Launch of Mariner 1
|Mission type||Venus flyby|
|Operator||NASA / JPL|
|Mission duration||294.5 seconds|
Failed to orbit
based on Ranger Block I
|Manufacturer||Jet Propulsion Laboratory|
|Launch mass||202.8 kilograms (447 lb)|
|Power||220 watts (at Venus encounter)|
|Start of mission|
|Launch date||July 22, 1962, 09:21:23GMT|
|Rocket||Atlas LV-3 Agena-B|
|Launch site||Cape Canaveral, LC-12|
Mariner 1 was the first spacecraft of the American Mariner program, designed for a planetary flyby of Venus. It cost US$18.5 million in 1962. It was launched aboard an Atlas-Agena rocket on July 22, 1962. Shortly after takeoff the rocket responded improperly to commands from the guidance systems on the ground, setting the stage for an apparent software-related guidance system failure. With the craft effectively uncontrolled, a range safety officer ordered its destructive abort 294.5 seconds after launch.
According to NASA's current account for the public:
The role of a software error in the launch failure remains somewhat mysterious in nature, shrouded in the ambiguities and conflicts among (and in some accounts, even within) the various accounts, official and otherwise. The probe's mission was accomplished by Mariner 2, which launched 5 weeks later.
The Mariner 1 spacecraft was identical to Mariner 2, launched on 27 August 1962. Mariner 1 consisted of a hexagonal base, 1.04 meters (3.4 ft) across and 0.36 m (1.2 ft) thick, which contained six magnesium chassis housing the electronics for the science experiments, communications, data encoding, computing, timing, attitude control and the power control, battery and battery charger, as well as the attitude-control gas bottles and the rocket engine. On top of the base was a tall pyramid-shaped mast, on which the science experiments were mounted, which brought the total height of the spacecraft to 3.66 m (12.0 ft). Attached to either side of the base were rectangular solar panel wings with a total span of 5.05 meters and width of 0.76 meters (16.6 × 2.5 ft). Attached by an arm to one side of the base and extending below the spacecraft was a large directional dish antenna.
The Mariner 1 power system consisted of the two solar-cell wings, one 183 × 76 cm (72 × 30 in), and the other 152 × 76 cm (60 × 30 in), with a 31 cm (12 in) dacron extension (a solar sail) to balance the solar pressure on the panels. Those panels powered the craft directly or recharged a 1000-watt-hour sealed silver–zinc cell battery, which was to be used before the panels were deployed, when the panels were not illuminated by the Sun, and when loads were heavy. A power-switching and booster regulator device controlled the power flow. Communications consisted of a 3-watt transmitter capable of continuous telemetry operation, the large high-gain directional dish antenna, a cylindrical omnidirectional antenna at the top of the instrument mast, and two command antennas, one on the end of either solar panel, which received instructions for midcourse maneuvers and other functions.
Propulsion for midcourse maneuvers was supplied by a monopropellant (anhydrous hydrazine) 225 N retro-rocket. The hydrazine was ignited using nitrogen tetroxide and aluminium oxide pellets, and thrust direction was controlled by four jet vanes situated below the thrust chamber. Attitude control with a 1° pointing error was maintained by a system of nitrogen gas jets. The Sun and Earth were used as references for attitude stabilization. Overall timing and control were performed by a digital Central Computer and Sequencer. Thermal control was achieved through the use of passive reflecting and absorbing surfaces, thermal shields, and movable louvers.
The scientific experiments were mounted on the instrument mast and base. A magnetometer was attached to the top of the mast below the omnidirectional antenna. Particle detectors were mounted halfway up the mast, along with the cosmic-ray detector. A cosmic-dust detector and solar plasma spectrometer/detector were attached to the top edges of the spacecraft base. A microwave radiometer, an infrared radiometer and the radiometer reference horns were rigidly mounted to a 48 cm (18.9 in) diameter parabolic radiometer antenna mounted near the bottom of the mast.
In addition, a small 91 × 150 cm (3 × 5 ft) United States flag was folded and stowed onboard Mariner 1 (and Mariner 2), before it was mated to the Agena.
The launch was aborted due to a combination of two failures: a malfunction of the GE Mod III-B guidance system rate beacon and a faulty guidance program. The rate-beacon malfunction occurred at T+93 seconds, when the booster phase was still in progress, and so did not produce an immediate effect (see below).
The rate beacon on the rocket sends speed data to the ground-based guidance computer. The computer uses this and positional information to compute course corrections, which are sent back to the rocket.
However, "the guidance antenna on the Atlas performed poorly, below specifications. When the signal received by the rocket became weak and noisy, the rocket lost its lock on the ground guidance signal that supplied steering commands".
Atlas-Agena vehicles utilized two different guidance system variants for Cape Canaveral and Vandenberg launches. Both of them proved to be troublesome and caused several in-flight malfunctions, leading to a redesign of the guidance system by General Electric in 1963.
The guidance system had an onboard program that could be activated in the event that the ground signal was lost, but it contained a faulty equation. Atlas vehicles flew on autopilot only during the booster phase, and the guidance system would activate following BECO (booster-engine cut-off) to steer the sustainer engine and perform adjustments to the flight trajectory. Due to the faulty guidance-system programming, largely unplanned yaw maneuvers occurred shortly after the start of the sustainer phase. The destruct command was issued by the range safety officer at T+294.5 seconds into launch. The Agena stage had no range-safety destruct system of its own due to weight restrictions, only an inadvertent separation destruct system (ISDS), which was wired to the Atlas adapter section and disabled at staging. If the Agena separated from the stack prior to Atlas SECO, the ISDS charges would activate and destroy it. Activation of the range safety system on the Atlas would also destroy the Agena. Had range safety action not been taken with Mariner 1's launch vehicle, the Agena and spent Atlas sustainer section could have come down in a populated area, so it was necessary to make sure that they were broken up.
There are several accounts of what happened.
The most detailed and consistent account was that the error was in the hand transcription of a mathematical symbol in the program specification for the guidance system, in particular, a missing overbar.
The error had occurred when a symbol was being transcribed by hand in the specification for the guidance program. The writer missed the superscript bar (or overline) in
by which was meant "the n-th smoothed value of the time derivative of a radius R". Since the smoothing function indicated by the bar was left out of the specification for the program, the implementation treated normal minor variations of velocity as if they were serious, causing spurious corrections that sent the rocket off course. It was then destroyed by the range safety officer.
The cryptic nature of the problems that led to the decision to abort Mariner 1, as well as the confusion in various reports on the incident, led to other explanations in the popular press.
Many accounts note a missing "hyphen" ('-') rather than the overbar, in either the equations, the computer instructions or the data. For example, Arthur C. Clarke wrote several years later that Mariner 1 was "wrecked by the most expensive hyphen in history".
The narrow window (45 days) before the launch of Mariner 2 left little time for inquiries, investigations, or recriminations. The official accounts (which included mentions of a missing hyphen) were the results of an inquiry conducted in less than a week.
Regardless of whatever may have given rise to initial reports of a "missing hyphen", the simplest and most consistent-sounding explanation that the public and Congress would accept would probably have been preferable to those who simply wanted to get on with the job of a Venus fly-by mission. The stories had contradictions, perhaps, but they were so technical that nobody who could have interfered with Mariner-program progress was likely to care about them or even notice. (After all, even in one later NASA account, the supposed "hyphen" is reported as missing from instructions at one point in the text, and from equations at another).
The New York Times, reporting on the results of a review board, said that the error stemmed from "the omission of a hyphen in some mathematical data". The same report also said the hyphen was "a symbol that should have been fed into a computer, along with a mass of other coded mathematical instructions".
This sort of inconsistency or ambiguity was seen in many subsequent variations on the story, official and otherwise. "Missing hyphen" versions of the story gained official support before the month was out. NASA official Richard B. Morrison testified before Congress that the supposed hyphen "gives a cue for the spacecraft to ignore the data the computer feeds it until radar contact is once again restored. When that hyphen is left out, false information is fed into the spacecraft control systems. In this case, the computer fed the rocket in hard left, nose down and the vehicle obeyed and crashed." (Note that Morrison says the spacecraft "crashed", not that it was intentionally destroyed).
In a NASA account submitted to Congress in 1963, the hyphen is described as missing in two different ways:
In the same 1963 report to Congress, Morrison's testimony from the previous year is recounted differently:
JPL's Mariner Venus Final Project Report in 1965 noted that, at 4 minutes and 25 seconds into the flight, there was an "unscheduled yaw-lift maneuver":
In a NASA report published in 1985, Oran Nicks offered another slightly differing account, but with the software-related error still identified as a missing "hyphen":
NASA's website now says the problem was:
In other accounts, the bug consisted of: