The Apollo Spacecraft - A Chronology.

Part 2 (H)

Recovery, Spacecraft Redefinition, and First Manned Apollo Flight

January 1968

1968

January 2

MSC called to the attention of North American Rockwell the number of discrepancies found at KSC that could have been found at Downey before hardware shipment. In an effort to reduce the discrepancies North American was requested to obtain and use the KSC receiving inspection criteria as a guide for shipping inspections. It was also suggested that the possibility of sending a few key inspectors to KSC for periods of three to six months to gain additional experience might be investigated.

Ltr., Kenneth S. Kleinknecht, MSC, to Dale D. Myers, North American Rockwell, Jan. 2, 1968.

January 5

ASPO Manager George M. Low discussed with Rocco Petrone of KSC the problem of high humidity levels within the spacecraft-lunar module adapter. Petrone advised that several changes had been made to alleviate the problem: air conditioning in the SLA and the instrument unit would remain on during propellant loading; and the rate of air flow into the SLA was increased. Also, technicians at the Cape had designed a tygon tube to be installed to bring dry air into the LM descent engine bell, should this added precaution prove necessary. With these changes, Low felt confident that the humidity problem had been resolved.

Memo for the Record, Low, "SLA humidity," Jan. 8, 1968.

January 5

Bellcomm engineers presented to NASA a proposed plan for lunar exploration during the period from the first lunar landing through the mid-1970s. The proposed program - based upon what the company termed "reasonable" assumptions concerning hardware capabilities, scientific objectives, launch rates, and relationships to other programs - was divided into four distinct phases:

  1. an Apollo phase using existing vehicles,
  2. a lunar exploration phase employing an extended LM with increased payload and longer staytime,
  3. a lunar orbital survey and exploration phase using remote sensors and photographic equipment on a polar orbit flight, and
  4. a lunar surface rendezvous and exploration phase using an unmanned LM to deposit the increased scientific equipment and expendables necessary to extend Apollo's manned lunar capability to two-week duration.
N. W. Hinners et al., Bellcomm Technical Memo 68-1012-1,"A Lunar Exploration Program," Jan. 5, 1968.

January 5

Apollo Special Task Team (ASTT) Director Eberhard F. M. Rees, Martin L. Raines, and Ralph Taeuber of MSC, and J. McNamara, North American Rockwell, visited Rocketdyne Division to review the status of the LM ascent engine backup program. The presentation was made by Steve Domokos.

The group was favorably impressed and felt that there was every indication that the Rocketdyne injectors would meet the LM requirements. ASTT recommended that MSC establish a board, chaired by the Chief of the Propulsion and Power Division and including one MSFC propulsion engineer, one MSFC manufacturing specialist, and other MSC personnel as required to provide a recommendation to ASPO of the ascent engine for LM-3.

Memo, Raines to Manager, ASPO, "Trip Report - Rocketdyne - January 5, 1968," Jan 8, 1968.

January 8

NASA Associate Administrator for Manned Space Flight George E. Mueller directed MSC Director Robert R. Gilruth to establish a task team to investigate why, in light of extreme precautions taken early in the program, the problem of stress corrosion in the LM was being encountered at such a late stage in Apollo. The problem, Mueller stressed, had been discovered at a most critical point in the program - the launch of the first LM was imminent and two subsequent vehicles were already well along in factory checkout. Any resultant slips in the LM program would seriously impact overall Apollo schedules. Gilruth replied he believed that such a team was not required. He affirmed that the reviews undertaken with the contractors in 1964 to guard against just these problems had proved inadequate when judged against present program demands. "The answer simply is that the job was not handled properly on the last go-round."

Ltrs., Mueller to Gilruth, Jan. 8, 1968; Gilruth to Mueller, Jan. 18, 1968.

January 9

George E. Mueller, NASA OMSF, in a letter to MSC Director Robert R. Gilruth, summarized a number of key Apollo program decisions required in order to emphasize the urgency of priority action in preparations necessary to certify the Apollo system design for manned flight. Mueller listed five items:

  1. Assuming a successful flight of Apollo 5, the LM design must be certified ready for manned flight on AS-503.
  2. A successful test firing of SM 102 at Cape Kennedy in January, in addition to the success of Apollo 4, would permit certification of the SM propulsion system for manned flight on AS-205.
  3. A successful launch vehicle test of AS-502 (Apollo 6) would require that the Saturn V design be certified ready for manned flight by early April 1968.
  4. A decision to certify the Block II CM design for manned flight should be essentially complete by early May 1968.
  5. Launch Complex 34 design should be certified for manned flight no later than early June 1968.
Ltr., Mueller to Gilruth, Jan. 9, 1968.

January 11

Apollo Data Coordination Chief Howard W. Tindall, Jr., summarized mission planning for the first two hours on the lunar surface. That period, he said, would be devoted to checking out spacecraft systems and preparing for launch (in effect simulating the final two hours before liftoff). This procedure embodied several important benefits. As a pre-ascent simulation, it would afford an early indication of any problems in the checkout routine. More importantly, the initial checkout procedure would prepare the LM for takeoff at the end of the CSM's first revolution should some emergency situation require such an immediate flight abort.

Memo, Tindall to distr., "First 2 hours on the moon is a countdown to launch - simulated or real thing," Jan. 11, 1968.

January 11

A Parachute Test Vehicle (PTV) test failed at El Centro, Calif. The PTV was released from a B-52 aircraft at 15,240 meters and the drogue chute programmer was actuated by a static line connected to the aircraft. One drogue chute appeared to fail upon deployment, followed by failure of the second drogue seven seconds later. Disreefing of these drogues normally occurred at 8 seconds after deployment with disconnect at deployment at plus 18 seconds. The main chute programmer deployed and was effective for only 14 out of the expected 40 seconds' duration. This action was followed by normal deployment of one main parachute, which failed, followed by the second main parachute as programmed after four-tenths of a second, which also failed. The main chute failure was observed from the ground and the emergency parachute system deployment was commanded but also failed because of high dynamic pressure, allowing the PTV to impact and be destroyed. Investigation was under way and MSC personnel were en route to El Centro and Northrop-Ventura to determine the cause and to effect a solution.

TWX, George M. Low, MSC, to NASA Hq., Attn: Apollo Program Director, Jan. 11, 1968.

January 11

CSM Manager Kenneth S. Kleinknecht wrote his counterpart at North American Rockwell, Dale D. Myers, to express concern about NR's seeming inability to implement configuration control of flight hardware and ground support equipment. Some progress had been made recently, Kleinknecht observed, but many steps still had to be taken to achieve effective configuration management on the CSM. The MSC chief pointed especially to North American's inability to ensure that final hardware matched that set forth in engineering documents, a weakness inherent in the separate functions of manufacturing: planning, fabrication, assembly and rework. MSC recommended a check procedure of comparing part numbers of installed equipment to the "as designed" parts list. "In short," Kleinknecht concluded, "I think that we should tolerate no further delay in establishing a simple 'as built' versus 'as designed' checking function, beginning with and including the first manned spacecraft."

North American began a more nearly complete engineering order accountability system, which provided an acceptable method of verifying the "as designed" to the "as built" configuration of each spacecraft. This system was planned to be applicable by the Flight Readiness Review on spacecraft 104 and on subsequent spacecraft at earlier points.

Ltrs., Kleinknecht to Myers, Jan. 11, 1968; Myers to Kleinknecht, Feb. 13, 1968.

January 13

The Senior Flammability Review Board met at MSC with Chairman Robert R. Gilruth, George M. Low, Maxime A. Faget, Aleck C. Bond, Charles A. Berry, Donald K. Slayton, Christopher C. Kraft, Jr., Kenneth S. Kleinknecht, all of MSC, and George Jeffs of North American Rockwell participating. The meeting summary reported that a 60-percent-oxygen and 40-percent-nitrogen atmosphere was acceptable from a crew physiological standpoint. The requirement for crew prebreathing before launch was not dependent upon launching with the atmosphere. Operationally, the crew could remove their helmets and gloves following orbital insertion and verification of the integrity of the cabin and its environmental control system; oxygen leakage would be allowed to enrich the crew compartment atmosphere.

On January 25, Berry, MSC Director of Medical Research and Operations, mote Gilruth: "We do not concur in the stated finding of the Board that a 60 per cent oxygen, 40 per cent nitrogen atmosphere is acceptable from a crew physiological standpoint. While it is true that a 60% oxygen, 40% nitrogen atmosphere at 5.6 psi [3.9 newtons per sq cm] should result in a cabin atmosphere physiologically equivalent to sea level conditions, this will not be the case in a spacecraft launched with a 60% oxygen, 40% nitrogen atmosphere to which no oxygen is added except by normal operation of the cabin regulator. Oxygen will be metabolized by the crew at a much greater rate than nitrogen will be leaking from the spacecraft. Assuming a case in which cabin relief valve seats at 6 psi [4.1 newtons per sq cm] and the cabin regulator does not begin adding oxygen until 4.8 psi [3.3 newtons per sq cm], the cabin atmosphere would then consist of approximately 49% oxygen. This is physiologically equivalent to a 12,000-foot [3,700-meter] altitude in air. It would then take approximately 50 hours at the nominal cabin leak rate for the cabin regulator to enrich the mixture to a sea level equivalent."

"Senior Flammability Review Board Meeting," MSC, Jan. 13, 1968; memo, Berry to Gilruth, "Senior Flammability Review Board Meeting, January 13, 1968," Jan. 25, 1968.

January 13

ASPO Manager George M. Low outlined for the NASA Apollo Program Director MSC plans to static-fire the service propulsion system (SPS) as a complete unit. Houston officials maintained that at least one firing of such a complete system was necessary to prove the adequacy of all SPS manufacturing, assembly, and testing. However, because of several potential adverse effects that might accrue to testing the first such available system (that for the 101 SM), MSC proposed to test-fire the 102 unit and interpret those results - including any possible damage to the SM structure itself - before making a final decision on whether to proceed with a ground firing of the actual flight hardware before flight.

Memo, Low to NASA Hq., Attn: Samuel C. Phillips, "Requirements for static firing of Apollo service propulsion subsystem," Jan. 13, 1968.

January 15

George E. Mueller, NASA Associate Administrator for Manned Space Flight, summarized for Administrator James E. Webb recent program progress in Apollo. Preparations were under way toward the revised January 22 launch date for Apollo 5. Delays had resulted primarily from difficulties with hypergolic loading and contamination problems, but propellant loading had been completed several days earlier. Target for the countdown demonstration test was January 19. At Buffalo, N.Y., the NASA stability team assisted Bell Aerospace Co. in tackling the LM ascent engine instability problem. Post-test analysis of the qualification engine had revealed gouging of the chamber wall near the injector face. Bell engineers were assessing the amount of requalification testing that would be required and continued their testing on reworked engines, seeking to find the cause of previous engine instabilities. Meanwhile, the backup injector program at Rocketdyne Division was proceeding extremely well. Tests employing fuel film cooling had produced increased engine performance within acceptable chamber erosion limits. Altitude tests were scheduled to follow within a few weeks.

Memo, Mueller to Administrator and Deputy Administrator, "Manned Space Flight Report - January 15, 1968."

January 17

Eberhard Rees, Director of the Apollo Special Task Team at North American Rockwell's Downey plant, wrote ASPO Manager George Low outlining what he termed "serious quality and reliability resources deficiencies" and proposed several steps to bolster NASA's manpower in these areas. Specifically, Rees cited the immediate need for additional manpower (primarily through General Electric) to make vendor surveys, test failure assessments, and specification review and analysis and establish minimum inspection points. In addition, Rees said, many areas were almost totally lacking in coverage by the government, such as monitoring qualification tests, receiving inspections, pre-installation test, and many manufacturing operations. He urged Low to reassess his requirements in Houston to determine how many persons MSC might contribute (along with those from MSFC and GE) to plug these vital areas.

Ltr., Rees to Low, Jan. 17, 1968.

January 17

Eberhard Rees, Apollo Special Task Team chief at North American Rockwell, participated in a failure review at Northrop-Ventura of the recent parachute test failure (see January 11) and in development of a revised test plan. Others at the review included Dale Myers and Norman Ryker from North American and W. Gasich and W. Steyer, General Manager and Apollo Program Manager at Northrop-Ventura. Those at the review put together a revised drop test program that resulted in only a two-week schedule delay because of the failure. Repair of the parachute test vehicle was under way. Meantime, tests would continue, employing bomb and boilerplate devices. Also, Rees decided to establish a Flight Readiness Review Board (headed by Joseph Kotanchik of MSC) to approve each drop test, and Northrop officials had established an internal review board to review test engineering and planning and were tightening their inspection and quality control areas.

Memo, Rees to Manager, ASPO, "Trip Report to Northrop-Ventura on January 17, 1968," Jan. 19, 1968; ltr., Kenneth S. Kleinknecht, MSC, to Myers, Jan. 19, 1968.

January 18

A meeting was held at MSC to determine necessary action concerning recent contamination of CM 103's potable water, oxygen, and water-glycol lines. North American Rockwell proposed that all 103 aluminum lines in the potable water and oxygen systems (approximately 72 segments) be replaced; and proposed to follow a chemical flushing procedure for the water-glycol lines to remove the aluminum oxide and copper contamination. North American estimated that these actions would cause a 15-17 day serial impact. Removal and replacement of all lines would result in an estimated impact of 45 days. A decision was made to concur with the North American recommendation and on January 19 Kenneth S. Kleinknecht, MSC, informed Dale D. Myers, North American, of the concurrence and authorized him to proceed immediately. In addition, Kleinknecht appointed a Special Task Team for Spacecraft 103 Contamination Control to ensure timely review of all contractor activities associated with removal of the contamination from the spacecraft environmental control system coolant system. Members of the team were: Wilbur H. Gray, Chairman; A. M. Worden, W. R. Downs, Jack Cohen, A. W. Joslyn, R. E. Smylie, R. P. Burt, and W. H. Taylor.

On February 20 Myers notified Kleinknecht of initiation of the potable water line changes and setting up of a monitor water-glycol system that would duplicate CSM 103 operations during the balance of checkout and would be examined for corrosion damage just before Flight Readiness Review.

Memo, Manager, CSM, ASPO, to Manager, ASPO, "Meeting held to determine course of action regarding contamination of CM 103 plumbing," Jan. 19, 1968; ltr., Kleinknecht to Myers, Jan. 19, 1968; memo, Manager, CSM, ASPO, to distr., "Spacecraft Plumbing Contamination Control Board," Jan. 19, 1968; ltr., Myers to Kleinknecht, Feb. 20, 1968.

January 18-19

Rolf Lanzkron and Owen Morris, Chiefs of MSC's CSM and LM Project Engineering Divisions, led a review of the 2TV-1 and LTA-8 (thermal vacuum test article and lunar module test article) thermal vacuum test programs at MSC. Chief concerns expressed during the review centered on the heavy concentration of testing during the summer of 1968, the need for simultaneous operation of test chambers A and B, and the lack of adequately trained chamber operations support personnel for dual testing. The review disclosed that maintenance of testing schedules for LTA-8 was most unlikely, even with a seven-day-a-week work schedule. (The central problem was the large number of open items that had to be cleared before start of the tests.)

Note, C. C. Gay, Jr., to LeRoy Day, Jan. 19, 1968.

January 19

Apollo Program Director Samuel C. Phillips wrote ASPO Manager George M. Low requesting that he establish and maintain a detailed comparison of configuration differences between the CSM and LM. This comparison, Phillips said, should include major interface differences, subsystems and components, weight, performance, and crew safety. Phillips ordered this comparison chiefly because the Apollo spacecraft was entering an extremely important phase to certify the vehicles for manned flight.

Ltr., Phillips to Low, Jan. 19, 1968.

January 22

NASA launched Apollo 5 - the first, unmanned LM flight - on a Saturn IB from KSC Launch Complex 37B at 5:48:08 p.m. EST. Mission objectives included verifying operation of the LM structure itself and its two primary propulsion systems, to evaluate LM staging, and to evaluate orbital performances of the S-IVB stage and instrument unit. Flight of the AS-204 launch vehicle went as planned, with nosecone (replacing the CSM) jettisoned and LM separating. Flight of LM-1 also went as planned up to the first descent propulsion engine firing. Because velocity increase did not build up as quickly as predicted, the LM guidance system shut the engine down after only four seconds of operation. Mission control personnel in Houston and supporting groups quickly analyzed the problem. They determined that the difficulty was one of guidance software only (and not a fault in hardware design) and pursued an alternate mission plan that ensured meeting the minimum requirements necessary to achieve the primary objectives of the mission. After mission completion at 2:45 a.m. EST January 23, LM stages were left in orbit to reenter the atmosphere later and disintegrate. Apollo program directors attributed success of the mission to careful preplanning of alternate ways to accomplish flight objectives in the face of unforeseen events.

Memo, Samuel C. Phillips to NASA Administrator, "Apollo 5 Mission (SA-204 LM-1) Post Launch Report #l," Feb. 12, 1968 (MOR M-932-68-05).

January 22

Joseph G. Gavin, Jr., LM Program Director at Grumman, advised ASPO Manager George M. Low of steps under way to attack the problem of stress corrosion in the LM. (Low had expressed MSC's concern over this potential danger on December 20, 1967.) While stating that he shared Low's concern, Gavin believed that stress corrosion would not prove to be of significance to the LM mission. However, his organization was prepared to reevaluate the LM's design and fabrication to determine to what extent the problem could be ameliorated. (Gavin denied that such metal corrosion could be absolutely eliminated using present materials as dictated by weight constraints on the LM design.) Gavin stated that he had created a special team of experienced designers and stress analysts to review engineering design of every LM part sensitive to stress corrosion, to review processes employed in fabrication of the LM structure, and to review the adequacy of the company's quality control procedures to ensure corrosion-free parts and assemblies.

Ltr., Gavin to Low, Jan. 22, 1968.

January 24

Eberhard F. M. Rees, head of the Apollo Special Task Team at North American Rockwell, met with Kenneth S. Kleinknecht, MSC, and Martin L. Raines, Manager of the White Sands Test Facility, to review the team's recent operations and the responses of North American and its numerous subcontractors to the team's recommendations. Kleinknecht listed what he thought were the chief problems facing the CSM program: the S-band highgain antenna (which he said should be turned over entirely to the task team for resolution); the parachute program; the environmental control system; and contamination inside the spacecraft. He urged that the team take the lead in developing solutions to these problems.

Memo for Record, Raines, "Review of Apollo Special Task Team Operations," Jan. 26, 1968.

January 25

In a letter to officials of the three manned space flight Centers, NASA Apollo Program Director Samuel C. Phillips called attention to the fact that as the time for the first manned Apollo flight was approaching constant concern for crew safety was becoming more pronounced. Phillips pointed out that the Crew Safety Panel, Flight Mechanics Panel, Launch Operations Panel, Hazardous Emergency Egress Working Group, and other Intercenter Coordination Panels had each dealt with specific aspects of Apollo crew safety. Individual Centers and contractors had exercised their crew safety responsibilities through system design, quality control, and test channels. Single-point failure analyses, dealing with specific hardware areas, had been made.

He said that these efforts had resulted in current provisions for rapid crew egress on the pad, for spacecraft abort during early phases of the launch, and for contingency flight modes. Phillips added, ". . . to insure that all of the many parts of the problem are properly integrated we should at this time step back and take another look at the overall crew safety picture from ingress to mission completion. The questions to be addressed are:

  1. Have we systematically analyzed all likely failure modes or anomalies which could jeopardize the crew from ingress to mission completion?
  2. In each of these cases do we have proper and timely cues coupled with a safe egress, abort, or contingency capability?
  3. Do we have a plan for the timely solution of the known crew safety related problems?
. . . I would like to have this essential area worked under leadership of MSC-focused at a high management level - with assistance as required from MSFC and KSC. . . ." In a reply to Phillips, on February 28, MSC's George Low indicated that John Hodge had agreed to undertake the task and had already held discussions on the subject with George Hage of Phillips' office.

Ltrs., Phillips to MSC, MSFC, and KSC, "Apollo Crew Safety Review," Jan. 25, 1968; Low to Phillips, Feb. 28, 1968.

January 26

The Special Task Team for CSM 103, appointed January 18, submitted a progress report of activities during daily sessions held January 22 through 25. North American Rockwell and NASA had reached agreements on:

  1. Cleaning and flushing of water management and oxygen systems. Since all aluminum lines except for three were replaced on CM 103 with new lines the resolution for cleaning and flushing these systems was quickly accomplished.
  2. Cleaning and flushing of water glycol system.
    1. Pressure integrity of the water glycol system would be confirmed by a hydrostatic check to 248 newtons per square centimeter (360 pounds per square inch). Leak integrity would be confirmed by subsequent checks with helium at 41 newtons per sq cm (60 psi).
    2. A resolution was obtained on the chemistry of the various cleaning and flushing fluids to be used on CM 103.
    3. Agreement was reached on verification of cleaning and flushing all flow paths.
The events leading to the situation on CSM 103 were reviewed in sufficient detail to make visible the errors in the discipline governing the flushing carts. RASPO Manager Wilbur H. Gray stated that it was the RASPO responsibility to ensure the upgrading and control of all such equipment which interfaced with the spacecraft. The team would convene again January 30 to review reports and continue with other activities required to ensure adequacy of the CSM 103 plumbing system.

Memo, Gray to distr., "Summary of progress on the Special Task Team for CSM 103 Contamination Control," Jan. 26, 1968.

January 26

A LM-2 flight and requirement meeting was held at MSC, attended by key MSC and NASA Hq. officials. The group reached three conclusions:

  1. The LM-1 performance on the January 22 Apollo 5 mission had been excellent for all conditions of the flight, as executed, with the exception of minor anomalies.
  2. The LM-2 flight objectives that were partially accomplished could be better accomplished by further ground testing or on subsequent manned missions. Further unmanned flight testing was not required for man-rating purposes.
  3. A LM-2 flight was not required to man-rate the ascent engine injector.
It was also agreed that a decision should be made not to fly the LM-2 mission, with this decision reversible if further evaluation of data from the LM-1 flight indicated any problems. This decision would be reviewed at the February 6 Manned Space Flight Management Council Meeting and on March 6 at the LM-3 Design Certification Review. The final decision would not be made until March 6.

Minutes of the LM-2 Flight Requirements Meeting, Jan. 26, 1968.

January 26

In response to a letter from ASPO Manager George M. Low in late December 1967, seeking assurances that no potential stress corrosion problems existed in the CSM, Dale D. Myers, CSM Program Manager at North American Rockwell, reviewed the three instances where problems had been encountered during the CSM project and iterated the extensive efforts to ensure against such potential problems. Echoing much the same words as his counterpart at Grumman, Myers stated that "it is not possible to guarantee that no single instance of stress corrosion will ever occur" and that circumstances "could create a problem not anticipated." He concluded that his company's efforts in this direction had been "entirely adequate and beyond the requirements of the contract and good practice in this industry," and he seated his belief that additional efforts in this area would not produce measurable results.

Ltr., Myers to Low, Jan. 26, 1968.

January 30

MSC CSM Manager Kenneth S. Kleinknecht, in a letter to North American Rockwell's Dale D. Myers, protested lack of North American reponse to written MSC direction concerning parachute test vehicles. Kleinknecht pointed out that MSC had "considerably modified our usual requirements in supporting the boilerplate 19 task being performed for you by Western Ways, Inc. These efforts seem to be completely negated by delayed go-ahead to Northrop Ventura for their portion of the task. I understand that neither Western Ways nor Northrop Ventura was given a go-ahead until January 19, 1968. The original written direction to NR [North American] was on November 9, 1967, to provide another parachute test vehicle (PTV) and give us an estimate of cost and schedule for another boilerplate PTV." If the effort on the PTV had started at that time, "we would now be able to use that vehicle rather than the bomb-type vehicles after losing PTV No. 2. The cost and schedule for boilerplate 19 was not submitted to MSC until later, on December 22, asking for a reply by January 2, 1968. Because of the holiday period, this written reply was furnished on January 5, after an investigation of the cost and schedule. The Engineering Change Proposal [ECP] stated a completion date of May 5; however, after a request by my people to see what could be done to improve this date, the improvement moved the Northrop Ventura schedule from June 14 to May 24 [a Friday]. This date is three weeks later than the date cited in the ECP and is completely unacceptable. . . ."

On February 29, Myers assured Kleinknecht that North American had proceeded with the BP-19A task in advance of NASA full coverage. Initial partial coverage was issued to North American on January 5, 1968. On March 14, in a letter of commendation, Kleinknecht thanked Myers for the attention given the BP-19A effort that made a March 15 completion by Western Ways possible. On May 27, W. H. Gray, RASPO Manager, wrote another letter of commendation thanking North American for completing BP-19A in time for a drop test in May 1968.

Ltrs., Kleinknecht to Myers, Jan. 30, 1968; Myers to Kleinknecht, Feb. 29, 1968; Kleinknecht to Myers, Mar. 14, 1968; Gray to Drucker, May 27, 1968.

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