Deal II and Explorers II and III

E

ven while the Deal I satellite (Explorer I) was being assembled, work was moving forward steadily on the Deal II payload. While Deal I used only the Geiger-Muller (GM) counter, high-voltage power supply, and scaling circuits from my Vanguard design, the Deal II package contained my complete University of Iowa instrument, including its onboard data recorder.

Building the Deal II instruments

Only days before leaving Iowa City for Pasadena in November, I had finished con­structing the engineering test model but had not had time to draw the final detailed schematic diagrams. They existed only in scattered notes in my notebook and in my mind.

When I drove from Iowa City to Pasadena, the trunk of our car carried those notebooks, the engineering prototype package, and the parts that I had already begun accumulating for the flight instruments. Figure 10.1 shows the prototype Vanguard package as it appeared at that time.

The overall configuration of the Jupiter C version had been worked out through our exchanges in late October and early November. Although the outward appearance of the complete Deal II satellite was markedly different from that of the Vanguard satel­lite (a long cylinder rather than a sphere, as shown in Figure 10.2), the internal canister housing the University of Iowa cosmic ray instrument was quite similar. Some idea of that resemblance is seen by comparing the Vanguard instrument package in Fig­ure 10.1 with what became the Explorer II instrument cylinder shown in Fig­ure 10.4. The primary differences were (1) substitution of a JPL-designed high-power

263

OPENING SPACE RESEARCH

FIGURE 10.1 Showing major portions of the hardware that was to become the Deal II satellite. Henry Richter (left) holds an early prototype of the low-power transmitter package, while the au­thor holds the prototype Vanguard instrument package developed at the University of Iowa. The formidable task was, in a very short time, to arrange those packages in a new form for launch on the Jupiter C launch vehicle. (Courtesy of NASA/Jet Propulsion Laboratory, California Institute of Technology.)

transmitter for the Naval Research Laboratory (NRL)-designed one, (2) changes to the NRL command receiver made necessary by the change to the two-transmitter (Minitrack plus Microlock) configuration, and (3) a change in electromechanical component locations necessitated by the higher spin rate.

Several tasks were especially pressing when I arrived at the Jet Propulsion Laboratory’s (JPL’s) gate. The first was to provide a catalog of needed parts. I completed a four-page list and turned it over to the JPL engineers on 4 December. They immediately placed a stack of rush procurement orders.

My second major task was to furnish workable schematic diagrams of my electron­ics design, which I drew by hand from the many sketches and notes in my laboratory notebooks. Most of those drawings were handed over to the JPL engineers by 16 December. However, I was still uneasy about a few of the tape recorder control circuit details. The engineers in JPL’s circuit development laboratory helped me with improv­ing those, and I eventually turned over the final schematic diagram on 9 January 1958.

Another urgent initial task was to arrange for the completion and installation of the onboard tape recorders. The tape recorder was unique—no comparable unit

CHAPTER 10 • DEAL II AND EXPLORERS II AND III

SUB CARRIER OSCILLATORS

AND

I KANSMITT ER ВАТТ ERIES

LOW POWER ANT GAP

AND TRANSMITTER

G M COUNTER

INSTRUMENTATION CYLINDER

COMMAND RECEIVER

PLAYBACK TRANSMITER

COSMIC RAY EXPERIMENT

ELECTRONICS

BATTERIES

>- TAPE RECORDER

HIGH POWER ANT GAP ■ROCKET CASING

FIGURE 10.2 The Deal II satellite. The six inch diameter instrumentation cylinder at the center of the figure contained the Iowa cosmic ray instrument.

was available from industry, and it would have taken too long for JPL to tool up to produce them. It was agreed that the instrument makers at Iowa, primarily Ed Freund, would complete the manufacture of four flight tape recorders. They would be shipped, however, with one task remaining undone. Ed had just completed the design of a new solenoid mounting bracket that converted the units from the Mark III to the Mark IV design, but had not yet machined enough for the flight units. We agreed that time would be saved if JPL machined the remaining mounts and installed the solenoids on them.

OPENING SPACE RESEARCH

On 26 November, I turned over the first completed recorder to Bob Garwood for him to begin making the modification. The second flight tape recorder arrived from Iowa on 5 December, and the others arrived at about one week intervals.

Also on 26 November, an engineer in Henry’s lab reported that he had been able to operate all of the Vanguard electronic circuitry in my prototype instrument package.

The JPL engineers had not been involved in designing the circuits in my cosmic ray package and had not had a hand in testing the components that I had selected. They established their own confidence in my work by building laboratory breadboard copies of many of the circuits and putting them through various tests. In only a few cases did they make minor changes.

We all shared a special concern about the performance of the onboard tape recorder in the more stressful environment of the Jupiter C launch vehicle. We were also anxious to verify the electronics packaging techniques that I had used. Although similar to those being used within the Vanguard project, some of the techniques were new to the JPL engineers.

Thus, we prepared a series of early vibration and spin tests using the Vanguard engineering design instrument package.[4] The JPL technicians mounted a new GM counter on my package to replace one that had been broken and installed a different turn-on plug on the top cover. We made the Mark IV modifications to the tape recorder and installed it in the package. Finally, we updated the wiring between the electronics decks.

They prepared a special mounting jig to attach the instrument package to the spin test facility. The initial results were encouraging. Everything, including playback initiated by the command transmitter and receiver, was normal up to a spin rate of 500 revolutions per minute (rpm). However, above that rate, recorder playback could not be reliably commanded. We were not sure whether the problem was in the tape recorder, in its control relays, or in interference to the radio frequency command signal caused by the noisy laboratory environment.

Milt Brockman suggested mounting a temporary test switch on top of the GM counter to bypass the command and control relays, in such a way that that switch could be actuated while the instrument was spinning. The engineers set up that ar­rangement overnight, and the next day, we made another spin test. The spin rate was increased to 1000 rpm, and operation was satisfactory. We then reconnected the playback relay, relocating it so that it was closer to the spin axis. During the next test, recorder playback was satisfactory up to 1100 rpm, but not at 1250 rpm. We concluded that the problem was with the relay, but we decided to proceed with it that way because the maximum spin rate during and after launch would be much lower at 750 rpm. The spin test series ended with a run with all of the sensitive

CHAPTER 10 • DEAL II AND EXPLORERS II AND III 267

components mounted in the positions envisioned for flight. That arrangement op­erated satisfactorily at 1190 rpm, but not at 1250 rpm. Again, we considered it acceptable.

A series of vibration tests of the cosmic ray package was uneventful. With the results of those vibration and spin tests in hand, I sketched the final internal physical arrangement for the Deal II cosmic ray instrument package on 9 December.2

Although the changes in the satellite program had substantially delayed my university course work, the objective of obtaining my M. S. degree was never far from my mind. Van Allen and I discussed that subject during several of our telephone discussions in early December, and he sent me a sample of a master’s thesis based on the development of another cosmic ray instrument. That helped me develop a feeling for the writing that I would have to do and provided additional motivation for very meticulous note taking.

A pivotal instrument review and planning meeting was called by payload manager Walt Victor for 11 December. Specific individuals were assigned responsibility for various portions of the work. The schedule called for the first flight unit to be shipped to Cape Canaveral on 10 February, with shipment of the second payload on 17 February. To make that schedule, the first State University of Iowa (SUI) cosmic ray package would have to be fully assembled and tested by 11 January, only one month hence, and the second unit would be required one week later.

That meeting served as the “starting gun” for the actual fabrication of the hardware. Following the meeting, Walt issued an “all hands” memo that began:

There is no pad in the Deal II schedule. All flight hardware must be completed on time and must operate satisfactorily in the environment [emphasis his]. It is suggested that all engineers consider the scheduled date as the absolute latest time the equipment can be made available, and that they make every effort to better the scheduled date whenever possible. I will be following the work progress very closely and expect to be notified immediately of any circumstances which would prevent making the schedule.3 I

OPENING SPACE RESEARCH

During much of January 1958, aside from my work on the GM counter calibrations, as recounted earlier, much of my effort went toward finishing and testing several of the Deal II circuits. In mid-January, a few design details on the tape recorder playback amplifier and relay control circuits were still being improved. One of those improvements was to add a protective circuit to unlatch the control relays in case the recorder should freeze, so that the batteries would not be drained if that should occur. My summary report to Van Allen on 20 January read:

Needless to say, all circuits which were not completely checked out when I left Iowa have now been. The recorder drive circuit [had not been], but has been found by now to operate from —25°C to +65° The playback amplifier required some rework, and now utilizes considerable negative feedback to stabilize its operating conditions. Its characteristics change very little from —25°C to +75°C. It delivers a saturated rectangular pulse to the modulator.4

That letter included a set of drawings for both the Deal I and II instrument packages, a five-page listing of all of the components being used in the flight payloads, and their selection criteria. I promised to send mechanical drawings in the near future.

I also reported:

My schedule is finalized now—will leave here the 26th, leave there [Cape Canaveral, not mentioned because of security] the 31st, arrive Iowa City the 31st at 2:05 PM, and leave Iowa City the 3rd at 2:15 PM. Had the thought that you might not be back in Iowa City by the 31st.

If not, will you send a wire? Also need the address at which I can contact you in Washington and your itinerary if possible.5

As mentioned earlier, I delayed my departure to Cape Canaveral for the Deal I launch until 28 January to make additional tests of the GM counter calibration setup and procedures. Even after those tests, I still had some reservations about the final calibrations. Beginning on 14 February, after I had returned from the Explorer I launch and my stop in Iowa City, I made a detailed assessment of the entire calibration setup, procedures, and results. After four days of work, I finally convinced myself that the calibrations were valid.6 I would have preferred to give the counters on the Deal II flight units a final run, but by that time, the first unit was already at the Cape. Any lingering concerns were not sufficient to warrant interfering with the remaining launch preparations.

By the end of Tuesday, 18 February, my work on Deal II appeared to be essentially complete, and it looked like I would be able to spend a few days at home with Rosalie and the two girls. My journal reported:

Payload I is built. It was recently pared down to remove weight, but is rebuilt. # II [the second payload for Deal II] is being built. There were three difficulties so far. (1) An internal short in receiver deck B2 caused a 150 ma. [milliampere] drain. Cleared OK. (2) Tuning fork deck D2 became intermittent. Replaced with D3. (3) This afternoon before leaving found out the playback head in recorder J2 was not delivering sufficient pulse amplitude. This will require disassembly & checking.7

CHAPTER 10 • DEAL II AND EXPLORERS II AND III 269

That marked the end of the payload development and assembly. During a long phone conversation with Van Allen on that day, we discussed many topics, including plans for preliminary analysis of the Explorer I data and for the upcoming Deal II satellite.

At the Cape, the JPL engineers were making several rather substantial last-minute modifications to the first Deal II flight payload mechanical structure. That included the substitution of a shorter shell, a lighter magnesium instrument container, and a lighter fretwork support for the low-power transmitter assembly. There was still considerable concern about achieving a sufficiently high orbit with a payload that was somewhat heavier than Explorer I, and every step imaginable was taken to reduce its weight. The other two Deal II flight payloads were modified in similar fashion at JPL before they were shipped to the Cape.

My brief respite was short-lived. On the 19th, two developments put me back into the crisis mode. The first was a failure during the environmental testing of the spare flight payload (the third Deal II payload). The recording amplifier quit operating, and the instrument would not respond to interrogations during the vacuum chamber test. After I analyzed the problem the next morning, the JPL engineers set about to repair it.

I turned my attention to the second crisis, the lack of readiness of the ground stations that would be needed to interrogate the satellite’s tape recorder. That problem is discussed in the next chapter.