On December 20, 2017, the US National Aeronautics and Space Administration (NASA) decided on the further direction of its program called New Frontiers. Thomas Tsurbuchen, head of NASA's Science Directorate, spoke about the space agency's plans at a press conference. According to him, the next automatic space station within the framework of the New Frontiers program will go either to Titan (satellite of Saturn) or to the comet Churyumov-Gerasimenko. To which of these two space objects the automatic space station will go will become known only in 2019.
In the event that NASA specialists opt for a comet, the agency will send a spacecraft to it, which will have to take samples from its surface, and then send them to Earth. This finalist project is called CAESAR. The main goal of this mission is to collect organic compounds in order to understand how comets could contribute to the origin of life on our planet. It is worth noting that the Philae probe, delivered to its surface by the European station Rosetta, has already landed on the Churyumov-Gerasimenko comet. However, the probe managed to transmit only telemetry to Earth, after which the connection with the device was lost. At the end of September 2016, the Rosetta station was deorbited and sent to collide with a comet.
In the event that NASA's choice is made in favor of Titan, the Dragonfly spacecraft will be sent to its surface, which has already been called a nuclear helicopter, but outwardly it will more resemble a quadrocopter. Dragonfly will have to scan the surface of Titan in order to determine what exactly it is made of and how it is arranged. Also, the space helicopter will have to answer the question: what are the atmospheric conditions on this satellite of Saturn. Specialists from the American space agency believe that extraterrestrial life forms may exist on Titan.
Titanium in natural colors (photograph by Cassini)
The finalists of the competition for the best space mission project within the framework of the New Frontiers solar system exploration program were two development teams, a total of 12 candidates took part in the competition. Both projects sounded above will receive approximately $ 4 million a year to work out the details and concept. They must finalize their programs by July 2019, having studied all the possible risks of their missions, and then come up with a final proposal. The winner's project will be launched at the end of 2025. The development of each of the missions will require approximately $ 850 million, the winner's project will receive this amount from NASA, and the agency will also cover all the costs of launching the winning spacecraft into space - approximately another $ 150 million.
As experts note, the announced "price tag" is approximately twice the cost of "light" space missions within the framework of another program - Discovery, and also 2-4 times less than the budget of "flagship" robotic stations and NASA space telescopes. The announced budget allows a fairly large and extensive set of instruments to be placed on the probes, as well as long-lived radioisotope power supplies, but in terms of their capabilities and lifespan, these probes will still be inferior to such flagships as Cassini, Galileo and Voyagers.
It is worth noting that as part of the New Frontiers program, the US space agency has already completed three successful missions. So the Juno probe is studying the orbit of Jupiter, the New Horizons spacecraft is currently heading towards Pluto, and OSIRIS-REx is flying to the asteroid in order to take samples from its surface. According to Thomas Zurbuchen, the agency has not yet made a decision on which launch vehicles will be used to launch a particular mission. At the same time, he expressed confidence that by the time work begins on the creation of the required stations and probes, the SLS heavy rocket, as well as private space "heavy trucks" will be ready to launch a new generation of interplanetary American probes.
Nuclear Helicopter on Titan - DragonFly Mission
“Titan is a unique celestial body with a dense atmosphere, lakes and real seas of hydrocarbons, a cycle of substances and a difficult climate. We expect to continue the Cassini and Huygens case in order to understand whether there are all the "bricks of life" on the surface of Titan and whether life can exist on it. Unlike other landing modules, our "dragonfly" will be able to fly from place to place, moving hundreds of kilometers, "- told the head of the DragonFly mission Elizabeth Turtle.
Comparison of the sizes of the Earth, Titan (bottom left) and the Moon
Titan is the largest moon of Saturn and the second largest moon in the entire solar system (second only to Jupiter's moon Ganymede). Also, Titan is the only body in the solar system, with the exception of the Earth, for which the stable existence of liquid on its surface has been proven, and also the only satellite of the planet that has a dense atmosphere. All this makes Titan a very attractive object for various scientific research and study.
The diameter of this satellite of Saturn is 5152 kilometers, which is 50% larger than that of the Moon, while Titan is 80% larger than our planet's satellite in mass. Also, Titan is larger than the planet Mercury. The force of gravity on Titan is about one-seventh that of Earth's gravity. The satellite's surface is composed primarily of water ice and sedimentary organic matter. The pressure at the surface of Titan is approximately 1.5 times higher than the pressure at the earth's surface, the air temperature at the surface is -170.. -180 degrees Celsius. Despite the rather low temperature, this satellite is compared with the Earth in the early stages of its development. Therefore, scientists do not exclude that the existence of the simplest forms of life is possible on Titan, in particular, in the existing underground reservoirs, the conditions in which can be much more comfortable than on its surface.
The Dragonfly, the brainchild of scientists at Johns Hopkins University, will be a versatile lander equipped with multiple propellers that enable it to take off and land vertically. In the future, this will allow an unusual helicopter to explore the surface and atmosphere of Titan. “One of our main goals is to conduct research on methane rivers and lakes. We want to understand what is going on in their depths,”- said the chief leader of the Dragonfly mission, Elizabeth Turtle. “In general, our main task is to shed light on the mysterious environment of the satellite of Saturn, rich in organic and prebiotic chemistry. After all, Titan today is a kind of planetary laboratory, where it would be possible to study chemical reactions similar to those that could have caused the origin of life on Earth."
A project like this, if it wins the competition in 2019, will be very unusual and new even for NASA. Thanks to its two features, the Dragonfly device will be able to move from place to place. The first is the presence of a nuclear power plant, which will provide it with energy for a very long time. The second is a set of several powerful propeller motors that can lift a heavy exploration vehicle into Titan's dense air. All of this makes the Dragonfly somewhat similar to helicopters or quadcopters, with the only exception that the space nuclear helicopter will be designed to operate in much harsher conditions than on Earth.
Nuclear helicopter Dragonfly on the surface of Titan, NASA illustration
Experts note that this drone will be fully supplied with energy produced by a radioisotope thermoelectric generator (RTG). Titan's rather dense and thick atmosphere makes any technologies for converting solar energy into electrical energy ineffective, which is why nuclear energy will become the basic source of energy for the mission. A similar generator is installed on the Curiosity rover. During the night, such a generator will be able to fully charge the drone's batteries, which will help the aircraft to complete one or several flights during the day, with a total duration of up to one hour.
It is known that the Dragonfly toolkit is planned to include: gamma spectrometers that will be able to study the composition of Titan's subsurface layer (this device will help scientists find evidence of the presence of a liquid ocean under the satellite's surface); mass spectrometers for analyzing the isotopic composition of light elements (such as nitrogen, carbon, sulfur and others); geophysical and meteorological sensors that will measure atmospheric pressure, temperature, wind speed, seismic activity; he will also have cameras for taking pictures. The mobility of the "nuclear helicopter" will allow it to quickly collect various samples and perform the necessary measurements.
In just one hour of flight, this device will be able to cover a distance of 10 to 20 kilometers. That is, in just one flight, the DragonFly drone will be able to cover a greater distance than the American Curiosity rover managed to do during its 4 years of stay on the red planet. And during its entire two-year mission, the "nuclear helicopter" will be able to explore a rather impressive area of the surface of Saturn's moon. Thanks to the presence of a powerful power plant on board, the data from the device, according to Turtle, will be transmitted to Earth directly.
If the project wins the competition and receives final approval as part of the New Frontiers Solar System Exploration Program, the mission will launch in mid-2025. At the same time, DragonFly will arrive at Titan only in 2034, where, with a favorable development of events, it will work on its surface for several years.
On the way to the "Soviet" comet - the CAESAR mission
The second mission, which is currently claiming victory in the New Frontiers competition, may be the CAESAR probe - the first NASA spacecraft to take samples of volatiles and organics from the surface of a comet and then return back to Earth. “Comets can be called the most important, but at the same time the least studied objects of the solar system. Comets contain those substances from which the Earth was "molded", and they were also the main suppliers of organic matter for our planet. What makes comets different from other known bodies in the solar system? The interior of comets still contains volatiles that were present in the solar system at the time of its birth,”said Steve Squires, head of the CAESAR mission.
A snapshot of Comet Churyumov-Gerasimenko taken on September 19, 2014 with the Rosetta camera
According to the head of the NASA planetary department Jim Green, this mission will be sent to a very well-studied comet, in the vicinity of which another probe has already visited, we are talking about a European mission called Rosetta. The comet with the index 67P is called "Soviet", as it was discovered by Soviet astronomers. It is a short-period comet with an orbital period of approximately 6 years and 7 months. Comet Churyumov-Gerasimenko was discovered in the USSR on October 23, 1969. It was discovered by the Soviet astronomer Klim Churyumov in Kiev on photographic plates of another comet - 32P / Komas Sola, which were taken by Svetlana Gerasimenko in September of the same year at the Alma-Ata Observatory (the first picture in which the new comet was visible was taken on September 11, 1969)). Index 67P means that this is the 67th short-period open comet.
It was found that the Churyumov-Gerasimenko comet has a porous structure, 75-78% of its volume is void. On the illuminated side of the comet, temperatures range from -183 to -143 degrees Celsius. There is no constant magnetic field on the comet. According to the latest estimates, its mass is 10 billion tons (the measurement error is estimated at 10%), the rotation period is 12 hours 24 minutes. In 2014, using the Rosetta apparatus, scientists were able to find molecules of 16 organic compounds on the comet, four of which - acetone, propanal, methyl isocyanate and acetamide - had not previously been found on comets.
According to representatives of the American space agency, the choice of the CAESAR mission, which is sent to a well-studied comet, will allow to kill three birds with one stone - this makes the mission safer, cheaper, and also accelerates its launch. According to Squires, the installation of a capsule for the collection and return of soil from a comet to Earth will also play a role. This capsule was previously created by the Japanese space agency for the Hayabusa probe. “The choice of this capsule is explained by the fact that the CAESAR mission required a capsule that would continue to hold volatiles from the comet in a frozen form throughout the entire flight, up to touching the earth's surface. The capsule for the Hayabusa probe has a heat shield that prevents it from heating up to several hundred degrees Celsius, which could happen with the use of our technologies,”the American scientist noted.
Possible view of the CAESAR probe, illustration by NASA
According to NASA's plans, the CAESAR probe is planned to be equipped with an ion engine. It will reach the surface of the Churyumov-Gerasimenko comet relatively quickly. Samples of its matter, as Steve Squires hopes, could be on Earth in 2038.
