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Putting the Propellant in the Fuel Tank
Abstract
Gateway Earth Development Group is an initiative proposing new modular space access architecture, centred on operating
a combined research space station and commercial space hotel in the geostationary orbit (GEO) – the Gateway Earth
complex. At this location, robotic and crewed interplanetary spacecraft could be assembled, and docked before they travel
to, and return from, any Solar System destination. Moreover, it is proposed that space tourism would provide a significant
part of the funding to build and maintain the complex. In order to do so, various elements of this architecture, which are
currently being developed independently by a range of different space firms and agencies, both internationally and in the
UK, need to be integrated into a single mission proposal. Hence, it is our aim at GEDG to synthesize all these disparate
actors and activities, and focus them on making the Gateway Earth concept possible in the mid-term future. This paper
provides a status update on these projects’ progress to date and focuses on the next steps required to ensure this concept
becomes an accepted architecture for space access and exploration. The aim is to establish the Gateway Earth approach
as a preferred technically-feasible and politically and financially realistic concept and thereby enable a new generation of
affordable space exploration missions, backed by revenues generated from commercial space activities.
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Gateway Earth Development Group seeks to design a technically and economically viable architecture for interplanetary space exploration. We are proposing to utilise space tourism as an enabler for the development of a space station in Earth’s geostationary orbit (GEO), at which interplanetary spacecraft could be build and serviced to take astronauts on missions across the Solar System. Access to this space gateway will be provided by deploying re-usable vehicles, which will in stages - through Low Earth Orbit (LEO) - deliver goods and people to the station.
Gateway Earth itself will be a combined governmental space station and commercial space hotel, located in GEO. At this location it is close to the edge of Earth’s “gravity well”, and so it is a great place for interplanetary spacecraft to dock both as they depart for, and as they return from, distant Solar System destinations. This would apply to both robotic and crewed missions. For the same reason it is a great place to assemble the interplanetary craft, which would then avoid the craft having to withstand the rigors of launch and re-entry through Earth’s atmosphere. Space tourism revenues will provide a significant part of the funding needed to both build the complex and supply the regular reusable tug service.
At present, various elements of the concept are being developed independently by different space engineering firms and agencies; some large, and others small and entrepreneurial in nature. Our aim is to synthesize all these disparate activities, and have them focus on making the overall Gateway Earth concept possible. This paper will provide a status update on progress to date and invite feedback on key modules of the projects’ architecture.
Gateway Earth is proposed as modular space access architecture, operating a combined governmental space station and commercial space hotel located in the geostationary orbit [1, 2]. This location, close to the edge of the Earth's "gravity well", is ideal for robotic and crewed interplanetary spacecraft to dock as they depart for, or return from, any Solar System destinations. Additionally, assembling interplanetary craft, almost certainly including in-situ (additive) manufactured components, at this location would avoid these vehicles having to withstand the rigors of launch and re-entry through Earth's atmosphere. Moreover, space tourism revenues will provide a significant part of the funding needed to both build the complex and supply the regular reusable tug service via low-earth orbit [3]. Various elements of the architecture are being developed independently by a whole range of different space engineering firms and national and international agencies; some large, and others small and entrepreneurial in nature. Our aim is to synthesize all these disparate activities, and have them focus on making the overall Gateway Earth concept possible and deliverable in the mid-term future [4]. This paper is providing a status update on Gateway Earth Development Group's progress to date and invites feedback on key modules of the architecture as well as Gateway Earth's overall development and operational strategy.
Uncertainties in estimating health risks from galactic cosmic rays are a major limitation to the
length of space missions and the evaluation of potential risk mitigations. NASA limits astronaut
exposures to a 3% risk of exposure-induced death (REID) and protects against uncertainties in
risks projections using an assessment of 95% confidence intervals in the projection model. Revisions
to the NASA projection model for lifetime cancer risks from space radiation and new estimates
of model uncertainties are described in this report. Our report first reviews models of space
environments and transport code predictions of organ exposures, and characterizes uncertainties
in these descriptions. We then summarize recent analysis of low linear energy transfer (LET)
radio-epidemiology data, including revision to the Japanese A-bomb survivor dosimetry, longer
follow-up of exposed cohorts, and reassessments of dose and dose-rate reduction effectiveness
factors (DDREFs). We compare these newer projections and uncertainties with earlier estimates
made by the National Council of Radiation Protection and Measurements (NCRP). Current understanding
of radiation quality effects and recent data on factors of relative biological effectiveness
(RBE) and particle track structure are then reviewed. Recent results from radiobiology experiments
from the NASA Space Radiation Laboratory provide new information on solid cancer and leukemia
risks from heavy ions, and radiation quality effects are described. We then consider deviations
from the paradigm of linearity at low doses of heavy ions motivated by non-targeted effects
(NTE) models. Recommendations to improve the NSCR 2010 model by the National Research
Council216 are included in several sections of this report as outlined in the Preface, and denoted
as the NSCR 2012 model.
The new findings and knowledge are used to revise the NASA risk projection model for space
radiation cancer risks. Key updates to the model are:
1) Revised values for low-LET risk coefficients for tissue-specific cancer incidence. Tissuespecific
incidence rates are then transported to an average U.S. population and used to
estimate the probability of risk of exposure-induced cancer (REIC) and REID.
2) An analysis of lung cancer and other smoking-attributable cancer risks for neversmokers
that shows significantly reduced lung cancer risks as well as overall cancer
risks compared to risk estimated for the average U.S. population.
3) A new approach to radiation quality factors (QFs) based on: i) Derivation of trackstructure-
based radiation quality functions that depend on charge number, Z, and kinetic
energy, E, in place of a dependence on LET alone. ii) The assignment of a smaller
maximum in the quality function for leukemia than for solid cancers. iii) Development of
probability distribution functions (PDFs) for QF that have a higher importance than their
central estimates, the QF itself, and suggests research approaches to narrow QF
uncertainties.
4) The use of the International Commission on Radiological Protection tissue weights is
shown to overestimate cancer risks from solar particle events (SPEs) by a factor of 2 or
more. Summing cancer risks for each tissue is recommended as a more accurate approach
to estimate SPE cancer risks. However, gender-specific tissue weights are recommended
to define Effective doses as a summary metric of space radiation exposures.
5) Revised uncertainty assessments for all model coefficients in the risk model (physics,
low-LET risk coefficients, DDREF, and QFs), and an alternative uncertainty assessment
that considers deviation from linear responses as motivated by NTE models.
6) Models to support probabilistic risk assessment (PRA) for space radiation risks are
described.
What will happen to the near-Earth space environment? How can we ensure the survival of future scientific, commercial and military satellites and space stations? This book addresses the questions that must be asked as man-made debris in space around the Earth - from dust particles to rocket casings, and even radioactive materials - becomes a critical problem. World wide specialists address the issues, problems and policies concerned with the preservation of near-Earth space in this volume. Their articles cover the technical aspects, and the economic and legal issues concerned, including the enforcement and monitoring of international agreements and the resolution of disputes. This clearly written and well-illustrated survey offers the professional and concerned non-specialist an authoritative review of the problems with, and solutions to, space debris.
The term "Kessler Syndrome" is an orbital debris term that has become popular outside the professional orbital debris community without ever having a strict definition. The intended definition grew out of a 1978 JGR paper predicting that fragments from random collisions between catalogued objects in low Earth orbit would become an important source of small debris beginning in about the year 2000, and that afterwards, "...the debris flux will increase exponentially with time, even though a zero net input may be maintained". The purpose of this paper is to clarify the intended definition of the term, to put the implications into perspective after 30 years of research by the international scientific community, and to discuss what this research may mean to future space operations. The conclusion is reached that while popular use of the term may have exaggerated and distorted the conclusions of the 1978 paper, the result of all research to date confirms that we are now entering a time when the orbital debris environment will increasingly be controlled by random collisions. Without adequate collision avoidance capabilities, control of the future environment requires that we fully implement current mitigation guidelines by not leaving future payloads and rocket bodies in orbit after their useful life. In addition, we will likely be required to return some objects already in orbit.
This paper sets space tourism in its historic setting, while looking
ahead to where it may lead, and it underlines the significance of the
new space tourism services to the overall future of the utilization of
space, whether for commercial or governmental purposes.
The establishment of a long‐term, low Earth orbiting outpost has long been a goal of space exploration advocates. A variety of orbiting space stations, envisioned by writers, engineers, and scientists for years, have been developed, launched, and deorbited. The Soviet Union and Russia have flown several Salyut stations and only recently terminated operations of the Mir Space Station. The United State flew three missions on the Skylab Space Station that was launched in 1975.
The long developmental history of the International Space Station (ISS) includes many lessons and are discussed. The huge scale of the project offers many engineering, policy, and management lessons for our future endeavors in space. Despite the many challenges and the long development period, the project is now demonstrating great success an overview of the configuration of the ISSW given. The segments contributed by the U.S., Russia, Canada, Europe, and Japan are detailed. These partners have formulated a share agreement to allocate all of the critical ISS resources. In November 2000, the first permanent crew docked with and entered the International Space Station. Since then, the International team has continued to outfit and augment the ISS. At this time, the fifth expedition crew is well into their stay on board the ISS. The results of many years of painstaking work are evident as the ISS flies overhead.
OLTARIS (On-Line Tool for the Assessment of Radiation In Space) is a space radiation analysis tool available on the World Wide Web. It can be used to study the effects of space radiation for various spacecraft and mission scenarios involving humans and electronics. The transport is based on the HZETRN transport code and the input nuclear physics model is NUCFRG. This paper describes the tools behind the web interface and the types of inputs required to obtain results. Typical inputs are mission parameters and slab definitions or vehicle thickness distributions. Radiation environments can be chosen by the user. This paper describes these inputs as well as the output response functions including dose, dose equivalent, whole body effective dose equivalent, LET spectra and detector response models.
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