Deflection Missions Research Articles

Investigation of the incremental benefits of eccentric collisions in kinetic deflection of potentially hazardous asteroids

In asteroid momentum deflection missions, the presence of ejecta leads to a phenomenon where the system’s momentum appears “amplified” after the impact. This paper makes use of this phenomenon and demonstrates through computational simulations that targeting a point off the geometric center of an asteroid can further enhance the collisional benefit after impact. Due to uncertainties in the attitude of the asteroid and the momentum transfer coefficient (β,γ), this study employs a Monte Carlo approach to address these uncertainties. The results indicate that the strategy proposed in this paper can increase the post-collision deflection distance of the asteroid relative to Earth by an average of 81.05%, while also reducing the standard deviation by an order of magnitude, significantly lowering the uncertainty of the deflection mission. Furthermore, the results show that for certain asteroids particularly sensitive to changes in velocity Δv, blindly targeting their geometric center could result in a 48% probability of reducing the minimum distance to Earth. However, the striking strategy developed in this study can avoid this negative outcome. Finally, based on the computational results, a statistical formula is derived to predict the relative gain of the two strategies, concluding that for asteroids with smaller semi-major axes a, and the interception angle α at impact is greater, the benefits of employing the approach discussed in this paper are greater.

Developing algorithms to determine an Asteroid’s physical properties and the success of deflection missions

The rate of discovery of near-Earth asteroids currently outpaces our ability to analyze them. Knowledge of an asteroid's physical properties is essential to deflect them. I developed free and open-source algorithms and training modules. These tools utilize images from robotic telescopes, open-source data, and high school-level mathematics to determine asteroids' size, rotation period, and strength. I took observations of the Didymos binary asteroid, and my algorithm determined its size to be 850 ± 0.04 m, with a 2.261 ± 0.018 h rotation period and rubble-pile strength. I measured a decrease in the mutual orbital period after impact by NASA's 2022 DART Mission, confirming successful deflection. My findings matched closely with those obtained by NASA and external sources (Daly et al., 2023; Thomas et al., 2023; Talbert, 2022, October 11; Nakanoet al., 2022) [1,2,3,4]. Every young person and citizen scientist can now be a planetary defender.

Measurability of the Heliocentric Momentum Enhancement from a Kinetic Impact: The Double Asteroid Redirection Test (DART) Mission

The NASA Double Asteroid Redirection Test (DART) has demonstrated the capability of successfully conducting kinetic impact-based asteroid deflection missions. The changes in the Didymos–Dimorphos mutual orbit as a result of the DART impact have already been measured. To fully assess the heliocentric outcome of deflection missions, the heliocentric momentum enhancement parameter, β ⊙, needs to be determined and disentangled from other nongravitational phenomena such as the Yarkovsky effect. Here we explore the measurability of β ⊙ resulting from DART, which we estimate simultaneously with nongravitational accelerations using a least-squares filter. Results show that successful stellar occultation measurements of the Didymos system in the second half of 2024 in addition to the ones in the 2022–2023 campaigns can achieve a statistically significant estimate of β ⊙, with an uncertainty slightly above 20% for an assumed β ⊙ = 3. Adding additional occultation measurements and pseudorange measurements from the Hera spacecraft operations at Didymos starting in 2027 decreases this relative uncertainty to under 6%. We find that pre-impact occultation observations combined with post-impact occultations would have yielded substantially higher signal-to-noise ratios on the heliocentric deflection. Additionally, pre-impact occultations would also have enabled a statistically significant β ⊙ estimate using only one additional occultation in 2023 September. Therefore, we conclude that future asteroid deflection missions would greatly benefit from both pre- and post-deflection occultation measurements to help assess the resulting orbital changes.

Legal considerations on a regional security organization for planetary defence

Under the UN-Charter system, the maintenance of international peace and security is traditionally the primary responsibility of the UN Security Council as set forth in Chapter VII. Since the Security Council's competence for dealing with matters of international peace and security is not exclusive, other international bodies may take a role in addressing threats emanating from outer space. A regional security organization for planetary defence can be established under Article 52 UN-Charter and may provide for an alternative forum to decide upon the necessary steps for Near Earth Object (NEO)-deflection missions. The international legal personality of an international organization for planetary defence leads to the capacity of entering into treaties, the international responsibility for acts and omissions attributed to it and the enjoyment of privileges and immunities. Such organization can also declare acceptance of the UN Space Treaties.

Targets selection and mission optimization of kinetic impact deflection test mission for small size asteroids

Near-Earth Asteroids (NEAs) impact poses a major potential threat to life on Earth, and kinetic impact is currently the most mature and feasible means of asteroid defense. The deflection effect of kinetic impact (KI) is closely related to the asteroid orbit, structure, material composition, mechanical properties, impact velocity, and other factors. To ensure the success of an asteroid defense mission, it is crucial to conduct in-orbit test missions and gain a thorough understanding of momentum transfer and orbital deflection principles. The Double Asteroid Redirection Test (DART) Mission has been launched and successfully impacted the Dimorphos whose diameter is 160 m. However, missions specifically targeting near-Earth asteroids with diameters ranging from 20 m to 90 m, which are more abundant but fainter and pose greater challenges in terms of navigation and guidance accuracy, have not been executed. For in-orbit demonstration and performance evaluation of kinetic impact asteroid deflection missions, the selection criteria for candidate asteroids were first established considering the size, orbit distribution, orbit uncertainty, characteristic information, and optical observability. 20 near-Earth asteroids were selected as primary candidate asteroids from the 28,946 cataloged near-Earth asteroids. Then, according to the mission cost and the way to evaluate the deflection distance, two Kinetic Impact in-orbit Demonstration (KID) mission scenarios were designed. A kinetic impact test mission optimization model was developed, integrating global and local optimization algorithms, while considering constraints like launch vehicle, launch site, and observability during and after impact. The model utilized a high-precision orbital dynamics model of the solar system to assess the deflection effect on the asteroid. We further reduced the candidate asteroids to 7 and ranked them in each mission scenario. Additionally, disruption conditions of the asteroids were examined, and mission parameters were re-optimized to ensure deflection without disruption. Accounting for factors such as the momentum enhancement factor, the impact probability between the asteroid and Earth was calculated for a 200-year period following the impact, thus evaluating the risk of an asteroid colliding with Earth after the KID mission implementation. The research can provide references for the target selection and kinetic impact test mission options for 20–90 m asteroids.

After DART: Using the First Full-scale Test of a Kinetic Impactor to Inform a Future Planetary Defense Mission

NASA’s Double Asteroid Redirection Test (DART) is the first full-scale test of an asteroid deflection technology. Results from the hypervelocity kinetic impact and Earth-based observations, coupled with LICIACube and the later Hera mission, will result in measurement of the momentum transfer efficiency accurate to ∼10% and characterization of the Didymos binary system. But DART is a single experiment; how could these results be used in a future planetary defense necessity involving a different asteroid? We examine what aspects of Dimorphos’s response to kinetic impact will be constrained by DART results; how these constraints will help refine knowledge of the physical properties of asteroidal materials and predictive power of impact simulations; what information about a potential Earth impactor could be acquired before a deflection effort; and how design of a deflection mission should be informed by this understanding. We generalize the momentum enhancement factor β, showing that a particular direction-specific β will be directly determined by the DART results, and that a related direction-specific β is a figure of merit for a kinetic impact mission. The DART β determination constrains the ejecta momentum vector, which, with hydrodynamic simulations, constrains the physical properties of Dimorphos’s near-surface. In a hypothetical planetary defense exigency, extrapolating these constraints to a newly discovered asteroid will require Earth-based observations and benefit from in situ reconnaissance. We show representative predictions for momentum transfer based on different levels of reconnaissance and discuss strategic targeting to optimize the deflection and reduce the risk of a counterproductive deflection in the wrong direction.

Heliocentric Effects of the DART Mission on the (65803) Didymos Binary Asteroid System

The Double Asteroid Redirect Test (DART) is NASA’s first kinetic impact–based asteroid deflection mission. The DART spacecraft will act as a projectile during a hypervelocity impact on Dimorphos, the secondary asteroid in the (65803) Didymos binary system, and alter its mutual orbital period. The initial momentum transfer between the DART spacecraft and Dimorphos is enhanced by the ejecta flung off the surface of Dimorphos. This exchange is characterized within the system by the momentum enhancement parameter, β, and on a heliocentric level by its counterpart, β ⊙. The relationship between β and the physical characteristics of Dimorphos is discussed here. A nominal set of Dimorphos physical parameters from the design reference asteroid and impact circumstances from the design reference mission are used to initialize the ejecta particles for dynamical propagation. The results of this propagation are translated into a gradual momentum transfer onto the Didymos system barycenter. A high-quality solar system propagator is then used to produce precise estimates of the post-DART encounters between Didymos and Earth by generating updated close approach maps. Results show that even for an unexpectedly high β ⊙, a collision between the Didymos system and Earth is practically excluded in the foreseeable future. A small but significant difference is found in modeling the overall momentum transfer when individual ejecta particles escape the Didymos system, as opposed to imparting the ejecta momentum as a single impulse at impact. This difference has implications for future asteroid deflection campaigns, especially when it is necessary to steer asteroids away from gravitational keyholes.

Centroiding method for small celestial bodies with unknown shape and small size

Focused on small celestial body deflection missions using a kinetic impactor spacecraft, we propose a method for estimating the center of small objects with unknown shape and small size, which relaxes the requirement for prior information of the object shape model and lowers the risk of missing the target. The impact center is inferred using the visible part of the object in a single image. In the first step, the illuminated part of the object’s true contour is segmented from the whole contour extracted from the image based on the prior information of the illumination direction. In the second step, the concave–convex characteristic of the illuminated contour is identified. In the third step, one of two modes, moment estimation or skeleton center estimation, is chosen based on the concave–convex characteristic to calculate the impact center. The proposed algorithm was verified by a simulation study under various conditions. Due to the problems of the unknown model shapes of small objects and complex illumination conditions in kinetic impact missions, the proposed centroiding algorithm will play an important role.

Assembled kinetic impactor for deflecting asteroids by combining the spacecraft with the launch vehicle upper stage

Asteroid impacts pose a major threat to all life on Earth. Deflecting an asteroid on an impact trajectory is critical to mitigating this threat. A kinetic impactor remains the most feasible asteroid deflection method. However, due to launch capability constraints, an impactor with a limited mass can only minimally change the velocity of an asteroid. To improve the deflection efficiency of the kinetic impactor strategy, this paper proposes the Assembled Kinetic Impactor (AKI), which combines the spacecraft with the launch vehicle upper stage. After the launch vehicle upper stage sends the spacecraft into an Earth-escaping trajectory, the spacecraft-rocket separation is not performed, and the spacecraft controls the AKI to impact the asteroid. By retaining the mass of the launch vehicle upper stage, the mass of the impactor is increased, thereby enhancing the deflection efficiency. According to the technical data of the Long March 5 (CZ-5) launch vehicle, missions to deflect Bennu are designed to demonstrate the power of the AKI concept. Simulation results of the AKI compared with the Classical Kinetic Impactor (CKI, with spacecraft-rocket separation) show that the addition of the mass of the upper stage increases the deflection distance by >3 times. To achieve a given deflection distance, the addition of the upper stage mass reduces the number of launches to 1/3 that of the number of CKI launches. The AKI concept makes it possible to deflect large Bennu-like asteroids with a nuclear-free technique with a 10-year launch lead time. Additionally, with a single CZ-5, the deflection distance of a 140-m-diameter asteroid with a 10-year launch lead time increases from less than 1 to more than 1 Earth radius, representing an improvement in the reliability and efficiency of asteroid deflection missions.

Deflection driven evolution of asteroid impact risk under large uncertainties

The threat of asteroid impacts on the Earth can be mitigated through deflection missions. The deflection capability has previously been omitted in asteroid impact risk analysis work that quantifies impact damage on the Earth. Here we investigate the effect of pre-designed deflection missions on the risk profile of the fictitious impact scenario 2019 PDC. The impact risk analysis is based on a statistical approach. We sample orbital and physical property distributions that provide a complete representation of possible impact scenarios. Three pre-designed kinetic impactor deflection missions are considered in separate simulations. The deflection mission imposes a deflection ΔV on the asteroid and the impulse enhancement factor β is calculated as part of the analysis. The post-deflection impact risk is compared to the undeflected risk situation. Variations in physical and orbital properties make the outcome of deflection missions uncertain. It can therefore be inadequate to label deflection mission outcomes in binary terms of success and failure. Instead, defining a satisfactory risk reduction goal and scaling the deflection mission capability to deliver this risk reduction is more accurate. In addition, the results highlight dilemmas that decision-makers would face in an asteroid threat scenario. By implementing a deflection mission, the potential impact point of the asteroid is moved, threatening new populations and potentially increasing damage in case of an impact.

Hybrid PID-FUZZY Control of Formation Flying of Spacecrafts in order to asteroid Deflection Mission

Hybrid PID-FUZZY Control of Formation Flying of Spacecrafts in order to asteroid Deflection Mission

Measuring ejecta characteristics and momentum transfer in experimental simulation of kinetic impact

The characteristics of ejecta are the crucial element in the concept of kinetic impact deflection of asteroids. The mass and velocity distribution of particles ejected from the impact site determine the enhancement of the momentum transferred by the kinetic impact spacecraft to the target body. Laboratory experiments provide an important means of investigating ejecta characteristics [1] and substantially contribute to the evaluation of deflection efficiency. Scaling laws derived from dimensional analysis and experiments, performed mainly in the context of cratering research [2], have been used to assess the kinetic impact deflection technique [3], [4]. In view of future real-scale deflection missions, like the planned NASA DART impact, more dedicated experiments at relevant impact conditions may substantially contribute to analyzing impact effects, validating numerical simulations and, finally, designing a mission.We performed scaled hypervelocity experiments with impact conditions similar to currently discussed full-scale kinetic impact demonstration missions like DART. In particular, we directly measured both the ejecta characteristics and the momentum transfer in these experiments. The objective of these initial experiments was to demonstrate a novel method for individual particle tracking in the context of asteroid deflection. By determining the size and the velocity of individual particles, we can directly study their influence on the momentum enhancement, the total amount of which we measured using a well-established ballistic pendulum.

Deflection of fictitious asteroid 2017 PDC: Ion beam vs. kinetic impactor

Mission scenarios for the deflection of fictitious asteroid 2017 PDC are investigated. Two deflection options, kinetic impactor (KI) and ion beam shepherd (IBS), are studied and compared on the basis of deflection performance, safety, as well as mission schedule and political aspects. Firstly, we propose the launch of a medium-size rendevous spacecraft equipped with at least two ionic thrusters that can serve as propulsion means for the interplanetary trajectory up to rendezvous with the asteroid and as contactless actuators for a possible follow-up deflection mission. The asteroid, whose uncertainty ellipsoid is initially too large to establish whether (and how) it should be deflected, is reached by the rendezvous spacecraft after a low-thrust interplanetary trajectory of reasonable duration. Following rendezvous the spacecraft is placed in the vicinity of the asteroid to estimate its mass, study its structure and composition and, crucially, reduce its uncertainty ellipsoid by ground tracking to confirm or rule out an impact. Assuming that an impact is confirmed two main deflection scenarios are considered based on the actual asteroid size. Ion beam deflection is considered with the possibility of full deflection (the asteroid misses the Earth by a safe margin) or impact location adjustment (the impact footprint is diplaced to the nearest unpopulated region) depending on the asteroid size and the predicted impact location. The launch of a kinetic impactor mission is also considered with the employment of the rendezvous spacecraft to measure the deflection outcome and possibly to refine the deflection in case it is needed. The deflection performance of the two methods is compared.

Rotational and translational considerations in kinetic impact deflection of potentially hazardous asteroids

Kinetic impact may be the most reliable and easily implemented method to deflect hazardous asteroids using current technology. Depending on warning time, it can be effective on asteroids with diameters of a few hundred meters. Current impact deflection research often focuses on the orbital dynamics of asteroids. In this paper, we use the ejection outcome of a general oblique impact to calculate how an asteroid’s rotational and translational state changes after impact. The results demonstrate how small impactors affect the dynamical state of small asteroids having a diameter of about 100m. According to these consequences, we propose using several small impactors to hit an asteroid continuously and gently, making the deflection mission relatively flexible. After calculating the rotational variation, we find that the rotational state, especially of slender non-porous asteroids, can be changed significantly. This gives the possibility of using multiple small impactors to mitigate a potentially hazardous asteroid by spinning it up into pieces, or to despin one for future in-situ investigation (e.g., asteroid retrieval or mining).

Modeling impact outcomes for the Double Asteroid Redirection Test (DART) mission

The Double Asteroid Redirection Test (DART) is a NASA mission concept currently in Phase-A study, which will provide the first full-scale test of a kinetic impactor deflection mission for planetary defense. The DART spacecraft will target the moon of Didymos (Didymos-B, or “Didymoon”) and impact the smaller body at ~6 km/s with ~500 kg mass. The change in orbital period of the moon will then be measured using ground-based observations, which can be used to estimate the momentum enhancement of the moon from the impact. Impact modeling provides a basis for interpretation of the DART impact and observations (including the calculation of the momentum enhancement, β, the period change, and ejecta mass for a given impact scenario). Here, we present results from simulations using the shock physics codes CTH and Spheral of a DART-like impact into an asteroid target. Variations in target composition and porosity are simulated to examine their effect on β. A variety of methods are used to calculate β, and these simulations suggest that β can be calculated using any of them, depending on what type of simulation is performed, and provide consistent results. The results also indicate that varying the target composition (e.g., whether the target is made up of something granite-like or more akin to basalt or pumice) does not significantly affect the results. More significant changes are seen when parameters such as porosity are varied: increased porosity decreases β, alters the crater shape, and increases ∆v. Simulations also suggest that the form of porosity is important: macro-porosity has a significant effect on the cratering process that is different than equivalent micro-porosity.

Effect of the finite size of an asteroid on its deflection using a tether–ballast system

Potentially hazardous near-Earth objects which can impose a significant threat on life on the planet have generated a lot of interest in the study of various asteroid deflection strategies. There are numerous asteroid deflection techniques suggested and discussed in the literature. This paper is focused on one of the non-destructive asteroid deflection strategies by attaching a long tether–ballast system to the asteroid. In the existing literature on this technique, very simplified models of the asteroid-tether–ballast system including a point mass model of the asteroid have been used. In this paper, the dynamical effect of using a finite size asteroid model on the asteroid deflection achieved is analyzed in detail. It has been shown that considering the finite size of the asteroid, instead of the point mass approximation, can have significant influence on the deflection predicted. Furthermore the effect of the tether-deployment stage, which is an essential part of any realistic asteroid deflection mission, on the predicted deflection is studied in this paper. Finally the effect of cutting the tether on the deflection achieved is analyzed and it has been shown that depending on the orbital properties of the asteroid as well as its size and rotational rate, cutting the tether at an appropriate time can increase the deflection achieved. Several numerical examples have been used in this paper to elaborate on the proposed technique and to quantitatively analyze the effect of different parameters on the asteroid deflection.

Electric Solar Wind Sail Kinetic Energy Impactor for Asteroid Deflection Missions

An electric solar wind sail uses the natural solar wind stream to produce low but continuous thrust by interacting with a number of long thin charged tethers. It allows a spacecraft to generate a thrust without consuming any reaction mass. The aim of this paper is to investigate the use of a spacecraft with such a propulsion system to deflect an asteroid with a high relative velocity away from an Earth collision trajectory. To this end, we formulate a simulation model for the electric solar wind sail. By summing thrust vectors exerted on each tether, a dynamic model which gives the relation between the thrust and sail attitude is proposed. Orbital maneuvering by fixing the sail’s attitude and changing tether voltage is considered. A detailed study of the deflection of fictional asteroids, which are assumed to be identified 15 years before Earth impact, is also presented. Assuming a spacecraft characteristic acceleration of 0.5 mm/s 2, and a projectile mass of 1,000 kg, we show that the trajectory of asteroids with one million tons can be changed enough to avoid a collision with the Earth. Finally, the effectiveness of using this method of propulsion in an asteroid deflection mission is evaluated in comparison with using flat photonic solar sails.

On the possibility of using small asteroids for deflecting near-Earth asteroids

This paper presents the trajectory design and analysis of the near-Earth asteroid (NEA) deflection mission enabled by a kinetic impact of an intermediate asteroid. The sequential transfer trajectory is designed by solving two Lambert’s problems that yield a chain collision between a spacecraft and an intermediate asteroid, followed by a collision between the intermediate asteroid and an NEA. The characteristics of the low-cost trajectories are then identified with respect to the optimal collision point. We show that the feasibility of the mission depends on the existence of an intermediate asteroid with small minimum orbit interception distance (MOID) with the NEA. Moreover the selection strategy of an intermediate asteroid that makes the mission feasible is discussed. We show that several asteroids exist that allow a 10ton spacecraft with limited ΔV to be launched and impact the NEA 99442 Apophis allowing a deflection given several years warning time.

Post mitigation impact risk analysis for asteroid deflection demonstration missions

Even though mankind believes to have the capabilities to avert potentially disastrous asteroid impacts, only the realization of mitigation demonstration missions can validate this claim. Such a deflection demonstration attempt has to be cost effective, easy to validate, and safe in the sense that harmless asteroids must not be turned into potentially hazardous objects. Uncertainties in an asteroid’s orbital and physical parameters as well as those additionally introduced during a mitigation attempt necessitate an in depth analysis of deflection mission designs in order to dispel planetary safety concerns. We present a post mitigation impact risk analysis of a list of potential kinetic impactor based deflection demonstration missions proposed in the framework of the NEOShield project. Our results confirm that mitigation induced uncertainties have a significant influence on the deflection outcome. Those cannot be neglected in post deflection impact risk studies. We show, furthermore, that deflection missions have to be assessed on an individual basis in order to ensure that asteroids are not inadvertently transported closer to the Earth at a later date. Finally, we present viable targets and mission designs for a kinetic impactor test to be launched between the years 2025 and 2032.

Estimation of necessary laser power to deflect near-Earth asteroid using conceptual variable-laser-power ablation

In this research, the necessary laser power to deflect a near-Earth asteroid (NEA) is estimated using a future conceptual variable-laser-power ablation technique. The required necessary laser power is approximated by the established system dynamics that considers a conceptual on-board laser tool, which can vary the laser power output within a certain range to ablate an object's surface. Using established system dynamics, the necessary laser power (both the maximum and minimum values), action direction and action duration with respect to various action start times are successfully estimated. These estimates are significantly lower than those assumed in previous studies. In addition, the effectiveness of deflections using a time-varying laser power within a certain range by controlling both laser action directions is discussed. The method described in this work is expected to be useful in approximating the necessary laser power with regard to various operation start times for future deflection missions with space-based laser ablation tools provided by any type of power source.