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Ingenuity – Specs and technology of the Martian drone

by Fabio Affortunato
ingenuity-specifiche-dettagli
Reading time / Tempo lettura : 6 minutes / minuti


In previous posts related to the drone-UAS Inegnuity:

reference was made to the technology used by the engineers of the JPL (Jet Propulsion Laboratory) of NASA for Ingenuity, but dealing with drones it is a “must” to summarize in a post both the specs, the technology, the sensors, the payloads and the auxiliary systems for communication, energy and heating of this drone that is marking a new era in space exploration.

Ingenuity – Structure, specifications, technology, sensors, paylaods and auxiliary systems

Ingenuity – Structure and specs

Ingenuity, is a remotely piloted drone, identified by NASA as Mars helicopter, due to the position of its rotors, superimposed like those of a helicopter.

Structurally it is made up of four “legs” that are grafted onto a “box” that contains the paylaods, batteries and sensors. The counter-rotating coaxial rotors necessary for the thrust of about 1.2 m in diameter are engaged on the upper part of the box; on the top there are small solar panels that give energy to the drone and recharge the batteries.

ingenuity-drone-uas-marziano

Source: NASA

The technical specs, such as weight, rotor length, maximum flight height are summarized in the following table made public by NASA:

ingenuity-technical-specsIt should be noted that compared to a mass of 1.8 kg which on Earth corresponds to a weight of 1.81437 kg, on Mars Ingenuity has a weight of only 680 grams.

From what has been described it is evident that the most delicate part of ingenuity is the propulsion system. This image, taken from the interesting pdf ““Mars Helicopter Technology Demonstrator” in English, shows the detail of the rotors with some elements, such as the well-known “Servos” on land drones.

ingenuity-rotori-dettaglio

Source:  Mars Helicopter Technology Demonstrator pdf

Ingenuity – Technology and avionics

The heart of Ingenuity is a 500 Hz Qualcomm Snapdragon 801 processor with a Linux operating system, that is, it is a processor found on fairly dated mobile phones. The Snapdragon 801 has the task of controlling navigation, through the two paylaods (cameras) in the box and controlling the operation of the sensors.

The on-board avionics scheme consists of 5 circuits, and is well summarized in the following figure:

avionica-ingenuity

Source:  Mars Helicopter Technology Demonstrator pdf

Ingenuity – Sensors and payloads

The sensors used by Ingenuity are commercial products and include:

  • IMU – These are two Bosch 3-axis MEMS devices (Sensortec BMI-160), one for the upper sensor assembly in a vibration isolation holder and one on the lower sensor assembly where it is located together with the cameras
  • Inclinometer – This is a 2-axis MuRata MEMS device (SCA100T-D02)
  • Altimeter – This is a time-of-flight altimeter with a range of 10 meters from Garmin (Lidar-Lite-V3).

Due to the inconsistency of the red planet’s magnetic field, it is not possible during flight to use one of the well-known sensors on terrestrial drones: the compass, which Ingenuity is not equipped with.

As for the payload of Ingenuity it is made up of two high resolution cameras; one facing downwards and the other facing the horizon, both also useful for the purpose of controlling for navigation, landing and for scientific land surveying, as well as for image detection. Details below:

  • Navigation Camera (NAV) – With global shutter, grayscale aimed at 640 x 480 pixel nadir (Omnivision13, downloaded from NASA AMES RESEARCH CENTER on January 8, 2018 | http://arc.aiaa.org | DOI: 10.2514 / 6.2018-0023 OV7251) mounted on a Sunny Optics module. It has a 133 degree (horizontal) by 100 degree (vertical) field of view (FOV) with an average instantaneous field of view (IFOV) of 3.6mRad / pixel and is capable of capturing images at 10 frames / sec.
  • Return-to-Earth (RTE) Camera – This is a high resolution 4208 x 3120 pixel (Sony IMX214) Rolling Shutter sensor with an array of Bayer color filters coupled with an O-film optical module. This camera has a FOV of 47 degrees (horizontal) by 47 degrees (vertical) with an average IFOV of 0.26 mRad / pixel.

EBoth cameras are mounted on the drone’s lower sensor assembly as shown in the figure below. The NAV camera is pointed directly at the nadir and the RTE camera is pointed approximately 22 degrees below the horizon, resulting in an overlap region between the two camera image footprints approximately 30deg × 47deg. The overlay allows for the ability to record features between NAV and RTE images during post-flight data processing on Earth.

ingenuity-camera-dettaglio

Source:  Mars Helicopter Technology Demonstrator pdf

Ingenuity –  Communications

Ingenuity can communicate or be controlled from Earth only via radio link. This link is implemented using a standard 900 MHz COTS802.15.4 (with Zig-Bee protocol) chipset, SiFlex 02, originally manufactured by LS Research.

Two identical SiFlex parts are used, one of which is an integral part of a base station mounted on the host spacecraft, the other is included in the drone’s electronics.

These radios are mounted on identical custom PC cards that provide mechanical support, power, heat distribution and other necessary infrastructure. The boards on each side of the link are connected to their respective custom antennas The helicopter antenna is a loaded quarter-wave monopole positioned near the center of the solar panel (which doubles as a ground plane) at the top of the whole helicopter assembly and is powered through a miniature coaxial cable routed through the shaft to the electronics below.

One of the most critical aspects related to communications was’ use of standard assemblies for electronic systems to be used on Mars due to the low temperature on the surface of Mars. At night, the antenna and cable assemblies will see temperatures as low as – 140 ° C. The electronic components on both the base station and the helicopter will be kept “warm” (not below -15 ° C) by heaters. Another challenge is antenna placement and placement on the larger host spacecraft. Each radio emits approximately 0.75W of power at 900MHz with the card consuming up to 3W of power when transmitting and approximately 0.15W when receiving. The link is designed to transmit data at over-the-air speeds of 20 kbps or 250 kbps over distances up to 1000 mA. The one-way data transmission mode is used to retrieve data from the drone in real time during its flights.

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Source: NASA video YouTube

Ingenuity – Power and energy

The Ingenuity drone is powered by a lithium-ion battery system that is recharged daily by a solar panel. The energy in the battery is used to operate the heaters to survive the cold Martian nights, as well as to operate the drone actuators and avionics during short short flights.

The recharging of this battery through the solar panel takes from one to more Sol (Martian days). The battery consists of 6 Sony SE US1865 or VTC4 lithium-ion cells with a plate capacity of 2 Ah. The maximum discharge rate is greater than 25A, and the manufacturer’s specified maximum cell voltage is 4.25V.

The battery voltage is between 15-25.2V and the total mass of the 6 cells is 273g. A cell balance charge management system controlled by the FPGA ensures that all individual cells have a uniform voltage.

Energy consumption for night survival is estimated at 21 Wh.

The solar panel consists of metamorphic inverted cells (IMM4J) from SolAero Technologies. The cells are optimized for the solar spectrum of Mars and occupy a rectangular area with 680 cm2 of substrate (544 cm2 of active cell area) in a region centered and immediately above the coaxial rotor.

Ingenuity – Heating system and operation

Ingenuity must survive the cold of the night on Mars, where temperatures can drop to -100 °C or more. The most critical component is the battery which is kept above -15 °C all night while powering the Kapton film heaters attached to the battery cells.

The avionics cards in the ECM surround the battery and are also kept at a high temperature by virtue of their proximity to the hot battery pack.

The outermost fuselage thermal lining is made by Sheldahl with solar absorption α = 0.8 and infrared emissivity (IR) = 0.1 In addition to thermal losses across the gas (or airgel) gap, additional conduction losses occur in masts and through copper wiring that enters the ECM from the mast. To minimize the latter, cable gauges are selected to be thinner gauges that can still support current draw during operations without overheating.

Before flight, under the control of the FPGA, the thermal system powers the heaters in the engine control boards that have been exposed to ambient temperature. The internal temperature of the battery is brought up to 5 ° C to allow a high power extraction from the cells. During operation, the ECM and battery become warm due to avionics operations and battery self-heating. However, the thermal inertia of the elements is such that for short helicopter flights there is no overheating.


Credits about images: The cover image is taken from the NASA website. The images and video featured in the post, which are owned by NASA. The images and part of the content in the post are taken from the NASA pdf “Mars Helicopter Technology Demonstrator“. The use of the images is exclusively for the purpose of a better understanding of the contents of the article. Thanks to NASA for sharing these wonderful images.

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Last Updated on/Ultimo aggiornamento – 01/05/2021

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