One big or many small?



    Have you ever worried about the fate of the interplanetary probe? A large apparatus, in which years of labor were invested, stuffed with advanced scientific instruments, enters the atmosphere of a distant planet, and it is not a fact that it will respond from the surface. There are enough precedents - the probes were broken, destroyed in the atmosphere or fell silent for an unknown reason. And the whole mission was wasted. Even if the landing was successful, only one device could not be in several places at the same time, and had to choose between many potentially interesting places. The place also had to be safe - the risk of losing the probe outweighed the scientific interest. But now dozens of micro- and nanosatellites fly in the Earth’s orbit, what if this idea is applied to interplanetary stations?

    First success


    The first mission, where several small ones flew along with a large probe, was Pioneer-Venus-2 , launched in 1978. A large apparatus landed near the equator, and three small ones diverged to the sides. One sat down at ~ 60 ° north latitude, the second - far on the night side, and the third - on the daytime. The apparatus design was simple:


    1 - antenna, 2 - thermometer, 3 - thermal protection, 4 - sealed container with batteries and electronics, 5 - nephelometer , 6 - radiometer.

    Small devices did not even have a parachute. The “daytime” device exceeded the expectations of the designers, withstood the blow to the surface and transferred data for another hour.

    Strip of failure


    The next station, which bore the "clip" of vehicles, was the super-ambitious "Mars-96 . " The heaviest Martian station, in addition to the orbital module, carried two landing stations and two penetrators:



    landing stations in an inflatable cushioning shell had to parachute, and penetrators had to stabilize with an inflatable conical braking device and stick into Mars at a speed of ~ 80 m / s. After the impact, the front part was supposed to sink 5-6 meters, unwinding the wires behind it, and transmit data to the tail part remaining on the surface.



    Each penetrator carried 10 scientific instruments and promised to collect unique data about Mars. Until now, not a single device has plunged into Mars so deeply. It is unfortunate that the station did not leave Mars from Earth orbit and burned out in the atmosphere a few hours later.

    In the 90s, NASA launched the New Millennium program , in which two small probes, Deep Space 2, went to Mars with the Mars Polar Lander . They were housed in a heat-protective aerial envelope: Separated shortly before landing, they had to fall without a parachute, break the shell upon impact and plunge the front half a meter into Mars:









    On December 3, 1999, the devices plunged into the atmosphere of Mars, but neither the large Mars Polar Lander, nor the small penetrators got into contact. The cause of the accident of all devices remained unknown.

    Branch


    In the zero years, articles were written about the idea of ​​small spacecraft, but real interplanetary stations carried a maximum of one spacecraft for their descent to Jupiter , Mars, or Titan . But the concept of a simple device that is able to withstand entry into the atmosphere has received a curious branch. They suggested recording information about the passage of dense atmospheric layers in the “black box”, which would survive the destruction of the main apparatus and be able to transmit data for further investigation. So the Reentry Breakup Recorder (REBR) project was born , which already three times recorded destruction in the dense layers of the atmosphere of the ISS supply cargo ships and successfully transmitted data.


    The scheme of the apparatus. Nothing complicated - batteries, a data capture device and a transmitter.

    Based on REBR technologies, the Pico Re-Entry Probe project, a very cheap universal device that can withstand braking in dense atmospheres and transmit data, was proposed. For example, it is proposed to put a passing load on the satellites: The


    orbit of the carrier satellite gradually degrades, it burns out in the atmosphere, and PREP transmits data directly to the communication satellite, without the need for search and selection.

    Using PREP, it is proposed to obtain data on the behavior of subsystems and materials of spacecraft, or for example, conduct cheap atmospheric research.

    New Hope


    In recent years, the number of ideas for using micro-, nano- and picosondes has increased dramatically. Last summer, they wrote about the “chipsets” microcircuit probes, which are proposed to be dropped onto the Jupiter’s satellite Europe.
    This spring, the University of Toronto proposed to dump a swarm of devices into the atmosphere of Jupiter (SMARA project):



    And in March, the non-profit organization Planetary Science Institute proposed the MARSDROP project :



    It is proposed to place a landing probe with a controlled parachute-wing in a mastered aerial shell. Such a combination is expected to be able to provide an exact landing in an area of ​​Mars interesting from the point of view of science - a fresh crater, canyon, volcanic activity region, glacier. The developers suggest that such a probe will be able to fly up to 10 km in the atmosphere of Mars, compensating for the inevitable inaccuracy of braking in the atmosphere, and deliver a vehicle weighing 1 kg exactly to the target. It is expected that two MARSDROP vehicles, taken by passing cargo to the main mission, will increase its cost by no more than 5%.

    Analysis


    The idea of ​​using a swarm of probes for planetary exploration has the following advantages and disadvantages:

    Advantages:
    • A new level of scientific data collection. The grid of devices is able to give a spatial representation of climate, weather or geological data. One device cannot fundamentally do this.
    • Greater integral reliability of missions - failure of one device is not fatal.
    • The opportunity to take a greater risk - you can drop several devices in the Mariner Valley, on Olympus or on the plain of Hellas.
    • More scientific evidence. A random miss during the landing of the Chinese lunar rover revealed new information about the geology of the moon. And if a hundred vehicles landed?


    Disadvantages:
    • The mass limitation of one apparatus means that it is impossible to put complex and large scientific instruments on it. Also, devices are unlikely to be able to move or exist for years.
    • Small sizes dictate small energy - an orbital repeater becomes mandatory. Also, the requirements for data transmission are increasing for the repeater.


    In my opinion, the advantages obviously outweigh, I hope, in the near future, swarms of probes will complement the large complex devices that we are familiar with.

    List of sources used


    In addition to the sources indicated in the text, the following were used:

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