A Close Look at Project Lyra (A Closer Look at the Project Lira)

Good time of the day, Giktayms!

Yesterday I published an article “ Catch Up ʻOumuamua! The Lyra Project ”, and when I began to read the “Project Lyra: Sending a Spacecraft to 1I / 'Oumuamua (former A / 2017 U1)” report I mentioned in it, the Interstellar Asteroid, quickly It turned out that it would be necessary to translate it for a better understanding. I started with the most delicious third section “3. Concepts and Technologies ”, and while translating it, I wrote Denis Nyrkov, voyager-1 , that he had just translated the beginning of the article. So, the three of us, by joint efforts, we overcame the task. The third participant is Google’s translator. Honestly, without his participation, I simply would not bother with this article.

Links to previous articles about ʻOumuamua respected member with the nickname akurilov :

1) Date with ʻOumuamua. For the first time the interstellar object in the Solar System is open.
2) The first open interstellar object turned out to be unusual.
3) My review article about “Project Lyra” - Overtake ʻOumuamua! Project "Lyra"

Notes in italics in parentheses are mine. The list of sources is deliberately left as is, notes are added. So it will be easier to find sources. In the future, I plan to make several translations with names like: “A Close Look at Project Lyra # 00 (A Closer Look at the Project Lira No. 00)”, where instead of zeros there will be the source number from the list, if someone wants to join - you are welcome. In addition, everything is as in life, it is empty, it is thick. I want to make a new publication about the "Moon Village", the benefit is actual news and interesting information. That's all the preface.

Project Lira: sending apparatus to the interstellar asteroid ʻOumuamua (formerly A / 2017 U1)

Andreas M. Hein (1), Nikolaos Perakis (1), Kelvin F. Long (1), Adam Crowl (1), Marshall Eubanks (2), Robert G. Kennedy III (1), Richard Osborne (1)

1) Initiative for Interstellar Studies , Bone Mill, New Street, Charfield, GL12 8ES, United Kingdom
2) Asteroid Initiatives LLC


The first confirmed interstellar object discovered in our solar system, ʻOumuamua (formerly known as A / 2017 U1), gave us the opportunity to directly study material from another star system. Is it possible to intercept this object? The call to reach the object in reasonable time is difficult due to its large excess hyperbolic speed (speed minus the third cosmic speed ) of about 26 km / s, much faster than any device launched at the moment. This article provides a high-level analysis of the possible implementation of a similar mission in the near future. The launch of the device with an acceptable time for preparing the mission for 5–10 years requires an excessive hyperbolic velocity between 33 and 76 km / s for a mission between 30 and 5 years, respectively. Different mission durations and their speeds require estimates, taking into account the launch date, imply the output to the trajectory of interception by one impulse. Several technical possibilities are set out, including the Oberth maneuver ( or gravity maneuver ) near the Sun with chemical engines, and a more advanced possibility using solar or laser sails. To maximize the scientific result of the mission, it is highly desirable to slow down the apparatus at ʻOumuamua, due to the low scientific output during high-speed flight. It is concluded that, although the achievement of the object is a technical challenge, its implementation seems to be viable with technologies that are already in place or those that will appear in the near future.

1. Introduction

On October 19, 2017, an object near the Earth was discovered at the University of Hawaii using the Pan-STARRS telescope network data, originally called A / 0217 U1, but later renamed ʻOumuamua. It was discovered that this object having a speed in infinity (relative to the Sun) of the order of 26 km / s is not tied to the Solar System, and came to us from a point close to the solar apex (above the plane in which the planets move) from the Lyra constellation. Due to the fact that he did not have a tail when approaching the Sun, the object did not look like a comet and was recognized as an asteroid. Later observations from the Palomar Observatory indicated that the object had a reddish tint, similar to the color of objects from the Kuiper belt [3]. It looked like a sign of cosmic erosion. Its orbital properties were analyzed in [2,4].

At the moment, the frequency of hitting such objects in the solar system is poorly understood. Since ʻOumuamua is the closest macroscopic sample of interstellar material ( we are talking about so-called galactic rays ) probably with a distinctive isotopic imprint from all objects of the Solar system, the scientific result from obtaining samples of such an object is difficult to assess. A detailed study of interstellar material at interstellar distances is likely to take place no earlier than in decades, even if the Breakthrough Starshot project (for example) develops energetically. Consequently, a very interesting question is the possibility of using such a unique possibility of sending a spacecraft to ʻOumuamua to study it closely.

The Initiative for Interstellar Studies (a non-profit organization founded in England in 2012 ) or i4is for short, announced on 30 October a Lear project to answer these questions. The aim of the project is to assess the possibility of a mission to ʻOumuamua using current and expected technologies in the near future, and to offer a concept of a mission to accomplish a flying mission or a meeting with this asteroid. The challenge is complex: according to current estimates, Oumuamua has an excessive hyperbolic speed of 26 km / s. This is significantly more than any object launched by man into space at the moment. Voyager 1 - the fastest object ever created by man, has an excess speed of 16.6 km / s. Since ʻOumuamua already leaves the solar system, any device launched in the future will have to catch up with this asteroid. However, besides the scientific interest in obtaining data about this object, the very task of achieving it can advance modern space technologies. Consequently, the Lear project is not only interesting from a scientific point of view on this issue, but also from the point of view of technological challenges. Figure 1 displays the logo for the Lear project:

This article presents some results of a preliminary analysis of the various concepts of the mission to ʻOumuamua.

2. Analysis of trajectories

Given the hyperbolic excess speed and its inclination relative to the ecliptic of the solar system, the first question to answer is the required speed increment (DeltaV) to reach the object, a key parameter for designing a propulsion system. Obviously, a slower spacecraft will reach the object later than a faster spacecraft, which will lead to a compromise between the duration of the trip and the required DeltaV. In addition, the earlier the spacecraft is launched, the shorter the trip duration, as the distance of the object increases with time. However, the launch date over the next 5 years is likely to be unrealistic, and even 10 years can be difficult if new technologies are needed. Therefore, the third basic tradeoff is between the launch date and the off time / characteristic energy C3. The characteristic energy is the square of hyperbolic excess speed, which can be understood as the speed at infinity relative to the Sun. These trade-offs are fixed in Figure 2. The figure is presented ?? launch energy characteristic in terms of mission duration and launch date. A pulsed power plant with a fairly short duration of thrust is assumed. Planetary or solar flight is not assumed, only a direct launch to the object. It can be seen that there is a minimum of C3, which is about 26.5 km / s (703 km ^ 2 / s ^ 2). However, this minimum value quickly increases when the launch date is transferred to the future. At the same time, the long duration of the mission leads to a decrease in the required C3, but also implies a meeting with an asteroid at a greater distance from the Sun. The realistic launch date of the probe will be in the future at least 10 years (2027). At this moment, the hyperbolic excess speed is already 37.4 km / s (1400 km ^ 2 / s ^ 2) with a flight duration of about 15 years, which makes such a trajectory extremely difficult to accomplish during normal launches in the absence of a planetary span.

Figure 2: C3 characteristic energy relative to mission duration and launch date.

In addition to the hyperbolic excess speed at startup, the excess speed relative to the asteroid in a collision (V∞, 2) should be taken into account, since it determines the type of mission that is possible. High excess speed relative to the asteroid reduces the duration of the flight, but also reduces the time available for observations near the interstellar object. On the other hand, a low value for V∞, 2 may even allow a transition to an orbit around an asteroid with a pulsed or small maneuver to decelerate the probe. Excessive speed upon arrival is depicted in Figure 3, depending on the launch date and flight duration. The deformations of the velocity curves are due to the Earth’s orbit around the Sun, which leads to a more or less favorable position for launching toward the object. It can be seen that the minimum excess speed of about 26.75 km / s implies a launch in 2018 and a flight duration of more than 20 years. This value of excess speed does not prohibit the transition to orbit around 'Oumuamua. However, this minimum value increases rapidly for later launch dates. The realistic launch date of the probe will be from 5 to 10 years in the future (from 2023 to 2027). At this point, the required hyperbolic excess speed for the mission is from 33 to 76 km / s for a flight duration of 30 to 5 years. These values ​​greatly exceed the current capabilities of the chemical and electrical power plant to slow down and go into orbit around 'Oumuamua.

Figure 3: Hyperbolic excess speeds relative to flight duration and launch date

Figure 4 shows the approximate distance at which the spacecraft intercepts the object. For a realistic launch date of 2027 or later, the spacecraft flies past an object at a distance of 100 to 200 A from Earth, which is similar to the distance to Voyager probes today. At this distance, it is obvious that power supply and communications become a problem, and nuclear power sources, such as RTGs, are required.

Figure 4: Launch date and mission duration. The color code indicates the distance at which the spacecraft transmits the object.

Figure 5 shows the sample trajectory with the launch date in 2025. The Earth's orbit can be seen as a tiny ellipse around the Sun (indicated as a black circle) in the lower right corner of the picture. The trajectories of the asteroid and the spacecraft are almost straight.

Figure 5: Example of a spacecraft's trajectory for launch in 2025 and meeting with 1I / 'Oumuamua in 2055

Another suggestion is not to pursue Oumuamua, but to prepare for the next interstellar object to penetrate our solar system, developing the means to quickly launch a spacecraft to such an object.

Two scenarios were analyzed: first, a mission with a short duration of only a year, which would lead to a meeting of only 5.8 AU from the Sun. However, the required hyperbolic excess speed can reach a speed of about 20 km / s. Finally, due to the collision angle, a high speed is expected relative to the asteroid, amounting to 13.6 km / s, as shown in Figure 6.

Figure 6: Trajectory for launch in 2017 and meeting in 2018

The mission on the same launch date, but with a duration of 20 years, is shown in Figure 7. In a collision, the relative speed of a spacecraft relative to an object is relatively small (about 600 m / s for this particular case), which can be an opportunity to slow down the maneuver and go into orbit around 'Oumuamua.

Figure 7: Trajectory for launch in 2017 and meeting in 2037

In summary, the difficulty of achieving 'Oumuamua is a function of launching, hyperbolic excess speed and mission duration. Future mission developers need to find appropriate tradeoffs between these parameters. For a realistic launch date after 5-10 years, the hyperbolic excess speed ranges from 33 to 76 km / s with an encounter far from the limits of the Pluto orbit (50-200 ae).

3. Concepts and technologies

As shown above, the pursuit of 'Oumuamua with a realistic launch date (next 5-10 years) is a serious problem for modern space systems. A launch architecture is nominally possible using the Space Launch System (SLS), for example, which would simplify mission development. However, other launch providers also offer promising opportunities in the next few years. One of the potential opportunities is to use the Big Falcon (BFR) SpaceX rocket with the upper stage refueling in space with a launch date in 2025. To achieve the required hyperbolic excess (at least 30 km / s), a flyover of Jupiter in combination with a close passage near the Sun (up to 3 solar radii), nicknamed “solar fryby”, is necessary. This maneuver is also known by the “Oberth Maneuver” [5]. The architecture was proposed by the Keck Institute for Space Studies (KISS) [6] and the Jet Propulsion Laboratory (JPL) [7] for studying interstellar asteroids. However, the use of BFR eliminates the need for numerous gravitational maneuvers to create the impulse required to reach the trajectory of Jupiter. Instead, a direct launch of the probe with several accelerating steps ( with a highly elliptical near-earth orbit (Highly Eccentric Earth Orbit, HEEO ( ), which allows you to get a speed of 10 km / s for an 18-month journey to Jupiter and a gravitational maneuver for him, followed by the Sun around (which is necessary for changing the ecliptic.) Multi-layer thermal insulation protects the device from solar radiation when it turns on its solid-fuel engine with a large orbit perihelion (high thrust is needed to maximize the Oberth effect). the interstellar environment from the Keck Space Research Institute (KISS) showed the possibility of reaching the speed of 70 km / s with existing technologies and intercepting the body at a distance of 85 AU in 2039 if the apparatus was launched in 2025. More restrained estimates anyway allow you to accomplish a mission with a speed of 40 km / s and interception of an object at a distance of 155 AU in 2051. With a high convergence speed, the device will launch a shock probe, which should raise a significant cloud of gas, which can be a serious option for exploring leaving the asteroid with the spectrometer right on the spot. "

The above architecture emphasizes urgency, not advanced methods. The use of more advanced technologies, such as solar sails, laser sails and laser electrical movement, can open up additional opportunities for flight or rendezvous with the 'Oumuamua. Below are first-order analyzes for solar and laser sailing missions.

For the mission using the solar sail, it is supposed to launch from the Earth's orbit, taking into account the launch time from 3 to 4 years. The speed requirement is ~ 55 km / s, which indicates a luminance factor for a mission of 0.15 and a characteristic acceleration of 0.009 m / s ^ 2. This requires a specific load on the sail of the order of 1 g / m ^ 2, modern materials with light payloads can reach 0.1 g / m ^ 2. Given this, with different masses of spacecraft, assuming a sailing load up to 1 g / m ^ 2, we arrive at the values ​​given in Table 1 for circular and square sailing sailboats.

Table 1: Parameters of the solar sail in relation to the mass of the spacecraft
Spacecraft weight [kg] Sail area [m ^ 2] Ci

The most practical project involves the launch in 4 years and a ship weight of 1 kg and below.

The tasks based on lasers on the sails, based on the Stars Starshot technology “Breakthrough Initiatives” [8-10], will use a 2.74 MW laser beam with a full acceleration of the probe to 55 km / s and launch after 3.5 years (2021) , speeding up over 3000 with a probe weighing about 1 gram. He will reach 'Oumuamua in about 7 years. With a 27.4 MW laser, a 10 gram probe could be accelerated. Even larger masses of spacecraft can be achieved through the use of different mission architectures, lower acceleration speeds and a longer flight duration. However, with such an infrastructure with a laser beam, you could send hundreds or even thousands of probes, as shown in Figure 8. Such a distributed architecture using a swarm of probes will allow you to collect data on a larger search volume without limitation a single monolithic spacecraft.

Figure 8: Laser Sail Swarm (Image credit: Adrian Mann)

Another concept proposed by Strayan and Peck [11] is to send ChipSats to Jupiter's magnetosphere, and then using the Lorentz force, accelerate them to very high speeds of about 3000 km / s [12,11,13]. However, controlling the direction of these probes may not be a trivial task.

An important consequence is that after the operational infrastructure of the Beast Project Starshot is created, even on a small scale, missions to interstellar objects flying through the solar system can be launched in a short time and can justify the development of this infrastructure. The main advantage of such an architecture would be a short response time to unusual features. Investments will be justified by the optional cost of such infrastructure.

With regard to the deceleration on the object, you can obviously use existing motor systems, for example. although limited by low power density of RTGs as an energy source. ( It is not clear why nuclear reactors are not considered as an energy source. ) It is worth exploring more advanced technologies, such as magnetic sails [14,15], electric sails [16] and later magnetospheric braking system [17] with the distance between interceptions beyond the heliosphere , in the original interstellar medium (Interstellar Medium, ISM) . The technological readiness of these more advanced technologies is currently low, depends on breakthroughs in the production of superconducting materials, but they multiply the scientific return by orders of magnitude.

The small size of the object and its low albedo make it difficult to observe it after it again goes into deep space. This creates a significant navigation problem in order to get a fairly accurate direction to 'Oumuamua, in order to get closer to the object in order to collect useful data. Due to the positional uncertainty of such an object with a little-known trajectory, a project of a distributed mission should be investigated, using a swarm of probes that can cover a large area.

4. Conclusions

The discovery of the first interstellar object that visited our solar system is an exciting event and can be a chance for a lifetime or even several lives. To assess the possibility of achieving this object, i4is recently initiated the Lyra project. In this article, we have identified the key objectives for achieving 'Oumuamua, the approximate duration of the mission, and the necessary hyperbolic excess speed depending on the launch date. In any case, the mission of the object will stretch the boundaries of what is technologically possible today. A mission using a conventional chemical power system would have been feasible with a flyover of Jupiter for a gravitational maneuver and close passage near the Sun. Given the right materials, you can also use the technology of solar or laser sails.

An important result of our analysis is that the great value of the infrastructure of the laser beam from the Starshot Project “Breakthrough Initiatives” is flexibility that allows you to quickly respond to future unexpected events. For example, send a swarm of probes to the next object, similar to 'Oumuamua. If such infrastructure existed now, interception missions could reach 'Oumuamua within a year.

The future work of the Lyra project will focus on a more detailed analysis of the various concepts and technologies of the mission, in order to reduce their number to 2-3 promising options for further development.

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I apologize for the oversight at the initial publication.

Source: https://habr.com/ru/post/408425/

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