LTA Engineering & Flight Services
9 April 2007
Concept Technical Review
Ref: eXtreme Altitude Project (XAP)
The quest to make a serious, valuable, functional flight to 1 mb in the earth's atmosphere has been held back for the progress of technology as well as the state of materials and processing development. High altitude balloon flights encounter logarithmic resistance with altitude. The float altitude volumes become extremely large compared to the launch volumes. To strike a balance between the areal density of a balloon volume and the payload (manned or scientific) a combination of opportunities in all three areas previously cited is needed. The current proposed solution set forth by XAP offers a serious resolution to these problems, package in a form that has applications both in manned and unmanned versions. This project can provide application solutions to be utilized by civilian, military and government groups with requirements to operate in the mesosphere (near space) which is an area of high current use to these groups. The XAP solution to a mid-weight mesospheric flight includes use of established technology, novel solutions leveraged off of existing technology and operations solutions to earlier concerns with the ascent/descent mechanics of the cluster/Pleiades flight train configuration.
The main technical advancement created for and used by XAP is the Tubular Gore Tetroon (TGT). This represents advancement on tetroon technology on two fronts. These are the distribution of skin stress and the ease of manufacture. Existing tetroons are used for cost effective designs for inflatables as well as lower atmosphere applications. The ability to manufacture from a roll of material using a continuous sealing method offers many economies to a customer. The novel use of of an exterior tube to contain the lifting gas while at low altitudes and then expand to the center cavity as the balloon ascends helps keep the balloon material skin stress within manageable limits. The use of the tube with its smaller diameter also contributes to this skin stress management.
The manned use of the Pleiades flight configuration has been experimented with since the concept was put forth. In the last decade, the configuration has been seriously taken up by John Ninomiya with technical assistance from the XAP principle pilot. These efforts have resulted in significant altitude flights as well as a program that encompasses every state in the union (ongoing). The operational features of the earth based efforts have led to the resolution of initial flight train configuration, ascent and descent concerns that were present with early flights.
For manned flight configurations, the use of a hot air balloon as a decelerator is planned. The inflation of a balloon envelope while descending has been demonstrated on Earth as well as Venus. It is one of the core methods in the current Mars exploration efforts, as well. In the denser atmosphere of earth the deployment, filling, and subsequent decelerator function will be quite reasonable to achieve with a high degree of success. The option can be used or deleted for un-manned flight train configuration.
As with any collection of solutions the integration into a cohesive, cost effective, timely effort is the key to success. The development of the support team will be key to the success of this project. The requisite resources to support such a team are also key to the success of XAP.
The approach taken so far with the design, experimental verification of sub-components and sub-systems, leading to integration and test of the final system before committing to a value payload or manned flight is prudent and has been producing favorable results to date. Use of current technology tools for analysis has and can continue to provide thorough and cost effective analysis during the completion of the integration phases. Following the current project roadmap and plan should lead to a successful conclusion and safe flights into the mesosphere.
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