ASTRO EXAM 1 CONCISE

Name five different types of space missions and give one example of each type.

Navigation (GPS), Communications (Starlink), Scientific Exploration (Mars rovers), Remote Sensing (Weather satellites), Human Exploration/Settlement (Lunar landings).

Explain several ways that space is advantageous for certain tasks compared to doing the same tasks on Earth.

Space offers positional (global coverage), line-of-sight (clear views), environmental (vacuum, microgravity), and place advantages (access to other planets).

What are the two main parts that make up a complete spacecraft?

The **Payload** and the **Spacecraft Bus (S/C Bus)**.

What does a mission objective tell us about a space mission?

It defines **WHAT** will be accomplished, stating the clear, specific mission goal.

Which part of a space mission actually does the main job of the mission?

The **Payload** directly accomplishes the mission objective.

How much was the global space economy worth in 2019, and how much did it cost to launch one kilogram to Low Earth Orbit in 2015?

The global space economy was worth **$430 billion** (in Fall 2025 context). It cost approximately **$10,000 per kilogram** to launch to LEO in 2015.

Name three main jobs that ground systems do for space mission operations.

Ground systems provide **Earth antennas for communication**, **mission control**, and **data processing**.

What is the basic rule that explains what does the mission objective and what parts help it?

**Payload-Centric Mission Design**: the payload achieves the mission, and all other elements support it.

List the six major environmental factors that affect spacecraft in Earth orbit.

**Gravity, Atmosphere, Vacuum, Charged Particles, Electromagnetic Radiation, and Micrometeoroids/Debris**.

Define what an Astronomical Unit (AU) is and state how long it takes light to travel from the Sun to Earth.

**1 AU** is ~150 million km. Light takes approximately **8 minutes** to travel from the Sun to Earth.

Define spacecraft survivability and explain why it is important for mission success.

**Survivability** is the ability to perform its intended function after environmental stress. It's critical because the payload must survive to achieve objectives.

Name the nuclear process that creates energy in the Sun and identify the two main types of radiation the Sun emits toward Earth.

**Hydrogen fusion to helium**. The Sun emits **electromagnetic radiation** and **charged particles** (Solar Wind).

State the approximate altitude ranges for Low Earth Orbit (LEO) and Geostationary Earth Orbit (GEO).

LEO: **160 km to 2000 km**. GEO: **35,786 km**.

List three specific design responses that spacecraft engineers use to protect spacecraft from environmental factors.

**Shielding** (radiation), **thermal control systems** (temperature), and **material selection** (vacuum, atomic oxygen).

Define outgassing and explain why it occurs in the vacuum of space.

**Outgassing** is when materials release gases as pressure drops in space's extremely low-pressure vacuum.

Define what an orbital period is and explain whether spacecraft in LEO or GEO have longer orbital periods.

An **orbital period** is the time for one orbit. **GEO** spacecraft have longer periods due to their much higher altitude/radius.

List the five main phases of the aerospace design life cycle in order.

1. **Concept Exploration**, 2. **Detailed Development**, 3. **Production and Launch**, 4. **Operations and Support**, 5. **End of Life**.

What is the main purpose of the Systems V approach in spacecraft development?

To ensure systems **meet requirements (verification)** and **accomplish mission objectives (validation)** by managing complexity through decomposition and integration testing.

Name the seven major subsystems that make up a spacecraft bus.

**Structures, Electrical Power System (EPS), Attitude Determination and Control (ADC), Propulsion, Thermal Control, Communications, and Command and Data Handling (CDH)**.

Define what a payload is and explain why it drives all other spacecraft design decisions.

A **payload** does the mission objective. It drives design decisions because all other spacecraft elements support its function.

State the primary functions of the spacecraft structures subsystem.

Provides **strength** (launch survival), **stiffness** (vibration control), **support** for components, **protection**, and **deployment mechanisms**, while minimizing mass.

List the main components of a spacecraft electrical power subsystem.

**Power generation** (e.g., solar panels), **energy storage** (e.g., batteries), and **power distribution and conversion electronics**.

Define Technology Readiness Level (TRL) and state the TRL number for flight-proven technology.

**TRL** is a 9-level scale measuring technology maturity. **TRL 9** is flight-proven technology.

Name two major design reviews that occur during spacecraft development and state their purpose.

**System Requirements Review (SRR)**: ensures all system needs meet mission objectives. **Preliminary Design Review (PDR)**: evaluates preliminary design feasibility.

Define Concept of Operations (ConOps) and state its primary purpose in space mission development.

**ConOps** illustrates mission activities and stakeholder interactions. Its primary purpose is **stakeholder communication and requirements validation**.

List the four critical pieces of mission information that drive spacecraft design decisions.

**Destination/orbit, mission objectives, mission duration, and reliability requirements**.

State why payload characteristics must drive spacecraft bus design rather than using standard configurations.

Each mission has unique requirements. Custom design optimizes performance, avoiding over/under-designed systems.

Define spacecraft configuration and list three factors that influence configuration decisions.

**Configuration** is the overall physical arrangement of subsystems. Factors: **mission requirements, launch constraints, and thermal management**.

Name the primary functions of spacecraft fixed structures during launch and on-orbit operations.

Provides **strength** for launch survival, **stiffness** for vibration control, **supports** components, **protects** electronics, and provides **thermal** interfaces/shielding.

List four types of deployment mechanisms used in spacecraft systems.

**Gimbals, springs, motors, hinges, pyrotechnics**.

Identify the difference between structural strength and stiffness requirements in spacecraft design.

**Strength** prevents breaking/deformation under load. **Stiffness** controls natural frequency/vibration to avoid resonance.

Define pyrotechnic devices and state why they are used for spacecraft deployment events.

**Pyrotechnic devices** are explosive mechanisms for reliable, one-time deployment. Used for high-force actuation and launch vibration immunity.

List the four main functions of a spacecraft electrical power subsystem (EPS).

To **generate, store, condition, and distribute** electrical power.

State three unique challenges of providing power to spacecraft compared to Earth-based systems.

No convenient power sources in space, inability to refuel/replace components, and power requirements vary dramatically across mission phases.

Define spacecraft attitude and explain why it should not be confused with altitude.

**Attitude** is orientation in space; **altitude** is height above Earth. They are distinct concepts of orientation vs. position.

Name four environmental disturbances that affect spacecraft attitude in Earth orbit.

**Gravity gradient torques, solar radiation pressure, magnetic field interactions, and atmospheric drag** (in LEO).

List three reasons why spacecraft need precise attitude control.

For **payload pointing**, **solar array orientation**, and **antenna pointing**.

Define functional block diagrams and state their primary purpose in spacecraft systems engineering.

**FBDs** document system-level interfaces. Their primary purpose is to analyze system complexity and integration requirements.

Define battery capacity, C-rate, and depth of discharge for spacecraft power systems.

**Capacity** (W·hr) is total energy storage. **C-rate** is discharge speed (e.g., C=1 for 1 hour). **Depth of Discharge (DoD)** is usable capacity percentage.

List the three types of interfaces shown in spacecraft functional block diagrams and their standard color coding.

**Power (red lines), Data (blue lines), and Mechanical (black lines)**.

List the three primary communication paths used in spacecraft operations and define each one.

**Uplink** (ground to S/C commands), **Downlink** (S/C to ground data), **Crosslink** (S/C to S/C data/coordination).

State which frequency band is commonly used for GPS satellites and identify the primary reason this band was selected for navigation applications.

**L-band (1-2 GHz)**. Primary reason: **good ionosphere penetration**.

Define command and data handling (CDH) subsystem and name the four primary functions it performs for spacecraft operations.

**CDH** is the central computer system. Functions: **command processing, data management, spacecraft control, and subsystem coordination**.

Identify the three main types of commands that CDH systems process and state the primary difference between real-time commands and stored command sequences.

**Real-time, stored command sequences, emergency safing**. Real-time execute immediately; stored execute at scheduled times/conditions.

Define thermal control subsystem and state why maintaining component temperatures within operating ranges is critical for spacecraft mission success.

**Thermal control** maintains component temperatures. Critical because out-of-range temperatures cause failures, material cracking, and performance degradation.

Name three passive thermal control techniques and identify which technique is most commonly used to insulate spacecraft from the space environment.

**Surface coatings, multi-layer insulation (MLI), radiators**. **MLI** is most common for insulation.

List three spacecraft subsystems that must interface directly with the communications system and state one specific interface requirement for each.

**EPS**: provides power; **ADC**: provides antenna pointing; **CDH**: manages data formatting/transmission.

State the temperature range that spacecraft can experience in LEO and identify why convective heat transfer is not available in space.

LEO temperatures: **-150°C to +150°C**. Convective heat transfer is unavailable due to **no atmosphere**.