reentry f experiment

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NATIONAL AERONAUTICS AND SPACE ADMINISTRATION TES WO ?-41t5N E W WASHINGTON, D.C. 20546 WO 3W-625

FJR RELEASE: FRIDAY P.M.April 19, 1968

RELEASE NO: 68-68

REENTRY F EXPERIMENT

A f l i g h t experiment in aerodynamic heat ing a t speeds up

to 13,500 miles-per-hour wil l be launched Apr. 25 by th e

National Aeronautics and Space Administration from Wallops

Sta t ion , Wallops I s land , Va.

Purpose of th e experiment, known as Reentry F, is to

measure heat transfer in a slender cone at hypersonic

speeds for comparison with ground studies. Scientists

are unable, even with the best available laboratory facilities,

to simulate al l at once complex variables governing aero-

dynamic heating. For that reason flight experiments ar e

needed to provide a basis for useful ground test results.

The objective is to obtain in flight fundamental research

data on aerodynamic heating and th e t r ans i t ion from laminar

(smooth) to turbulent flow in th e boundary layer.

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The payload ofReentry F is a graphite-tipped beryllium

cone 13 feet long, tapering from 0.1 inch a t the nose to 27.3

inches at the base. When it separates from the rocket third

stage, the cone and its internal instruments will weigh 600

pounds. It will be launched on a Scout rocket.

The experiment was designed by NASA's Langley Research

Center, Hampton, Va. Reentry F is the sixth flight in a re.

entry heating series sponsored by the Office of Advanced Re-

search and Technology (OART).

Fo r this experiment, three of th e Scout's four stages will

be used. Two will fire on the ascending portion of the flight

trajectory, and the third will drive the instrumented payload

to hypersonic speeds after it has passed its apogee (highest

point) and is descending into the atmosphere.

Aerodynamic heating, the phenomenon which causes a meteor

to flare as it streaks into the Earth's atmosphere, is rea-

sonably well understood in relation to flight of high speed

aircraft, missiles and spacecraft. Much research and engi-neering has been done to protect flight vehicles against its

effects -a heat sh ie lds of manned spacecraft owr

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Th e less familiar term "boundary layer" refers to the

layer of air close to the surface of a moving object in flight.

The moving object carries a very thin sheet of air molecules

held to it s surface by friction. These molecules rub against

their neighbors, generating heat which increases as speeds go

higher.

When the molecules nearest the vehicle surface slidesmoothly over their closest neighbors, the boundary layer is

said to be "laminar" or smooth. Designers would prefer to

have smooth attached boundary layers over the entire surface,

fo r they reduce air friction (drag) and heating.

The boundary layer is sensitive to many factors Including

speed, pressure, vehicle shape, surface roughness and tempera-

ture. Instead of remaining smooth, it frequently begins a

churning or turbulent motion, and the "scrubbing" action in

th e turbulent zone greatly increases aerodynamic heat ing.

When th e fac tors which cause turbulent boundary layers

and higher heat ing rates are more thoroughly understood

through research, designers of m a n y types of hypersonic ve-

hicles will benefit by being be t t e r able to promote or pro-

long smooth, laminary boundary layer conditions.

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Transition from laminar to turbulentboundary layers

sometimes can be observed in a column of smoke ascending from

a chimney into still air. Smoke will rise smoothly and un-

disturbed for a considerable distance, then at some point it

will begin churning and billowing, which signals turbulent

flow,

The slender cone-shaped spacecraft selected for the Re-

entry F experiment is expected to develop turbulence from about

two feet behind its sharp graphite tip down to its base. In

that area turbulence in the boundary layer should result in

measurably higher rates of heating.

The results of the Reentry F experiment will be useful

in designing hypersonic aircraft, lifting entry vehicles,

slender missiles and other advanced vehicles. Reliable date

and a theoretical basis for aerodynamic heating

analysis are required for efficient design.

REENTRY F SPACECRAFT

Since heating rates are of the prime interest, th e

entire outer shell of the Reentry F spacecraft is a beryllium

calorimeter or heat measurement device. It consists of seven

segments, each 0.7 inch thick. Near its base are 81.x quartz

antenna windows. The graphite nose tip is 7.5 inches long.

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Embedded in the beryllium calorimeter segments are 21thermal sensors, each having four thermocouples located at

different depths. Four more thermal sensors are mounted on

the base cover, an d 13 pressure ports are located along the

conical shell and on the base to verify the predicted pressures.

Within the conical shell and separated from it except

fo r a minimum of attachment points is a cylindrical package

fo r instruments an d power supply. The separation is essential

ti o assure accurate aerodynamic heating measurements by the

calorimeter.

The package contains a telemetry transmitter an d it s

associated electronics, accelerometers, gyros, a tracking

beacon an d the necessary power supplies. Telemetry will be

transmitted throughout the flight and playback is no t neces-

sary because no significant signal attenuation (blackout) is

expected during the reentry.

Th e payload and backup were built by the General Electric

Company's Re--entry Systems Department under contract to the

Langley Center, which is managing the reentry project.

LAUNCH VEHICLE AND FLIGHT PLAN

A three-stage Scout will launch th e Reentry F Experiment

to reenter a heavier than normal spacecraft at a sub-orbital

velocity of 13,500 mpn.

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The first two stages provide boost and coastto an

apogee altitude of about 115 miles. The Scout guidance

system orients the vehicle to its desired reentry angle

of 20 &egrees below the horizontal, On the descending leg

of the trajectory, the third stage ignites at about 100

miles altitude.

Before separation of the spacecraft about 55 miles aboveEarth, a pair of small rocket motors will ignite to give it aspin rate of about 55 rpm and a speed of 13,500 mph. Theprimary data period of the experiment will begin at 21 milesand will continue until the calorimeter begins to melt around10 miles altitude. The payload will impact in the Atlantic

Ocean 140 miles northeast of Bermuda,some 800 miles from

Wallops Island.

TRACKING AND DATA ACQUISITION

Radar, telemetry and optical coverage will all play apart in gathering detailed information on the flight of Re-

entry F.

Primary telemetery stations are Bermuda and the WallopsStation telemetry ship Range Recoverer. Radar data will begathered by Bermuda and an Eastern Test Range radar ship

Twin Falls Victory. Two NASA aircraft flying northeast ofBermuda will provide optical observations and additional

telemetry coverage.

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Tracking to apogee will be accomplished from Wallops,

and the Bermuda Station will track the payload into the re-

entry area.

Atmospheric density and temperature measurements will

be made by ARCAS sounding rockets launched from Bermuda be-

fore and after the flights, supplemented by weather balloons

from Bermuda and the Range Recoverer.

Total darkness and no more than one-quarter local cloud

cover in the reentry area are required to assure optical

coverage of the flight, so launch windows occur at night.

SCOUT REENTRY HEATING PROJECT OFFICIALS

Following are the key off ic ia ls fo r the Scout Reentry F

Project:

Reentry F Experiment - Langley Research Ccnter

Eugene C. Draley, Assistant Director for Flight Projects

E. C. Hastings, Project Manager, Reentry F

James L. Raper, Assistant Project Manager

Howard S. Carter, Experimenter

John N. Daniel, Tracking and Data Acquisition

Scout launch Vehicle

R. D. English, Head, Scout Project Office

B. Leon Hodge, Operations Director

Robeic A. Schmitz, Payload Coordinator

E. Eugene Hall, Systems Integration Engineer

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Wallops Station

Robert T. Duffy, Test Director

Tom W. Perry, Jr., Project Engineer

NASA Headguarters

W. A. Guild, Chief, Space Flight Projects, OARTP. J. DeMeritte, Technical

Associate, Reentry FExperiment, OART

J. Levine, Project Officer, Reentry F Project, OAR'

P. E. Goczh, Manager, Scout Program, Office of Space

Science and Applications

General Electric Cmrnpany

E. W. Richardson, Manager, Reentry F Program

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reentry f experiment

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