Fully autonomous navigation for the NASA cargo transfer vehicle

A great deal of attention has been paid to navigation during the close approach (less than or equal to 1 km) phase of spacecraft rendezvous. However, most spacecraft also require a navigation system which provides the necessary accuracy for placing both satellites within the range of the docking sensors. The Microcosm Autonomous Navigation System (MANS) is an on-board system which uses Earth-referenced attitude sensing hardware to provide precision orbit and attitude determination. The system is capable of functioning from LEO to GEO and beyond. Performance depends on the number of available sensors as well as mission geometry; however, extensive simulations have shown that MANS will provide 100 m to 400 m (3(sigma)) position accuracy and 0.03 to 0.07 deg (3(sigma)) attitude accuracy in low Earth orbit. The system is independent of any external source, including GPS. MANS is expected to have a significant impact on ground operations costs, mission definition and design, survivability, and the potential development of very low-cost, fully autonomous spacecraft

The Sprite Mini-Lift Vehicle: Performance, Cost, and Schedule Projections for the First of the Scorpius™ Low-Cost Launch Vehicles

Scorpius™ is a Microcosm program, under two Phase III Small Business Innovation Research contracts at the Air Force Research Laboratory, Space Vehicles Directorate. The Scorpius™ program is to develop an entirely new launch vehicle family with the objective of reducing total launch cost by a factor of 5 to 10. This paper reports on status and substantial progress of the program since our last USU update. Specifically, the Sprite Mini-Lift Vehicle is projected to have a first DT &E tlight in the first quarter of 200 I and first production flight in the first quarter of 2002. It has a planned payload capability of 440 Ih. to low Earth orbit (due east launch). Total cost to orbit of the system is projected at $2 million (FY99$) after 10 launches. System development has focused initially on smaller suborbital and orbital vehicles, although system level design has been done for vehicles ranging from a small, single engine suhorbital, the SR-S, to massive heavy lift vehicles capable of putting 160,000 lb. into low-Earth orbit. The first test vehicle, the SR-S suborbital, was successfully launched at White Sands Missile Range on Jan. 27, 1999 and a larger single stage suborbital is scheduled for launch in late 1999

Changing the Paradigm of Space Testing: The F.A.S.T. Program

The high cost of access to space is driven in part by a cost spiral -- higher costs lead to fewer missions which leads to a demand for higher reliability which leads to higher costs. One way to potentially break this cycle is to introduce the opportunity for rapid, low-cost experiments leading to a larger number of near term experiments which, in turn, should result in higher performance, greater reliability, and lower cost systems which will spur the demand for additional rapid, low-cost experiments. A program has been initiated to help bring this about, initially with suborbital flights and subsequently with orbital flights of small experiments and instruments. The first FAST experiment was flown on board a Scorpius SR-XM suborbital vehicle launched from White Sands Missile Range on March 9, 2001

Preliminary space mission design under uncertainty

This paper proposes a way to model uncertainties and to introduce them explicitly in the design process of a preliminary space mission. Traditionally, a system margin approach is used in order to take the min to account. In this paper, Evidence Theory is proposed to crystallise the inherent uncertainties. The design process is then formulated as an optimisation under uncertainties(OUU). Three techniques are proposed to solve the OUU problem: (a) an evolutionary multi-objective approach, (b) a step technique consisting of maximising the belief for different levels of performance, and (c) a clustering method that firstly identifies feasible regions.The three methods are applied to the Bepi Colombo mission and their effectiveness at solving the OUU problem are compared

Displaced geostationary orbits using hybrid low-thrust propulsion

In this paper, displaced geostationary orbits using hybrid low-thrust propulsion, a complementary combination of Solar Electric Propulsion (SEP) and solar sailing, are investigated to increase the capacity of the geostationary ring that is starting to become congested. The SEP propellant consumption is minimized in order to maximize the mission lifetime by deriving semi-analytical formulae for the optimal steering laws for the SEP and solar sail accelerations. By considering the spacecraft mass budget, the performance is also expressed in terms of payload mass capacity. The analyses are performed both for the use of pure SEP and hybrid low-thrust propulsion to allow for a comparison. It is found that hybrid low-thrust control outperforms the pure SEP case both in terms of payload mass capacity and mission lifetime for all displacements considered. Hybrid low-thrust propulsion enables payloads of 255 to 487 kg to be maintained in a 35 km displaced orbit for 10 to 15 years. Adding the influence of the J2 and J22 terms of the Earth’s gravity field has a small effect on this lifetime, which becomes almost negligible for small values of the sail lightness number. Finally, two SEP transfers that allow for an improvement in the performance of hybrid low-thrust control are optimized for the propellant consumption by solving the accompanying optimal control problem using a direct pseudospectral method. The first type of transfer enables a transit between orbits displaced above and below the equatorial plane, while the second type of transfer enables customized service for which a spacecraft is transferred to a Keplerian parking orbit when geostationary coverage is not needed. While the latter requires a modest propellant budget, the first type of transfer comes at the cost of an almost negligible SEP propellant consumption

Flight Operations Analysis Tool

Flight Operations Analysis Tool (FLOAT) is a computer program that partly automates the process of assessing the benefits of planning spacecraft missions to incorporate various combinations of launch vehicles and payloads. Designed primarily for use by an experienced systems engineer, FLOAT makes it possible to perform a preliminary analysis of trade-offs and costs of a proposed mission in days, whereas previously, such an analysis typically lasted months. FLOAT surveys a variety of prior missions by querying data from authoritative NASA sources pertaining to 20 to 30 mission and interface parameters that define space missions. FLOAT provides automated, flexible means for comparing the parameters to determine compatibility or the lack thereof among payloads, spacecraft, and launch vehicles, and for displaying the results of such comparisons. Sparseness, typical of the data available for analysis, does not confound this software. FLOAT effects an iterative process that identifies modifications of parameters that could render compatible an otherwise incompatible mission set