2 Responses to “HyperGravity”

1. admin says:

   November 30 at 12:23 pm

   David Quiroz (jsant…@vallenar.ing.puc.cl) wrote:

   : What is the HyperGravity ?

   "Hypergravity" in my research area means "more than one times the
   force of Earth’s gravity," usually caused by a centrifuge but
   occasionally caused by a rocket or a great, big planet (like
   Jupiter).  Airplanes also achieve a mild hypergravity state in the
   pull-out maneuver from a dive or a parabola.

   At NASA, we have a Zero Gravity Trainer aircraft, the KC-135, which
   is a modified Boeing 707 nicknamed the "Vomit Comet."  The KC-135
   is a four-engine turbojet.  We use it to fly parabolas to investigate
   the effects of "zero" gravity.  

   Investigators who fly experiments on the KC-135 must have a valid
   Air Force Class III medical, with NASA Physiological Training (which
   consists of an eight-hour training course and a high-altitude
   chamber run for hypoxia symptom training).

   The day before the flight, we conduct a Test Readiness Review.
   The investigators bring the hardware they’ll be flying on the
   "K-bird" to building 993 at Ellington Field, where safety inspectors
   review the documentation and each investigator gives a briefing on
   his experiment.  Typically, all the other investigators huddle
   around and watch each other’s briefings.  During the briefing, the
   investigator gives an overview of the experiment and the equipment,
   tells about the planned sequence of events, and describes how the
   equipment will be mounted inside the vehicle.  (Equipment must be
   mounted to withstand 9 G crash loads.)  The safety inspectors might
   ask questions about the medical effects of the procedures, or about
   how the wires will be run, etc.  They frequently give the investigators
   last-minute suggestions for improving safety or convenience of the
   experiment.  At the end of the inspection, the investigators are
   given a go/no-go, or are told what modifications need to be done
   before flight.

   Later that day, the investigators will have access to the aircraft
   to mount their hardware, install any wiring, and tap into the
   aircraft’s 120 VAC power lines.  

   The next morning, the aircraft is open at around 7 AM.  Investigators
   arrive, make any last-minute adjustments to their experiments, then
   go into building 993.  About 8 AM, there is a pre-flight safety
   video which reminds investigators about safety equipment and
   procedures.  After the video, the investigators don flight suits
   (if you don’t have your own, you’ll be issued one) and heavy boots
   (ditto).  Barf bags are handed out.  (The best place for a barf
   bag is in the pockets on your chest, sticking out a little bit,
   with the top open.  When the urge to hurl comes, it will come fast.
   You can see a picture of me with a jaunty-looking arrangement of
   handkerchief-like barf bags in
     http://sd-www.jsc.nasa.gov/folks/kjenks.html
   ).  Most of the investigators take their anti-nausea drugs, usually
   Scop-Dex, a mixture of scopalamine and dexadrine.

   About 9:30, the investigators start making their way out to the
   aircraft.  Ground support equipment (GSE) provides electrical power
   and (blessedly) air conditioning to the aircraft before flight.
   After a bit of milling around, the investigators take their seats
   at the rear of the aircraft, while Linda Billica and Bob Williams
   direct traffic and generally help out.  Dr. LaPinta takes his seat.
   The NASA videographers check their camera mountings (if any), and
   strap in.  Bob is the head of the team, Linda is his able assistant.
   Dr. LaPinta provides medical assistance before, during and after
   the flight.  There’s almost always a NASA photographer on board,
   sometimes two, for taking still photos and video during the flight.
   There’s a pilot and a co-pilot up front, but we investigators never
   see them.  

   The accomodations are spartan.  We investigators sit in military-style
   seats at the back of the plane.  There is one potty (but you don’t
   want to use it during zero-G).  There’s little air conditioning at
   the back of the plane, and the lighting is dim.  The investigators
   sit around and joke during taxi and take-off.  No in-flight meals,
   and Bob makes a crummy stewardess.  Dr. LaPinta has a supply of
   hard candy, which helps take your mind off your stomach.  Take-off
   usually happens around 10 AM.

   After departing Ellington Field (EFD) to the south, the plane flies
   out over the Gulf of Mexico, climbing to around 26,000 MSL (altitude
   above mean sea level), and 350 KIA (knots indicated airspeed).
   The yaw and roll autopilots are engaged, and the pitch axis autopilot
   is disengaged.  The pilot then pulls the nose up steadily to a
   maximum of 1.8 G, pitching up to 45-50 degrees.  The airspeed drops
   off.  The pilot pushes the stick forward and comes back on the
   thrust, taking the two outboard engines to idle, while the thrust
   of the two inboard engines control the fore/aft acceleration to
   zero.  The pilot watches the reading on the accelerometer, using
   miniscule control inputs to keep it at zero.  Over the top of the
   parabola, the pilot pushes the stick forward to hold the acceleration
   to zero.  The top of arc comes at 36,000 MSL, with 150-170 KIA.
   The pilot continues to pitch over until the aircraft is 45 degree
   nose down.  Thrust is steadily increased until back to 350 KIA, at
   which point the pilot pulls back on stick, bringing acceleration
   up to 1.8 G.  The maneuver ends back at 26,000 MSL, 350 KIA.  Wind
   from the nose or tail varies the parabola somewhat.

   During a flight, which lasts about two hours, total, we usually
   fly 40 parabolas.  In this aircraft (NASA has had several KC-135′s,
   each with the same tail number, NASA 930), we’ve done as many as
   101, depending on fuel and gross weight limitations.  More parabolas
   mean more flexing of the airframe and more stress.  We could fly
   200 maneuvers, but we’d use the airplane up.

   After the flight, we fly back to EFD, usually arriving around 12.
   We change out of our flight suits, and we talk about how our
   experiments went.  (We don’t usually talk about who got sick and
   who didn’t.)  The more adventurous (or more masochistic) go to
   Pe-Te’s Cajun Barbeque for lunch.  The investigators remove their
   equipment from the aircraft — it must be out by about 3 PM.  

   : if you know it, please send me e-mail to jsant…@vallenar.ing.puc.cl
   : thanks.

   Just because I’m feeling nice, I’ll send e-mail there, too, but it
   is generally poor manners to post a question to a newsgroup without
   hanging around to read the responses.

   – Ken Jenks, NASA/JSC/SD5, Space Biomedical Research Institute
         kje…@gothamcity.jsc.nasa.gov  (713) 483-4368

        "Good ideas are not adopted automatically.  They must be driven
          into practice with courageous impatience."
            – Admiral Hyman G. Rickover
2. admin says:

   November 30 at 12:23 pm

   For your viewing pleasure, I posted a couple of pictures and a
   description of a KC-135 flight on the General Aviation WWW server:
     http://aviation.jsc.nasa.gov/kc-135.html
   

   – Ken Jenks, NASA/JSC/SD5, Space Biomedical Research Institute
         kje…@gothamcity.jsc.nasa.gov  (713) 483-4368

        "The only way to make a difference in the world is to put ten
         times as much effort into everything as anyone else thinks
         is reasonable.  It doesn’t leave any time for golf or cocktails,
         but it gets things done."
            – Admiral Hyman G. Rickover