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Analysis Methods for Reusable Spacecraft Undergoing Aeroassist Maneuvers
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| 자료유형 | 학위논문 |
|---|---|
| 서명/저자사항 | Analysis Methods for Reusable Spacecraft Undergoing Aeroassist Maneuvers. |
| 개인저자 | Campbell, N. S. |
| 단체저자명 | University of Colorado at Boulder. Aerospace Engineering. |
| 발행사항 | [S.l.]: University of Colorado at Boulder., 2019. |
| 발행사항 | Ann Arbor: ProQuest Dissertations & Theses, 2019. |
| 형태사항 | 246 p. |
| 기본자료 저록 | Dissertations Abstracts International 81-05B. Dissertation Abstract International |
| ISBN | 9781088377185 |
| 학위논문주기 | Thesis (Ph.D.)--University of Colorado at Boulder, 2019. |
| 일반주기 |
Source: Dissertations Abstracts International, Volume: 81-05, Section: B.
Advisor: Argrow, Brian M. |
| 이용제한사항 | This item must not be sold to any third party vendors. |
| 요약 | Recent growth in commercial space operations provides exciting new challenges for the aerospace engineering community. In particular, increased orbital and sub-orbital activity represents high-speed flight design and mission planning efforts, which require the highest quality of predictive analysis tools to ensure safe and cost-effective performance. Along with the typical applications, such as ascent or entry, a recent proposal from United Launch Alliance (ULA) to re-use upper-stage spacecraft for in-space transportation services represents another application potentially requiring high-energy flight operations. The prospect of lunar-mined water promotes the establishment of in-space transportation infrastructure, which will enable the lunar mining market to receive supplies and send out product. Regular cargo transfers from the Earth-Moon Lagrange Point 1 (EML1) back to Low Earth Orbit (LEO) then motivates the use of aerobraking to save propellant or to increase payload mass fraction.Aerobraking is an aeroassist maneuver where atmospheric drag is used to decelerate and shed the necessary amount of excess velocity gained, in this case, while dropping in from EML1. Flight for such maneuvers occurs at high-altitudes where the atmospheric properties vary rapidly throughout the trajectory. Orbital vehicles entering an atmosphere have incredibly high kinetic energy, which results in nonequilibrium flowfields that exchange momentum and energy with the spacecraft surface in proportions that can depart from experience and intuition. In 2016, ULA teamed up with the University of Colorado to investigate these complexities and estimate the potential feasibility and benefits of aerobraking their next generation upper stage. Preliminary estimates predicted 90% of propellant could be saved using aerobraking in the transfer from EML1 to LEO (as compared to a fully propulsive transfer). However, this estimate did not provide an accurate or precise look into the thermal response of the spacecraft.In this work, the concept of aerobraking a vehicle resembling ULA's planned Advanced Cryogenic Evolved Stage (ACES) spacecraft is investigated. In order to estimate the amount of heat being absorbed during aerobraking, the author implemented and coupled models for the underlying loads on the vehicle, the resulting flight trajectories based on various orbital states and spacecraft configurations, and the thermal response of the spacecraft structure. Any energy transferred to the cryogenic propellant results in boil-off leading to wasted propellant when vented to maintain tank pressures below structural limits. Since it is also important to ensure wall temperatures stay below material limits, the prospect of using gaseous propellant to cool the body before being vented, is also considered. Where necessary, new methods were developed.Multi-mode heat transfer models that can incorporate results from an aerospace loads database and couple to an aerobraking trajectory solver were investigated in order to compare spacecraft-component material selections and the effect of targeted cooling on different sections of the three-dimensional wall geometry. An Augmented Temperature (AT) model was devised to estimate a traditional, fully discrete solution to the conservation of energy in the spacecraft's structure. Tests performed with simple geometries show the AT model can provide precise estimates in a number of cases while remaining conservative in regions of identified breakdown. Most importantly, the method enables the coupled trajectory-thermal response models to solve in less time than the fully discrete solution, by orders of magnitude. This enables large batches of trajectories to be computed in a timely fashion. As a result, more design configurations or cooling options can be tested in a given amount of time. To put this benefit into context, for a batch computation of 750 aerobraking trajectories of a sphere discretized to 104 elements, the traditional scheme would take just under six days to complete. The AT method for this same surface mesh would be expected to take only nine minutes.In the end, an extensive set of simulated aerobraking trajectories enabled a trade study regarding various ACES configurations making the orbital transfer from EML1 to LEO. This trade study reveals the importance of a decreased vehicle ballistic coefficient, on-board cooling options, and targeting strategy on the resulting propellant savings. Savings are defined relative to a standard, propulsive transfer. Targeting motor efficiency is also shown to be an important factor, especially if short duration transfers are desired. Only ballistic, fixed-attitude trajectories were investigated, as they provide a worst-case representation of feasible aerobraking corridors. Overall, this culminated in a number of cases showing savings of 10% and greater. In a few cases, values of over 50% savings were realized, with the maximum case being 72% savings. |
| 일반주제명 | Aerospace engineering. |
| 언어 | 영어 |
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