Ascent Vehicle Research Articles

QnAs with John P. Grotzinger

QnAs with John P. Grotzinger

Feasibility of a single port Hybrid Propulsion system for a Mars Ascent Vehicle

Developments in hybrid propellants over the last decade make the hybrid motor a viable candidate and possibly an enabling technology for a Mars Ascent Vehicle (MAV) as part of a Mars Sample Return (MSR) campaign. Fast regression rate fuels such as paraffin allow for single port hybrid designs that overcome the disadvantages associated with classical hybrid fuels. Additionally, paraffin has a both a weak and low glass transition temperature, making it an ideal candidate for a Mars application. Nytrox, a high performance oxidizer made of a mixture of nitrous oxide and oxygen, can be chosen to match the temperatures on Mars. The hybrid MAV can survive the harsh Martian environment with minimal or no thermal conditioning and it can meet the design challenges posed by coordinating with the other aspects of MSR.

Optimal Guidance for Quasi-planar Lunar Ascent

The minimum-time controls (thrust pitch angle and thrust yaw angle) for the three-dimensional transfer of a constant-thrust rocket from one state to another over a flat moon are used to develop guidance laws for operation over a spherical moon. The objective is to evaluate the effect of making approximations on the size of the thrust pitch angle on the suitability of the resulting control law as a guidance law. After assuming small out-of-plane motion (small yaw angle), three pitch angle control laws (exact, first-order, and zeroth-order) are developed. The three laws are employed in the sample and hold guidance of a lunar ascent vehicle. All three laws satisfy the final conditions and give essentially the same pitch and yaw control histories. Since the zeroth-order law can be obtained completely analytically (no iteration processes), it merits consideration for ascent guidance.

Control of a Magnetic Capture Device for Autonomous In-orbit Rendezvous

AbstractMission concepts proposed to return Mars soil samples to Earth involve a critical rendezvous phase with a passive sample container placed in Mars orbit by an ascent vehicle. An innovative magnetic capture device was recently proposed to increase the reliability and simplify capture operations. The present paper presents control aspects of this device. More specifically, the magnetic capture devices allows to damp rotation rates and to enforce a specific relative orientation of the sample container at a range of about 4 meters. The final contact is secured thanks to a additional, small, passive magnet. The linear stability and performance of the controller is analyzed, and non-linear simulations are presented.

Optimization of the Mars Ascent Vehicle for Human Space Exploration

Covers advancements in spacecraft and tactical and strategic missile systems, including subsystem design and application, mission design and analysis, materials and structures, developments in space sciences, space processing and manufacturing, space operations, and applications of space technologies to other fields.

Metal-CO2 Propulsion for Mars Missions: Current Status and Opportunities

*† Metal-CO2 propulsion is less known than other Mars in-situ resource utilization (ISRU) technologies. This concept, based on using Martian carbon dioxide as an oxidizer in jet or rocket engines, offers the advantage of no chemical processing for CO2 and thus requires less power consumption than ISRU alternatives. In this paper, we review various aspects of metal-CO2 propulsion, such as combustion of magnesium and aluminum in CO2, engine types and characteristics, production of liquid CO2 and metal fuel on Mars, and potential missions. Lunar and terrestrial applications are also discussed. I. Introduction N-SITU Resource Utilization (ISRU) is recognized as an enabling technology for exploration of Mars, which can significantly reduce the mass, cost, and risk of robotic and human missions. The critical element in future missions is the large mass of propellant for a Mars ascent vehicle, while power and propellant to accommodate a long stay and mobility on Mars are also important. Transportation of propellant from Earth to Mars requires tremendous increase in the initial mass of hardware in low Earth orbit (and hence mission cost) as compared to prior no-return missions. Fortunately, Mars possesses resources that can be used for propellant production. The Martian atmosphere consisting of 95% CO2 is the obvious and most promising in-situ resource. I

Venus sample return missions—a range of science, a range of costs

Venus sample return missions have been studied occasionally for the last 40 years, but only recently has technology advanced to the point where this kind of mission has been realistic. At the same time, however, cost constraints have become more important. NASA recently has been studying a set of Venus sample return missions which span a range of scientific goals and which have a corresponding range of costs. The simplest sample return from Venus is to fly through the upper atmosphere and return some of the gas to Earth. This turns out to be possible using a free-return ballistic trajectory. The gas sample would be captured at hypersonic velocities and would be greatly affected by the process, but we could still determine isotopic ratios to very high precision on the ground and may be able to determine elemental ratios. This mission is roughly a moderate Discovery class mission reminiscent of Stardust. The next level of sample return mission would be another atmosphere sample mission, but would involve much more benign sampling conditions. At Venus arrival the spacecraft would be aerocaptured into orbit at Venus and aerobrake to a circular orbit. A sample-gathering vehicle would enter the atmosphere and slow significantly, allowing capture of a well-mixed atmosphere sample which preserves chemical composition. An on-board rocket would then return the sample to Venus orbit, where the orbiting spacecraft would retrieve it and bring it back to Earth. This mission is somewhat beyond Discovery class, though not outrageously so. The most difficult level of sample return mission would be a sample from the surface of Venus. The surface of Venus is the hottest surface and has the greatest atmospheric pressure and density of any known surface in the solar system. This presents great challenges to both the sampling lander and to the Venus ascent vehicle (VAV) which must return the sample to orbit. Indeed, it is impossible in any practical sense to use a rocket ascent vehicle directly from the surface; instead; a balloon is used to lift the VAV with the sample to an altitude above the clouds where both temperature and pressure are not unlike Earth's, whence the rocket fires to orbit the sample. This mission is substantially more difficult and costly than the atmosphere sampling missions described above, but would allow direct examination of Venus to answer questions about solar system formation and Venus's evolution since then.

Regenerative Solid Oxide Fuel Cells for Mars Exploration

A regenerative solid oxide fuel cell was designed, built, and tested for Mars exploration. The fuel cell operates at night on CO and excess O2 generated from the Mars atmospheric C02 during the day. The primary objective of the device was to generate O2 from the Mars atmosphere for use as ascent vehicle propellant. The cells tested were composed of a 8-mole percent yttria stabilized zirconia (YSZ) electrolyte and 2 platinum electrodes. The fuel cell was tested by connecting it to an external circuit with adjustable resistance and then measuring cell voltage and current for different load points. The results obtained were consistent with the theoretical relations predicted by thermodynamics and electrochemistry. The performance loss of the fuel cell, observed during the first 40 hours of operation in the fuel cell mode, was attributed to chemisorbtion of CO in the platinum electrodes. It was found that the concentration overpotential was negligible and the calculated activation overpotential fit well with the Tafel equation. The results suggest that operating O2 generator cells as fuel cells with low fuel utilization at night has distinct advantages for Mars missions.

Rover trials for Mars sample return Mission prove successful

During the Mars Sample Return mission the Athena Rover will acquire remote sensing andin‐situ measurements of surface materials, drill into rocks and collect cores, acquire soil samples, and place the rock and soil samples in an ascent vehicle on the lander. After the ascent vehicle and its sample cache are launched, the rover will conduct an extended mission focused on exploration and discovery. The Field Integrated Design and Operations (FIDO) Rover simulates these sampling and exploration activities with a science payload similar to the Athena Rovers. In its initial field trials, FIDO was deployed and controlled remotely for 2 weeks in the Silver Lake area of the Mojave Desert in California. FIDO successfully completed traverses of over 500 m in diverse terrains while acquiring imaging and spectral reflectance data. FIDO also successfully identified, maneuvered to, and cored into rocks. The trials validate the mission operations approach andprovide many lessons that will maximize the science return associated with rover‐based observations and sampling activities.

Design trade space for a Mars ascent vehicle for a Mars sample return mission

The design of an ascent vehicle for Mars sample return is one of the most challenging problems to be addressed for this type of mission. This paper identifies the spectrum of performance requirements that could be required of a Mars ascent vehicle for a sample return mission. With this understanding of performance requirements, an investigation of technology requirements is presented. These technology requirements are compared to past and existing technology in order to identify which are the lagging technologies and where development investment should be made. Mars ascent approaches which include storable propellants and in-situ production of propellants are considered. Several technology comparisons are performed to illustrate performance regions that are appropriate for different technologies. Several promising propulsion technologies are identified: miniature constant displacement pumps, bladder lined composite tankage, thin wall metal tankage and advanced propellants. Technologies that have been designed, built, tested and flown are emphasized.

A MODEL COMPARISON FOR OPTIMAL MARS ASCENT TRAJECTORIES

Maximum payload Mars launch trajectories are computed for a nominal two-stage Mars ascent vehicle. This vehicle transfers a payload from the surface of Mars to a circular parking orbit about Mars in preparation for transferring the payload to an Earth return vehicle. Both gravity turn and pitch-rate control models for controlling the ascent vehicle's trajectory are investigated. For each case, a rather complicated nonlinear programming problem is obtained and then solved using a sequential quadratic programming algorithm.

A New Trajectory Optimisation Tool (ALTOS) Applied to Conventional Launchers

ALTOS is a newly developed Advanced Launcher Trajectory Optimisation Software. This new tool can be characterised by its three main features: Modelisation of the ascent vehicle, of the ascent trajectory and of constraints, 3DoF ascent trajectory simulation, 3 DoF ascent trajectory optimisation based on the direct collocation and direct multiple shooting method. In this present paper, the results obtained with ALTOS for conventional launchers such as Ariane 5 are presented together with the experience gained during the study of the operation and the performance characteristics of the tool.

Flight Control Frequency Response Testing of the Shuttle Ascent Vehicle

Flight Control Frequency Response Testing of the Shuttle Ascent Vehicle

Manufacture in space: the MINOS system

The manufacture in Space of products for use on Earth is a possibility for the 1990s. The MINOS project is based on the idea of a free-flyer station for the current medium-level production of either unique products (which cannot be made on Earth), or of economic yields of products which cannot be obtained in sufficient quantities on Earth. At present, only the main system may be defined from general specifications: electrical power (10 kW), residual acceleration (10 −5 g), processing cycle duration (10 hr). The launch vehicle is Ariane I and its improved versions (models II, III and IV). The outer structure of the spececraft is described with solar panels, energy storage (battery and inertial storage) and control systems. The definition of orbital parameters capable of accommodating the basis specifications, especially the high energy level and the re-entry conditions on the Guiana base, is a major problem. The re-entry vehicle is studied from a pure ballistic trajectory point of view. From the results of orbital performance, the mass of the spacecraft and also the mass of the ascent vehicle are evaluated. For this latter value, its determination is directly related to the cost of space-processed materials. A general overview is given of the other spacecraft sub-systems such as satellite tracking, communications, ground stations, resources requirements, telemetry, onboard computing system etc.

Feasibility of rocket propellant production on Mars

In situ production of rocket propellant to reduce landed mass requirements for Mars return missions has been investigated. The analysis has shown that a system which utilizes atmospheric carbon dioxide and soil moisture to produce liquid methane-oxygen propellant requires a landed mass which is less than half the mass of the ascent vehicle it produces.

A guidance system for the ascent of a martian probe

A radio command guidance system is described which is useful for guiding a probe from the surface of Mars to rendezvous with a mission module flying by Mars on an escape trajectory. Lightness and simplicity are the design goals. The system includes, in the ascent vehicle, a radar transponder, a three axis gyroscope dependent autopilot and a three channel radio command system. In the larger mission module, there is a radar, a computer for navigation and guidance calculations, and a command transmitter. The paper describes the system and shows the effect of various errors on the total fuel required.

A Guidance System for the Ascent of a Martian Probe

A radio command guidance system is described which is useful for guiding a probe from the surface of Mars to rendezvous with another vehicle flying by Mars on an escape trajectory. Lightness and simplicity are the design goals. The system includes, in the ascent vehicle, a radar transponder, three axis gyroscope dependent autopilot and a three channel radio command system. In the larger flyby vehicle, there is a radar, a computer for navigation and guidance calculations, and a command transmitter. The paper describes the system and shows the effect of various errors on the total fuel required.