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REPORTS

MAGNETIC CONTROL ASSEMBLY

CONTRACT No. NAS 5-21867

REPORTS

MAGNETIC CONTROL ASSEMBLY

CONTRACT NAS 5-21867

1. Performance of Nimbus/ERTS MCA

2. Control Laws for Proposed MCA for Nimbus

3. Electromagnet S/N 15026 Test Results

4. MCA Design Data

5. Operational Amplifiers, High Impedance with Small Resistors

6. Mounting Orientation of ITHACO's MCA and Schonstedt'sMagnetometers. MCA Magnet Polarities

7. MCA Preliminary Design Review Meeting - GSFC(9-12-72)

8. Thermal Vacuum Test Plan for the Qual Model MCA andThermal Test Plan for Magnetometers (Schonstedt's)

9. RMP Polarities

10. Qualification Test Report of Magnetic Control AssemblyS/N PR1

ITHACO, Inc. 735 W. Clinton Street Ithaca, New York 14850

April 25, 1972File: 10-2724Report No. 90420Approval ,<2i

TO: R. Z. Fowler

FROM: A. C. Stickler

SUBJECT: Performance of Nimbus/ERTS MCA

This report contains preliminary results of the MCAperformance under the conditions stated on the attached curves.In all instances an initial condition in pitch is inserted toshow the transient and damping performance.

Figure 1

Unloading performance with the attitude control systemoperating normally. Peak excursions of the wheels are:

Roll - 35 RPMPitch - 5 RPMYaw - 50 RPM

This assumes perfect attitude control via the wheels and doesnot include second order effects such as tach imperfections.

Figure 2

Pitch control performance when the pitch wheel has failed.The peak steady state pitch error is shown to be negligible.

Figure 3

Yaw control performance when the yaw wheel has failed.The performance shown should be regarded as the best possibleunder the stated conditions because of the simplifying assump-tion that yaw information is perfect. This curve says that,insofar as corrective torque availability is concerned, theyaw error can be limited to 10. Additional runs will be madewith the real yaw sensor (RMP) simulated.

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May 9, 1972File: 10-2724Report No. 90433Approval/ -27i=

TO: R. Z. Fowler

FROM: R. L. Graham

SUBJECT: ELECTROMAGNET S/N 15026 TEST RESULTS

A 7-inch electromagnet was tested in the MMCA TestFixture by measuring coil voltage vs coil current vs magneticmoment.

This magnet gives a moment/coil voltage slope of 388p-cm/Vand a moment/coil current slope of 87.6p-cm/mA with linearoperation extending to about 7000 p-cm. The residual momentafter applying 24V d.c. to the coil was about 15 p-cm.

The test setup consisted of a 10 ohm, 0.1% meter shuntin series with the magnetizing coil and connected to a d.c.supply. A DVM (GP47) was connected directly across the mag-netizing coil and a digital multimeter (VM30) across the 10 ohmshunt. A Sperry Magnetometer (GP20) was held at 44.5cm spacingfrom the magnet under test by the MMCA Test Fixture.

The electromagnet core was 0.28" x 0.28" x 7" alloy 48with a magnetizing coil consisting of 10,519 turns of #32 AWGdouble formvar copper wire in 15 turns.

Bridge measurements gave 224 ohm coil resistance and5.725 Henry inductance.

cc: V. Selby

Report No. 90433Page 2

PRECEDING PAGE BLANK NOT FILMED

CoilVoltage (V)

0

-0.519

+1.459

+2.079

+3.033

+4.016

+5.152

+6.625

+7.045

+8.007

+9.061

+10.025

+11.08

+12.03

+13.06

+14.11

+15.15

+16.13

+17.01

+18.05

+19.00

+20.16

+21.48

+22.05

+23.00

+24.11

+9.056

- 0

-5.031

-10.085

CoilCurrent(mA) i

0

-2.3

+6.5

+9.4

+13.7

+18.1

+23.2

+29.8

+31.7

+36.0

+40.8

+45.1

+49.7

+53.9

+58.3

+62.9

+67.5

+72.1

+75.7

+80.3

+84.8

+89.8

+95.5

+97.9

+102.0

+106.7

+40.1

0

-22.3

-44.7

MagneticMoment (p-cm)

-3

-225

+550

+800

+1200

+1580

+2000

+2600

+2720

+3120

+3500

+3900

+4300

+4700

+5100

+5400

+5800

+6200

+6500

+6850

+7200

+7430

+7786

+7820

+8000

+8100

+3500

+15

-2000

-3900

Report No. 90433

Page 3


May 8, 1972File: 10-2724Report No. 90429Approval /.2-/=

TO: Peter Hui -

FROM: A. Craig Stickler

SUBJECT: Control Laws for Proposed MCA for Nimbus

In a recent memo (ITHACO Report No. 90417, 4-20-72) Idiscussed a simulation model suitable for investigation of thesmall angle attitude dynamics (and associated control systemdynamics) of a satellite in a circular orbit. In this memoI will discuss some recent development work on a proposedauxiliary attitude control system suitable for the Nimbus/ERTSseries satellites. This work uses that model.

The proposed system (termed a Magnetic Control Assembly,MCA) consists of three 5000p-cm electromagnets, a three-axisSchonstedt magnetometer and associated control electronics.The system performs two separate functions. In the course ofnormal operation of the primary attitude control system, theauxiliary system serves to unload excess momentum from themomentum reaction wheels by torquing against the Earth's magneticfield. In this way the reaction wheel speeds are constrainedto a narrow range about some operating points. This eliminatesthe consumption of gas and provides better attitude control.

In the event of a failure of either or both of the pitchor yaw reaction wheels, the proposed system simultaneouslyperforms another function - that of attitude control itself.This it does again by magnetic torquing against the Earth'sfield in response to attitude error signals from the rollscanner pair. Both of the above functions are accomplishedwithout the need for mode switching or external commands. Justhow this is done will be developed shortly. On the basis ofsome initial simulation work we have some performance predic-tions for this system. These predictions are recorded in ITHACOReport No. 90420, (4-25-72), a copy of which accompanies thisreport.

In summary we can say the following. During normal opera-tion the peak excursions of the primary control system reactionwheels were: Roll -, 35RPM, Pitch - 5RPM, Yaw - 50RPM. Whenthe pitch wheel wastdeleted (simulating pitch wheel failure) wefound that the maximum steady state pitch error was of theorder of 0.1 degrees. When the yaw wheel was deleted the peakyaw error was about 1 degree. The parameters and details uponwhich this simulation and these results are based were as follows:

Report No. 90429

PRECEDING PAGE BLANK NOT FILMED Page 2

(1) Disturbances were 2000p-cm magnetic unbalance on thepitch and yaw axes.

(2) Perfect yaw, roll, and pitch information is assumed.

(3) A tilted dipole model of the Earthl field is used.

(4) A 600 nautical mile circular orbit is assumed.

(5) Nimbus "E" parameters are incorporated in the simula-tion model.

The plots accompanying the referenced report (ITHACOReport No. 90420) offer a more complete picture of systemperformance. Of particular note is the excellent pitch per-formance. The pitch excursions are of the same order as ourability to measure pitch. Further, they are about equal tothe deadbands in the pitch pulse modulator. This means it ispossible (likely, for the greater part of the time) that thepitch wheel will not be driven. We could then expect a pro-longation of the life of the wheel and a savings of the powerit normally uses. It is quite possible that the measured pitcherror could be reduced somewhat; we have simulated the controlscheme with only one set of gains, parameters, etc. and haveby no means settled on the best combination.

MCA CONTROL SCHEME

Let us consider a possible wheel unloading scheme. Thecoordinate notation used in this discussion is

yaw - axis 1 - ~ - radially outward

roll - axis 2 - - forward into orbit

pitch - axis 3 - e - along the orbit normal.

This astrodynamic coordinate system is of course right F

handed (yaw x roll = pitch).

Now, the excess momentum to be unloaded is I

he = 6hlel + 6h 2 e2 + 6h 3 e 3 (1)

where the 6hi are the individual wheel momentum offsets (6 wiIW),and the ei are unit vectors. The torque available to unloadthis momentum is given by

T = M x B = Tle1 + T 2 e 2 + T3 e 3 (2)

T1 = M2 B 3 - M 3B 2

T2 = M3B 1 - M 1 B 3

T3 = M 1 B 2 - M2B1

X "''X'tL

Report No. 90429page 3

These torque components should be opposite in sign to theexcess momentum components given by (1). Note, however, thattwo Mi are involved in determining each Ti , and conversely,each Mi enters into two Ti . What this means is that any par-ticular Mi, say M2, may help by unloading on one axis while atthe same time acting detrimentally on the other axis. In orderto minimize the ratio of such undesirable effects to desiredaction, the following scheme is employed. Each Mi is scaledso that it becomes greater as the amount of desirable effectincreases over the undesirable effect. There are many ways toimplement such a general concept, and the one which we havechosen is

M1 = 6h2B3 - 6h 3 B 2 (3)

M2 = 6h 3 B 1 - 6hlB3

M 3 = 6hl B2 - 6h 2 B 1

This scheme was chosen with both ease of implementation andsuitability in mind. The "net good" (or harm) that each Miwill cause is evaluated as the sum of two terms, correspondingto the two axes about which it yields a torque. Each term isproportional to the product of the momentum correction required(6hi) and the field component (Bi) available to make that cor-rection. The sign for each term is appropriately chosen. Notethat the "net good" or effect of each Mi must be greater thanor equal to zero. If the amount of desirable over undesirableeffect is small, then the Mi is small. Equations(3) may besubstituted in (2) to yield

T1 = -(6hl)(B2 + + B B 2 6h2 + BlB 3 6h 3(4)

T2 = -(6h2 )(B2 + B3) + B 2 B 3 6h 3 + BlB26hl

T3 = -(6h 3)(B2 + B2) + B 2 B 3 6h2 + B 1 B 3 6hl

In each of (4), the first term on the right is the desired one;the other two are of the "noise" category. Each equation is ofthe form (since Ti = d(6hi)/dt)

x =-Kx K = (B? + B 2) 2 0 (5)

which indicates exponential decay of the excess momenta. Notethat there is undesirable coupling as indicated by the secondand third terms in each of (4), but its sign varies and itshould not prove to be a problem.

..

Report No. 90429Page 4

We have so far discussed how momentum unloading is to beaccomplished; now we turn to position control. Instead of goingthrough a long discussion of how we came upon the present scheme,we will merely exhibit it and discuss its operation. The schemeis as follows. Everywhere in (3) where 6h i and 6h3 appear, wesubstitute (6hl + all + B1i) and (6h3 + a38 + B36), respectively.The a and 8 are appropriately chosen constants. These terms thenobviously replace the 6h

iin (4).

Ignoring the cross coupling terms in (4), the equations forp and 0 are

(T 1 = I1i) + K6hl + K 14i + Kalc = 0 (6)

(T2 = I20) + K6h3 + KB38 + Ka38 = 0

K = (B? + B?) > 0

Now, these equations are those of a damped second order system.In the event of a yaw and/or pitch wheel failure, 6hl and/or6h 3 goes to zero and the corresponding attitude angle comesunder magnetic control. Under normal operating conditions P, P,0, and b are quite small and their presence in the magnet controllaw (3) does not affect the unloading scheme. The control lawnow appears as

M1 = G[(6h2 )B 3 - (6h3 + g30 + a 3 0)B2] (7)

M2 = G[(6h3 + 030 + a30)B1 - (6h1 + B1i + alf)B 3]

M3 = G[(6hl + l14 + alf)B2 - (6h2 )B 1]

G is an overall gain factor. In some initial simulation workwe have set G = 70 (MMa ), so as to drive the magnets full on fora 6hi = 0.05 (lb-ft-sec) and Bi = 0.3 (Gauss). That is of course,assuming only one term in each of (7) is active. Also, in thissimulation we have obtained reasonable performance for at = a3 =10, corresponding to full on magnets for V or 0 = 0.005 (radians),and 81 = B3 = 270, corresponding to full magnets at ~ or 0 = 0.0107(deg/sec). These parameters are those which were used for thesimulation work reported in ITHACO Report No. 90420, referencedearlier in this report.

The above description, in conjunction with the referencedsimulation study, indicates how a satisfactory momentum unloadingscheme and auxiliary yaw and pitch attitude control scheme may beeasily implemented, without mode switching and with a minimum ofhardware. In all of the above the type of operation is that whichwe term "Mode 1". This is the normal operating mode. We note in

Report No. 90429page 5

passing that a second mode, utilizing momentum bias, is availableshould the yaw gyros (RMP's) fail. In that case, we must relyon quarter orbit coupling for yaw control, hence the need for amomentum bias (dual spin) system. Ground commands are necessaryto initiate this mode, because the control laws are somewhatdifferent, etc.

The details of Mode 2 operation will be the subject of asubsequent memo.

6y ad'bayDistribution:M. Lidston, NASAS. Kant, NASAR. FowlerM. RutkowskiJ. KenneyD. Sonnabend


August 4, 1972Report No. 90483File: 10-2724

Approval Z'?c /

TO: Seymor Kant Ps 6Peter Hui

FROM: A. C. Stickler

SUBJECT: MCA Design Data

Here are some copies of my notes detailing the MCAconfiguration and gains. Also included is the rationalfor setting these gains from the points of view of per-formance, noise, offsets, etc.

Most of the above we discussed and agreed on ingeneral form last Monday (7/31/72) in conference with you.

Included with these notes are my feeling as to thesimulation work required. This should commence next week.

I apologize for the hand written design calculations,but our secretary is leaving and I thought you would preferto have this information now, rather than having themtyped later.

i, c:.b

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I August 22, 1972

Report No. 90492

Operational AmplifiersHigh Impedance With Small Resistors

Occasionally, when using operational amplifiers in highimpedance circuits, the need arises for impractically largevalues of resistors in the feedback circuit. By using a T-net-work in the feedback circuit, the desired effective feedbackresistor may be achieved without using super large resistors.

Consider the following circuit:e

~8-- R2)91~- R3T ~~~~t

'4

.5RFeedback

Gain =- RR5

I1 t

It may be shown, using the usual operational amplifierapproximations, that RFeedback is given by:

RFeedback= R2 + R

3+ R 2 R 3

R4

For instance, if R2 and R3 are 500k and R4 = lk, then

RFeedback is 251 Megohms. Of course, care must be exercised

to be sure not to run out of open loop gain.

An important question is:

What is the effect of offset and bias currents?

II is a bias current. Then I1 = I2+I5+A where A is

an offset current. Let ei=o.

.elI1 = R1

e2-el12 = R2

eo-e 2

I3 R3

-e 2

14 R4

I. _.15 - R5

I2= I3+I4

C

Page 2August 22, 1972File No: 90492

Thus

e2-el e0 -e 2 e2

2 3 R4

-el e 2 -el e1

- -+ AR1 R 2 R5

To have eo=O for any bias current is desirable. Set

eo=O and A=o and solve for R1

The proper choice for R1

is:

R5 (R2R4R+R3R4+RR3)1 R R +R3R +R R +R2 R+R43R

It may be shown that this result is equivalent to:

1 1 1

R 1 R5 R2+R

3R4

R3+2R4

In general, then eo is given by:

e0 = R 3 1 R2 R- R 4 ) ( 2 3 + e

R 2

With the proper choice of R1, the e1 terms sum to zero.

e e =-A R R + 1+

-A (R 2+ R 3+ R 4

= -A RFeedback

Thus, to adjust gain, the effective feedback resistor is given by

R2R3fb = R2+R3 R

4

Page 3

August 22, 1972

R1should be chosen to be equal to the parallel com-

bination of

R5 and R2+ R3 R4

R3+R4Obviously _R3R4 is the parallel combination of

R3+R4

R3 and R4

The offset currents flow through the effective feed-back resistor, Rfb

cc: R. ShenR. GrahamJ. Langm.'W. HennigerD. ChandlerO. KapasiP. CostantiniH. Jorgensen

Ithaca, New York- 14850

I

Report #90505Project MCAFile: #10-2724August 30, 1972Approval: r-- --

Ennio Scopel (GSFC)

FROM: Robert Shen

SUBJECT: (1) Mounting orientation ofITHACO's MCA and Schonstedt'sMagnetometers.

(2) MCA magnet polarities

(1) The ITHACO MCA package and theSchonstedt Magnetometer packageshould be mounted in an orientationas shown in Figure 1.

TO:

ITHACO, Inc. 735 W. Clinton Street

.(2)

orbit directionFig. 1

(2) The MCA magnets will be energized asshown when the following voltagesappear. across their windings. See"Function Block Diag. MCA F50030"

PositiveA5Jl-lA1J2-23A5J1-25

NegativeA5J1-2A1J1-4AlJ2-1

RollYawPitch

..

Report #90505File: #10-2724

August 30, 1972Page 3

This is the same as when r

in Roll, B , = negative;

in Pitch, B0 negative;

in Yaw, B, = negative;

during acquisition.

This is also the same as when

in Roll, (6w4 + f)B0 - (6w0 + 0)Bg, = negative;

in Pitch, 6wB$ - (6w4 , + fI)B4 = negative;

in Yaw, (6we + 0)B , - 6wBe = negative;

during orbit mode.

Distribution:Ennio Scopel (GSFC)Peter RHi (GSFC)Bob Fowler (ITHACO)Mike RutkowskiDave SonnabendBob ShenCraig Stickler

AITIACO, Inc. 735 W. Clinton Street Ithaca, N.Y. 14850

Report #90519File #10-2724September 13, 1972Page 1

To: Distribution

From: M. Rutkowski

Subject: MCA Preliminary Design Review Meeting - GSFC (9-12-72l

Attended By: NASA H. NeumanG. BranchflowerH. DamareP. HuiD. Murray

GE S. MillmanW. RichmondB. Siegel

ITHACO C. SticklerR. ShenM. Rutkowski

Action Items

1. Prepare a qualification test plan for MCA S/N PR1 to be fully compliantwith requirements of GSFC Spec S-320-NI-4.

Shouldconsist of the following:

A) Vibration - MCA & Probe

1. Define levels

2. Define tests to be performed pre and post vibration

3. Specify power off during vibration

4. Specify axes of orientation

5. Define visual post vibration inspection - solder

cracks, loose screws, etc.

6. Define test fixture to support both MCA & probe

7. Define which external connectors should be presentduring vibration and how they should be supported.

Report #90519File #10-27.24September 13, 1972Page 2

B) Thermal vacuum

1. Define time/temperature profile for each box

2. Run MCA in vacuum and probe in thermal chamber.

3. Define tests to be performed prior to, at eachplateau, and subsequent to TV test.

4. Define vacuum levels required.

Action: R. Shen Due: 9-15-72

2. Prepare a vibration and a thermal vacuum test procedure.

Responsibility: R. Shen Date Reg. 9-19-72

3. Design and fabricate vibration fixture to be compatible

with GSFC shaken hole pattern.

Action: R. Fleming, S. Rustyak Due: 9-21-72

4. Design and fabricate TV chamber harnesses and heat sink/insulator for mounting MCA in chamber.

Action: S. Rustyak Due: 9-22-72

5. Obtain flight and qualification test history on SchonstedtMagnetometer and submit to G. Branchflower.


6. Perform simulation to determine the effect on MCA performancein the presence of fields of 25 and 50 mg. This is requiredin order to determine how close the MCA can be placed to theRBV shield.

Action: C. Stickler Due: 9-22-72

7. Submit to GSFC a summary of changes contemplated that willmake MCA S/N FT 1 different than PR 1, e.g. layout changes,off pad soldering, separate relay grounds, etc.

Action: J. Gosart Due: 9-22-72

8. Update FT 1 parts lists and prepare NASPAR's for all items,Ithaco and Schonstedt, not on GSFC PPL-11.

Action: J. Gosart Due: 9-22-72

Report #90519File #10-2724September 13, 1972Page 3

9. Add TLM for MCA on/off status. Use separate -24V to be pro-vided on TLM connector.

Action: R. Shen Due: ASAP

10. Send copies of MOPS and RQPS for soldering potting andconformal coating to GSFC.

Action: S. Rustyak Due: ASAP

11. Place orders for all parts not already bought for 3 MCA's.


12. Prepare test procedure then perform test on MCA PRt with.Eng Model CLB to demonstrate interface compability.


13. Ensure that potting of intercard harness connectors andepoXying of large capacitors is included in MOPS and flowchart.


14. Crimp and pot Schonstedt probe connector as well as all othermating interface connectors to be vibrated, e.g. power, TLM, etc.

Action: S. Rustyak Due: 9-15=72

15. Change Schonstedt Procurement Spec. to specify the newtechniques in solderingconformal coatingand connectorcrimping and potting.


16. Add to flow plan card photos showing conformal coatingand potting.


17. Schedule deliveries of flight units as follows:

FT 1 -------- 15 Jan 1973FT 2 -------- 1 May 1973FT 3 -------- 15 Aug 1973


Distribution: Attendees: S. Rustyak-R. Fowler J. GosartR. Fleming V. Selby


j Report #90526File No. 10-2724

Sept. 18, 1972Page 1Approval: -. X

To: G. Branchflower

From: R. Shen

Subject: Thermal Vacuum Test Plan for the Qual Model MCAand Thermal Test Plan for Magnetometers (Schonstedt's)

TABLE OF CONTENTS:

1. Brief discussion on test plan

2. Vacuum level and pump down time

3. Temperature cycle profile and tolerance for Qual MCA andMagnetometers

4. Tests performed as indicated on the temperature cycle profile

5. Outputs of MCA monitored on chart recorder when tests are notperformed.

I

Report #90526Page 2

1. Brief discussion on test plan

The MCA will be tested inside the Thermal Vac oven

throughout the test. The Magnetometers will be tested

in an oven or at room temperature outside the Thermal Vac chamber

according to the temperature profile shown in Section #3.

2. Vacuum level and pump down time

The Thermal Vac chamber shall be evacuated to the pressure

of 10-

5 mm Hg or less in a period of more than 4 hours. This

rate is much slower than the actual flight conditions. This

pump down will be done with the oven at 500 C. Then the oven will

be brought back to room temperature. The Thermal Vac cycle

will start from there.

3. Temperature cycle profile and tolerance for Qual MCA and Magnetometers

See Figure 1.

The Thermal Vac Temperature profile is from S-320-NI-4

Nov. 1, 1968, Attitude Control Subsystem. The temperature

tolerance is ± 30 C. The temperature cycle for the Magnetometers

is agreed upon with GSFC. MCA subsystem tests ATPS 1105 for

high and low temp will be run at the high and low temperature

plateausas specified in the test procedure. At the intervals where *'s

are marked, the magnetometes will be excited and their output

recorded. See detailed test plan in Paragraph 4.

During the period not covered by the tests mentioned

above, Telemetry outputs will be monitored on an eight channel

recorder as specified in Para. 5.

4. Explanation of tests indicated on the temperature cycle.

a) ATPS 1105. This is the system level test. It involves

plotting the magnetic moment (actually voltages applied to

magnets) varying one of the following and holding the others

constant B yaw, B pitch, B roll, pitch error, yaw error,

pitch yaw and roll tach.

b) The-following paragraph of ATPS 1105 will be performed at

the beginning of the cycle. (Vacuum at room temp).

(Para. 6.1, 6.4, 6.5.11, 6.5.13, 6.5.21, 6.5.25, 6.5.36, and 6.5.37).

Report #90526Page 3

c)* For this test, the Schonstedt magnetometers will

be placed in a zero magnetic field enclosure (nested shield).

And electric coil will be placed alongside with the magne-

tometer in a fixed orientation such that when it is energized,

all three magnetometers will receive magnetic fields. This

whole package will be placed inside an oven(for temperature

test).

When the desired temperature is reached and stabilized

for three hours the coiled will be energized with a fixed

current l)in one direction, 2) then the opposite direction

and 3) then turned off. In all three cases, the B fields

and their polarities will be recorded. The -24 volt current will

also be recorded.

d) If for any reason the tests in 4 a) or c) cannot be

finished during the 48 hours Thermal Vac plateaus3f the

cycle of the MCA test, the 48 hour period will be lengthened.

5. Output of MCA monitored on an eight channel chart recorderwhen electronic tests are not performed.

The following points will be monitored:

1. Temp TLM

2. MO Pitch moment

3. M~ Roll moment

4. Mp Yaw moment

5. Power "On off" relay TLM

6. BO Pitch magnetic field

7. B~ Roll magnetic field

8. B4 Yaw magnetic field

Distribution: G. BranchflowerH'. NeumannD. MurrayE. ScopelW. RichmondMCA Dist., Ithaco

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I Report #90538File No. 10-272426 September 1972

R.Z. Fowler, W. Henniger, V. Selby, R. Shen,D. Sonnabend

4 A. C. Stickler

SUBJECT: RMP polarities

After looking up (with Bill Henniger's assistance) oncetoo many times the polarities of the RMP inputs and output,the author records here in black and white what he knows aboutthe RMP's on Nimbus and ERTS.

I. Input Axis, Orientation:.

, roll

/4-. RMP input axis

yawpitch

II. Equations:

A. In Aerodynamic Coordinates

= -~ sin 450 -0o cos 450 + ;cos 450 -0wosin 450 =RMP

=- _ 0/--I + )

W0 (1)

B. In Astrodynamic Coordinates

substituting - Pfor i

4RMP = Uo ( +4 + + - 4 )

W0here w = Orbital angular rate ( =10-3

here 0 = Orbital angular rate ( : 10

(2)

rad/sec)

'RMP = Output (without voltage scale factors) of RMP

C. In ERTS a signal = twice the roll error 4 andopposite in sense to the input for a positive yawerror p is added to the RMP's inputs. Then (1)becomes

TO:

FROM:

Report #90538File #10-2724Page 2

'RMP = - "0 ( _- f+ - p)

W0

If the yaw reaction wheel is doing its job properly

RMP = 0 and (3) becomes

( s + 1) = ( s + 1) f

and i follows (i.e., is equal to) p

D. When working in Astrodynamicadd +24 to (2), making (for

( s +wo

1 )* = -( S + !')s0

Coordinates, we shouldARMP - O )

and (5)

ACS:erk

cc: RZFW.HV.S.R.SD.S.File

(3)

(4) '

I

i.

I

QUALIFICATION TEST REPORT ·

OF

MAGNET CONTROL ASSEMBLY

S/N PR-1

Prepared by:R.R.Femin

R. R. FlemingR & QA Engineer

Prepared by: P2. kSaR. ShenProject EngineerMCA

I

Report No. 90548File No. 10-2724October 5,_A972Approva '/-r

QUALIFICATION TEST REPORT

of

MAGNET CONTROL ASSEMBLY

CONTRACT NUMBERNAS5-21867

PREPARED FOR:

Goddard SpaceFlight Center

Greenbelt, Maryland

PREPARED BY:

ITHACO INC.735 W. Clinton St.Ithaca, New York 14850

I

TABLE OF CONTENTS

1.0 Qualification Vibration Discussion

2.0 Vibration Testing

3.0 Vibration Results

4.0 Vibration Mounting Photographs

5.0 Vibration Test Plan

-3

K

Report #90548File #10-2724Page 1

1.0 QUALIFICATION VIBRATION

Purpose

This report summarizes the results of the Qualification levelvibration tests performed on the Magnet Control Assembly, PR1.The vibration levels were in accordance with GSFC Environ-mental Test Specification S-320-EN-1 dated November 1971.The vibration was performed according to the Vibration TestPlan, ITHACO Report No. 90522 Rev. A (attached) with func-tional testing and visual inspection as noted.

2.0 VIBRATION TESTING

The MCA was subjected to vibration at GSFC facilities onSeptember 26, 27, 1972. The units, MCA D41105G1 S/N15063and Triaxial Magnetometer probe C31512 S/N 15062 (SchonstedtSAM-63B-7 S/N4493) were attached to a universal vibrationfixture by measn of adapter plates, see photographs onPage 3. Mounting of each unit was by means of four #8-32socket head screws.

An increase in the level of mechanical noise of the MCA unitindicated an apparent resonance at about 700 Hertx in allthree axes. This is typical of other units undergoing similartesting.

After both sinusoidal and random vibration were completedin each axes, a functional test was performed. The testconsisted of the following:

Telemetry Outputs Measured

1. B field amplitude (3 axes)2. B field polarity (3 axes)3. Magnetic moment (3 axes)4. Power on/off status5. Acquisition on/off status6. Temperature

The functional test of the Magnetometer Probe consisted ofsteps 1 through 3. The units were also visually inspectedfor any change in torque striping on the assembly screwsand proper securing of the connectors and cables.

3.0 0 RESULTS

The MCA electronics and probe units have demonstrated the capa-bility to survive Qualification sinusoidal and random vibrationlevels. The functional testing indicated normal operation,

Report # 90548File #10-2724Page 2

3.0 Continued

of the units after each axis of vibration. Visual inspec-tion indicated no evidence of degradation. Post vibrationacceptance testing again verified normal operation of the MCA.

VIBRATION MOUNTING Report #90548 Page 3

MCA - X AXIS MCA - Y AXIS

MCA - Z AXIS

(THRUST)

MAGNETOMETER PROBE

Z AXIS (THRUST)

ITHACO, Inc. 735 W. Clinton Ithaco, New York 14850

Report #90522 Rev AFile #10-2724

October 4, 1972Page 1

Approval: J c_/

To: G. Branchflower, MCA

From: R. Shen

Subject: Vibration Test Plan

TABLE OF CONTENTS

1. Mounting Axes

2. Connectors Attached to MCA for support

3. Power

4. Pre vibration set up

5. Vibration level

6. Post vibration check

Report #90522 Rev AFile #10-2724

Page 2

MCA AND MAGNETOMETER VIBRATION TEST

1. Mounting Axes

(a) The Schonstedt Magnetometer vibration axesare shown below.

zTHRUST

X

I -I - y -

I .-1'

iI

i

1 ,

?v

0

t/

il.1iI

i:

I

I

IIs

II

I

I

i

iIIIII

Report #90522 Rev APage 3

(b) The MCA vibration axes are shown below.

z

THRUST

-v X

- - Y

Note the X and Y axes are 45° off fromroll and pitch axes.

the actual

/I/1

I

I -

Report #90522 Rev APage 4

2. Connectors attached to MCA during Vibration Test

(a) The only cable attached to the Magnetometer duringthe vibration test will be the pigtail. The cablewill be taped down one foot away from the magnetometer.

(b) The connectors with cables attached to the MCAduring vibration will be:

A2J1 (25 pin) directly from the Magnetometer

A3J3 (25 pin)

A3J3 ( 9 pin)

A4J1 (15 pin)

A4J2 (15 pin)

A4J3 (15 pin)

AlJ1 (15 pin)

Harness cable

All the connectors on the cables are femaletype and they will be taped down about onefoot away from the MCA during vibration.

3. Power

The -24V power will not be on during the Vibration Test.

4. Pre Vibration set up

Upon completion of final assembly per MOPS 30.37 andRQPS 15-31 pre vibration checks consisting of ATPS 1106will be performed. This will include isolation checks,six XY plots and command and TLM status.

5. Vibration test levels

The vibration levels are as specified by GSFC.

Report #90522 Rev A.Page 5

a) MagnetometersVibration levels according to S-320-EN1, Nov. 1971

SINUSOIDAL

Frequen Amplitude - "g" O-to-Peak

Range Thrust Transverse(cps) Axis Axes

5-100 15.0* 15.0*100-200 10.0 10.0200-2000 5.0 5.0

*Vibration limited to 1/2" double amplitude.Sweep Rate: 1 octave/minute.

RANDOM

PowerFrequencyerRange SpectralRange Density

Direction (cps) (Degsity g-RMS

ThrustAxis 20-2000 0.09 13.4

TransverseAxes 20-2000 0.09 13.4

The duration of the test shall be 4 minutes ineach direction -- 12 minutes total.

4

#90522 Rev A

b) MCAVibration levels according to S-320-EN1, Nov. 1971

SINUSOIDAL

Frequency Amplitude- "g" O-to-Peak

Range Thrust Transverse(cps) Axis Axes

5-40 8.0* 6.0*

40-200 10.0 18.0

200-2000 5.0 5.0

*Vibration limited to 1/2" double amplitude.Sweep Rate: 1 octave/minute.

RANDOM

PowerFrequency SpetralSpectral

RangeDesityDirection (cps) /cps) g

(9~/cps) g-RMS

ThrustAxis 20-2000 0.09 13.4

TransverseAxes 20-2000 0.09 13.4

The duration of the test shall be 4 minutes ineach direction -- 12 minutes total.

ReportPage 6

44.

I .

:I

, ; ;. i p7, . . .1

JI

Report No. 90522 Rev APage 7

6. Post Vibration Check

After the vibration of each axis, the assembly screwswill be checked to see if any of them have come loose.Voltages of all telemetry points will be recorded.

(a) Test

After the entire vibration test has been completed,the MCA will be retested per ATPS 1106.

R. Shen

Distribution: G. BranchflowerH. NeumannD. MurrayE. ScopelW. RichmondMCA Dist., ITHACO

Documents

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