshell. Many of the concepts that are under consideration for the HIAD FY12 subsonic wind tunnel test series are discussed below

Cassell, Alan M.

Swanson, Gregory T.

NASA Technical Reports Server

INSTRUMENTATION  DEVELOPMENT  FOR  LARGE  SCALE  HYPERSONIC  
INFLATABLE  AERODYNAMIC  DECELERATOR  CHARACTERIZATION
Gregory  T.  Swanson1,2,  Alan  M.  Cassell  2
1Santa  Clara  University,  Department  of  Mechanical  Engineering,  500  El  Camino  Real,  Santa  Clara,  CA  95053  USA
2[ERC  Incorporated],  Entry  Systems  and  Vehicle  Development  Branch,  NASA  Ames  Research  Center,  Moffett  Field,  CA  94035  USA
Background HIAD  Construction  Overview
Flexible  Aeroshell  PressureFlexible  Aeroshell  Deformation
Structural  Strap  Strain
Acknowledgments
Hypersonic Inflatable Aerodynamic Decelerator (HIAD) technology is currently being
considered for multiple atmospheric entry applications as the limitations of traditional entry
vehicles have been reached. The Inflatable Re-­‐entry Vehicle Experiment (IRVE) has
successfully demonstrated this technology as a viable candidate with a 3.0 m diameter
vehicle sub-­‐orbital flight. To further this technology, large scale HIADs (6.0 ? 8.5 m) must be
developed and tested. To characterize the performance of large scale HIAD technology new
instrumentation concepts must be developed to accommodate the flexible nature inflatable
aeroshell. Many of the concepts that are under consideration for the HIAD FY12 subsonic
wind tunnel test series are discussed below.
String  Potentiometers  and  Angular  Transducers
String  pots  teamed  with  angular  transducers  will  provide  2D  point  
tracking  on  the  HIAD  model  indicating  aeroshell  deformation.  
MEMS  Pressure  Sensors
Pressure  measurements  on  the  flexible  aeroshell  will  provide  modeling  
validation  while  varying  angle  of  attack.
Structural  Strap  Loads
Single  Axis  Load  Pins
Custom  Single  Axis  Load  Pins  from  NovaTech will  provide  load  
measurements  on  the  forward  and  aft  structural  straps.  
Challenges:
? Integrating  within  a  flexible  
substrate  (flexibility,  profile)
?Mitigating  measurement  errors  
due  to  pressure  port  design  and  
surface  roughness
? Peak  vs.  Valley  Measurements
Aerocover  Scalloping
Uni-­‐Directional  Bends  Sensors
Bend  sensors  will  be  employed  to  indicate  the  magnitude  of  scalloping  in  
the  aerocover  due  to  the  aero  loading.Data  Acquisition
Zigbee Wireless  Transceivers
To  mitigate  massive  wire  bundles  and  feedthroughs wireless  data  
acquisition  will  be  utilized  on  a  subset  of  the  sensors  systems.
Neil  Cheatwood,  NASA  LaRC
Steve  Hughes,  NASA  LaRC
Keith  Johnson,  NASA  LaRC
Anthony  Calomino,  NASA  GRC
Jeff  Brown,  ERC  Inc.
Dave  Bogdanoff,  ERC  Inc.
Glen  Brown,  HDT  Engineering  Services,  Inc.
Ben  Tutt,  Airborne  Systems  North  America
Rotary  SensorString  Pot
6.0  m  HIAD  Aft  View
MEMS  Pressure  Sensor
Design  Concepts:
? Right  Angle  Half  Grommet
-­‐ A  custom  designed  half  grommet  pressure  port  will
be  mounted  through  the  aerocover  to  provide  a  
repeatable  pressure  port  concept.    Then  pressure  
tubing  mounted  to  the  backside  of  the  port  will  run
to  the  MEMS  pressure  sensor.
? Pressure  Pocket  w/  Shim  Port
-­‐ A  custom  pressure  pocket  has  been  designed  to  
implement  a  protected,  low  profile,  flexible  pressure  
port.    The  pressure  pocket  is  formed  and  protected  by  
a  rubber  washer  on  the  backside  of  the  aerocover.    
This  pocket  is  sealed  using  RTV.  On  the  front  face  of  the  aerocover  a  machined  
metal  shim  acts  as  the  pressure  port.    Pressure  tubing  mounted  to  the  pocket  
runs  to  the  MEMS  pressure  sensor.
Challenges:
? 2D  measurements  required
? Integrated  sensor  system  
mounting  configuration
? Each  sensor  requires  
dedicated  power  regulation
? Test  hardware  mounting
High  Tension  String  Potentiometers
String  pots  will  be  used  to  measure  the  elongation  of  the  HIAD  forward  
primary  structural  strap.
High  Tension  String  Pot
Challenges:
?Measuring  strain  of  woven  materials
? Designing  a  flexible  low  profile  system  that  
allows  the  string  to  travel  unimpeded  under  
aero  loading  (mitigating  string  friction  and  
aero  loading  force)
Design  Concept:
? Teflon  Tube  Guide
-­‐ The  string  pot  line  will  be  guided  along  the  forward  primary  strap  by  
??????? ?????????????????????????????????? ????????????????????????????
pinching  due  to  aero  loading.    Friction  impact  will  also  be  mitigated  
by  employing  a  high  tension  string  pot  (116  oz).
String  Pot
Centerbody
Primary  Straps
Teflon  Tube  
Protecting  String
String  Pot  Anchor  Point
Structural  Strap  Strain  ConceptElongation  @  25o AOA
Aeroshell  Section  ?
Under  No  Aero  Load
Aeroshell  Section  ?
Under  High  Aero  Load
Aerocover
Bend  
Sensor
Flow
Aero  Skin  Scalloping  
Under  Load
Large  Scale  HIAD  Wind  Tunnel  Test  Series
Location: National Full-­‐Scale Aerodynamics Complex (NFAC) at NASA ARC
Primary Objective:
Characterize the 6.0 and 8.3 m diameter HIAD response to changes in dynamic pressures and angle of attack
over the range of expected flight conditions for a representative LEO re-­‐entry demonstration mission. The
HIAD test model ?????????? will be correlated to the structural simulation model. Measurements for model
correlation include inflatable surface displacement, surface pressures and structural strap loads.
Secondary Objectives:
? Determine a minimum inflation pressure needed to maintain structural stiffness and stability over the test conditions.
? Evaluate  the  HIAD  response  to  failure  modes  with  loss  of  torus  pressure.
? Evaluate  performance  of  developmental  instrumentation  and  pursue  embedded  flight  instrumentation.
6  m  HIAD  in  NFAC  40  x  80  Wind  Tunnel HIAD  Test  Hardware
Bend  Sensors
Challenges:
? The  aerocover  profile  must  be  known  to  
determine  the  magnitude  of  scalloping  (Each  
angle  of  attack  will  have  a  different  aerocover  
scallop  geometry)
? Relating  measurement  to  deflected  geometry
Design  Concept:
? Embedded  Deformation  Sensor
-­‐ Adhere  the  bend  sensor  to
the  back  side  of  the  
aerocover  in  between  
the  inflatable  toroids
to  measure  the    
scalloping.
Design  Concept:
? Teamed  String  Pot  /  Angular  Transducer
-­‐ To  accurately  depict  movement  in  a  2D  field  the  string  pot  will  be  teamed  with  an  
angular  transducer  to  measure  the  angle  at  which  the  string  pot  line  is  deployed.    
This  will  be  done  by  attaching  an  extension  bar  to  the  angular  transducer  that  
mimics  the  angle  of  the  string  pot.    This  sensor  system  will  be  mounted  at  two  
radial  locations  on  the  test  sting  to  monitor  aeroshell  deformation.
Sensor  System  Prototype
String  Pot
Angular  
Transducer
Extension
Bar
Line  Anchor
String  Pot  
Lines  on  
Model
Challenges:
?Mitigating  massive  wire  bundle  to  power  
and  monitor  the  100+  sensors
? Reduce  facility  costs  and  complexity  tied  
to  each  sensor  signal
? Long  Transmission  Distances
HIAD  Side  Profile  w/  
Aerocover
HIAD  Side  Profile  w/o  
AerocoverHIAD  Head  On  Profile  w/o  Aerocover
Aerocover
The  basic  HIAD  construction  consists  of  an  
inflatable  stacked  torus  mated  with  a  rigid  
center  body.    Loading  of  the  flexible  structure  
is  then  distributed  by  structural  straps  that  are  
anchored  to  the  centerbody.    An  aerocover  has  
been  included  for  data  measurement  
purposes.
Inflatable  Torri
Design  Concept:
? Wireless  Data  Acquisition
-­‐ Multiple  wireless  data  acquisition  nodes  will  be
implemented  to  mitigate  the  required  wiring  need  to  
monitor  the  sensors.      Each  node  will  transmit  to  a  base  station  located  in  the  
NFAC  T-­‐frame  that  will  convert  the  wireless  data  to  a  RS-­‐232  protocol.    Then  two  
RS-­‐232  to  fiber  optic  converters  will  be  employed  to  transmit  the  serial  data  
100+  ft  to  a  laptop  computer.
Structural
Straps
Centerbody
Port  View
Aerocover  Backside  
Sealed  Pocket  View
Pressure  Pocket  w/  Shim  Port
Pocket
Right  Angle  Half  Grommet
Notional  HIAD  
Port  Layout
Wireless  Node
Challenges:
?Measuring  flexible  material
loads
? Providing  a  similar  strength  
profile  as  to  the  solid  clevis  pins
? Characterizing  loads  on  both  the  
aft  and  forward  structural  straps
Dimensions  (mm)
Design  Concept:
? Strap  Load  Measurement  Pins
-­‐ The  HIAD  structural  straps  are  anchored  to  the  centerbody  by  integrated  clevis  
pins.    To  measure  the  loads  on  the  structural  straps  custom  designed  single  axis  
load  pins  have  been  designed  by  NovaTech.    The  load  pins  will  require  a  modified  
clevis  to  adapt  to  the  greater  pin  diameter  as  compared  to  the  standard  clevis  pin.    
These  pins  will  be  placed  at  selected  forward  and  aft  strap  mounting  locations.    
The  pins  will  then  be  monitored  by  the  NFAC  to  provide  real-­‐time  load  monitoring.
Single  Axis  Load  Pin
Load  Pins  Mounted  in  HIAD  Centerbody
Test  
Sting
https://ntrs.nasa.gov/search.jsp?R=20110014421 2019-08-30T16:23:36+00:00Z


Instrumentation Development for Large Scale Hypersonic Inflatable Aerodynamic Decelerator Characterization

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