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October 23, 2014

Homework Help: Physics-VASTS

Posted by red on Thursday, March 7, 2013 at 4:29pm.

The Mass Budget: Mars Reconnaissance Orbiter Repair Mission

Operational Concept Math

Problem: The Mars Reconnaissance Orbiter (MRO) has encountered a failure in its High Resolution Imaging Science Experiment (HiRISE) camera.



Mission Case:

As the HiRISE camera contains the largest reflecting telescope ever carried on a deep space mission, NASA does not want to lose their investment only 6 years into its operational deployment. Using the recent success of the Satellite Servicing Capabilities Office as a model, NASA has been decided that a robotic mission will be sent into Mars orbit to intercept and repair the camera. It is your responsibility to determine the mass of each of the three space craft stages (see below for instructions) and then present the appropriate Mission Scope information and Operational Concept (“ConOps”) data in spreadsheet format. The presentation of Mission Scope and of “ConOps” is a key link in communicating the engineering and mission design decisions to policy makers and administrators; therefore, all NASA engineers must be practiced in the creation of these documents.

Objectives for MRORM:

To fully grasp the writing aspect of this assignment, you should review the following presentation on Mission Scope (including key definitions!) and ConOps. This PDF slideshow will give you the information and examples necessary to write your Mission Scope and ConOps.

The pre-formatted spreadsheet file is available here. A Google Docs link for this spreadsheet will be provided at the bottom of this document. Your assignment will be graded on the accuracy of your calculations using the spreadsheet, as well as on the efficiency and clarity of your mission scope statements. Each area of mission scope (Need, Assumptions, Constraints, and Drivers) should be answered in a sentence.

Operational Details

The mission to repair the MRO will be on the new Space Launch System spacecraft. This system is composed of three distinct elements:

1. SLS Core Stage – Used for liftoff from Earth’s surface and insertion into Low Earth Orbit (LEO)

a. Math Requirement: Determine the mass of the SLS Core Stage Elements.

2. Earth Departure Stage (EDS) – Used for transfer from LEO to Low Mars Orbit (LMO)

a. Math Requirement: Determine the mass of the Earth Departure Stage Elements.

3. Orion Stage – Used to transport crew and supplies

a. The “crew” travels in the MultiPupose Crew Vehicle (MPCV) for this mission will be four (4) “Robonaut 2” robots.

i. Two Robonauts will be inside the MPCV, Two Robonauts will be outside.

ii. The Robonauts will be denoted as R2D1, R2D2, R2D3, and R2D4.

iii. The mass of the Robonauts and their supplies for fixing MRO is 1000kg.

b. Other Orion Elements include the Orion Service Module and Thruster Fuel

c. Math Requirement: Determine the total mass of all Orion elements

i. Mass of the only the MPCV capsule and robots is 9913kg.

Senior NASA Operations Directorate engineers have worked out the following phases, and have determined mass loss factor for each phase. You will need to work backwards through the each operational phase to determine how much mass the space craft must have to begin each phase, ultimately leading you to determine the original mass the space craft must start with when it launches from Earth.

Operational Phase 1 (Earth Surface -> LEO)

· Spacecraft launches from Kennedy Space Center.

· Initial Spacecraft Elements Present:

o SLS Core Stage

o Earth Departure Stage

o Orion Stage

· The SLS Core stage is jettisoned after reaching LEO

· The mass loss factor for this phase is 0.1758

o This indicates that the initial mass, multiplied by this factor, will give you the final mass for the phase.

Operational Phase 2 (LEO ->LMO)

· Spacecraft increases orbital speed with Earth Departure Stage engines and arrives at LMO

· Initial Spacecraft Elements Present:

o Earth Departure Stage

o Orion Stage

· There is a significant amount of fuel spent in changing velocity in this phase.

· No spacecraft elements are jettisoned in this phase.

· The mass loss factor for this phase is 0.5747

Operational Phase 3 (R2 Units repair MRO)

· Spacecraft intercepts MRO while in LMO, R2 units do repair work on HiRISE camera.

· Initial Spacecraft Elements Present:

o Earth Departure Stage

o Orion Stage

· The Earth Departure Stage is jettisoned as the spacecraft meets with the MRO.

· The mass loss factor for this phase is 0.1257

Operational Phase 4 (LMO -> LEO)

· Spacecraft returns from LMO to LEO

· There is a significant amount of fuel spent in changing velocity in this phase

· No spacecraft elements are jettisoned in this phase.

· The mass loss factor for this phase is 0.7378

Operational Phase 5 (LEO ->Earth Surface)

· Spacecraft performs a de-orbit burn and aerobraking maneuvers to return to the surface of Earth.

· The Orion Service Module is jettisoned in this phase.

· The Orion MCPV (8913kg) and Robonauts (1000kg) are the only remaining spacecraft elements.

· The mass loss factor for this phase is 0.4455

Operations Overview (All Phases)

· The mass of Capsule and Robots returned to Earth is 9913kg

· The combined mass factor from initial takeoff mass to returned mass is 0.004174281

o This indicates that the initial takeoff mass, multiplied by the factor above, would equal the mass of the Capsule and Robonauts returned to Earth’s surface.

Assignment Specifics:

1. Download the Excel spreadsheet for this assignment here. If needed, use the Google Docs version of the spreadsheet located here (remember to save this file into your personal Google Docs account first!). Red fonts in this section correspond with red fonts in the spreadsheet, indicating graded items.

2. Using the mass loss factors provided above, calculate the massinitial and massfinal for each Operational Phase. HINT: Mass loss factors work via multiplication if you know massinitial, but they can also work via division if you know massfinal!

3. Calculate the total mass of each stage listed below and input these values into their labeled areas of the spreadsheet.

a. SLS Core Stage elements

i. Hint: this is Phase 1’s massinitial – Phase 1's massfinal

b. Earth Departure Stage (EDS) elements

i. Hint: This is Phase 2’s massinitial – Phase 3’s massfinal

c. Orion MCPV Stage elements

i. This is Phase 4’s massinitial – 1000kg (the mass of the Robonauts)

4. Write a very brief description of the following Mission Scope elements (for this mission) in the given area of the spreadsheet. See the provided presentation on Mission scope for help on these definitions. Give one sentence each.

a. Need

b. Assumptions

c. Constraints

d. Drivers

5. It will be in your long term best interest (especially for the VASTS Summer Academy) to use Excel’s abilities to write formulas and algorithms to calculate results instead of doing each of these calculations with a calculator. Please see some of the suggested walkthroughs for these formulas linked on the course site.

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