Conquering the universe does not require the world’s most powerful microprocessor. The real secret is to make full use of the running characteristics of the component, even if it is a little outdated or even the performance is not optimal. Let’s take a look at how NASA’s unmanned Rover perseverance landed safely and reliably on Mars.
Man takes a step towards Mars
After millions of kilometers of flight, NASA’s perseverance rover finally landed on the surface of Mars on February 18, 2021. We can regard this event as a historic mission, because despite the long distance, harsh cosmic environment and weak hardware, human devices have successfully reached the red planet. It is worth noting that light travels the same distance in about 12 minutes on average. Therefore, it takes the same time to collect radio signals, images and information.
In order to accomplish this “impossible task”, NASA uses a processor installed in Apple IMAC G3 computer, which adopts the processor architecture of 1997 – the operation frequency is only 200MHz, and the RAM memory is 256MB. It is not even the fastest processor in the commercial processor family at the same level.
Why lower order technology?
There is a reason behind this choice. Aircraft designers are more concerned about the reliability and durability of airborne computers than just computing power. Simple smartphones usually perform faster. The mission to Mars requires that the CPU is always working. Radiation bombardment will seriously and easily damage the electronic components of modern processors. On the other hand, Apple’s third-generation CPU G3 will not be damaged by radiation, and can withstand strong radiation and temperature.
On earth, you can significantly increase the speed of the processor without worrying about any problems. The electrical, thermal, atmospheric and electromagnetic conditions are very comfortable and stable, because the earth’s atmosphere protects us with solid protective covers. However, the universe is very different. There is a huge power radiation between 100 MeV and 1 GeV, which may change the function of the circuit. The impact of a single ionized particle on the processor is enough to cause calculation errors or even serious damage.
Slow but safe and reliable
According to today’s standards, the chips used in the “perseverance” Rover are slow, but they can meet all the reliability test requirements. Even prolonged exposure to radiation will not impair its function. Yes, in the era of microprocessors with clock frequencies over 3 GHz, G3 processors with a speed of only 200 MHz are obviously difficult to survive. However, it may be more appropriate to say “a slow and steady victory”.
Even under severe conditions, high reliability is the most typical feature of a processor. This is a specially designed radiation resistant version that can operate at temperatures between -55 ° C and +125 ° C (-67 ° F and +257 ° f), especially considering the very cold environment on Mars. In addition, the module is also very light and thin, allowing various radiation penetration. The radiation resistant single board computer rad750 manufactured by BAE Systems can safely withstand these conditions.
The requirements of spacecraft are extremely critical. Saving a few millimeters of space or a few grams of weight is the most basic condition. The memory capacity is maintained at a very low level. 2 GB of flash memory, 256 MB of available RAM and 256 KB of EEPROM are sufficient. The processor “only” has 10.4 million transistors, 1000 times that of today’s smart phones. The perseverance rover is equipped with two brains, one of which starts immediately when the first processor fails.
Extremely safe and reliable processor.
The perseverance rover is also equipped with an inertial measurement system (IMU), which provides 3-axis information about its position to perform accurate vertical, horizontal and lateral movements. The sensor connected to the computer records many parameters, such as temperature, voltage, energy storage and power of the solar cell, to ensure that all operating conditions are stable. Using this data, you can control information exchange operations, snapshots, and various instructions useful for exploring new environments.
This is not the first time this type of processor has been used. Almost all of the more than 100 satellites around the earth use this rad100 computer, and so far there has been no problem. Today, the portable devices we use (notebook computers, smart phones, etc.) have strong computing power, while the highly critical space exploration can achieve “impossible tasks” with less resources.
Editor in charge: PJ