ASTR1003 Space Practice questions

Q3: What is a Low Earth Orbit (LEO), and why is it a common choice for spacecraft?

– Orbit between 200–2000 km altitude.

– Common due to proximity, low latency, and strong signals.

– Useful for observation and communication; ISS orbits in LEO.

Q4: Why are geostationary orbits advantageous for communication and weather satellites?

– Satellite appears stationary from Earth—ideal for fixed antennas.

– Enables constant observation of large Earth regions.

Q5: In space travel, what is more crucial than distance, and why?

– ΔV (change in velocity) is more important than distance.

– Determines fuel needs and success of rendezvous.

Q6: How does a Hohmann Transfer Orbit work, and why is it considered the minimum energy orbit for traveling between planets like Earth and Mars? 

– Uses elliptical orbit and timed engine burns to transfer between orbits.

– Requires minimal energy—ideal for interplanetary missions.

Q8: What does the Rocket Equation express, and why is the exponential nature of the equation significant for rocket design? 

– Links velocity change to mass ratio and exhaust velocity.

– Small ΔV changes drastically affect fuel needs.

Q9: Why are rocket stages essential in space launch vehicles, and how do they contribute to overcoming the challenges posed by the Rocket Equation? 

– Improve efficiency by shedding mass after fuel burn.

– Helps manage the Rocket Equation’s limitations.

Q10: What is aerobraking, and how does it help spacecraft save energy in space travel? 

– Uses atmospheric drag to slow down without fuel.

– Saves mass; useful on Earth, Mars.

Q11: What is a gravity assist, and how does it enable spacecraft to achieve significant changes in velocity without requiring excessive fuel? 

– Spacecraft uses a planet’s motion and gravity to gain speed.

– Reduces fuel needs for major velocity changes.

Q12: In space engineering, why is the rocket equation important, and what does it emphasize about the mass ratio in rockets? 

– Shows how fuel mass dominates rocket design.

– Highlights need for high exhaust velocity and efficient staging.

Q13: What are the advantages and disadvantages of using liquid hydrogen/liquid oxygen versus a hydrocarbon (such as RP-1) with liquid oxygen as propellants in space rockets? 

– LH₂/LOX: higher exhaust velocity, but low density and cryogenic issues.

– RP-1/LOX: higher density and easier handling, but lower performance.

Q14: What is the primary disadvantage of solid-fuel rockets compared to liquid-fuel rockets? 

– Cannot be throttled, stopped, or restarted once ignited.

Q15: What is a hypergolic fuel, and why are these fuels advantageous for certain space missions? 

– Ignites on contact with oxidizer—no ignition system needed.

– Useful for reliable and restartable space operations.

Q16: What are the challenges associated with rocket turbopumps, and why are they considered one of the most difficult parts of a rocket to get right? 

– Must be small, light, and move fluids at high pressures.

– Prone to leaks, cavitation, and thermal stress.

Q17: What is the purpose of the De Laval nozzle in a rocket engine's combustion chamber? 

– Accelerates exhaust gases from subsonic to supersonic speeds.

– Maximizes thrust efficiency.

Q18: What recent changes have impacted the space launch market?

– SpaceX’s low-cost, reusable rockets have increased competition and access.

Q20: What was the initial purpose of the US human space program, and how did it change over time? 

– Initially to beat USSR (Apollo).

– Later focused on maintaining space presence (Shuttle, ISS).

Q21: What are the key factors contributing to the cost-effectiveness of SpaceX rockets 

– Reusability, fast iteration, low-cost design, small teams, and Musk’s leadership.

Q22: According to Elon Musk, how does SpaceX plan to further reduce the cost of getting into space in the near future? 

– Starship’s rapid reusability and simplified, mass-producible design.

Q23: What is a key limitation of ion drives that makes them unsuitable for lifting spacecraft into orbit from the surface of a planet? 

– Produce very low thrust—only useful in space, not for launch.

Q24: What is the basic idea behind a nuclear-thermal rocket, and what advantage does it offer compared to chemically fuelled rockets? 

– Heats hydrogen via a nuclear reactor for high exhaust velocity.

– More efficient and lighter than chemical rockets.

Q25: What is one benefit of launching rockets from aircraft, and which companies have used or proposed this method? 

– Uses jet engines to reach high altitudes before rocket ignition.

– Reduces launch costs; used by Virgin Orbit and Galactic.

Q26: What is the basic idea behind a space elevator, and what is the fundamental problem associated with its construction? 

– A cable from geostationary orbit to Earth for cargo transport.

– No material strong/light enough exists yet; carbon nanotubes are promising.

Q27: What are the contrasting conclusions drawn regarding ownership and jurisdiction in the sea and airspace? 

– Sea: international waters, no national ownership.

– Airspace: controlled by the country beneath it.

Q28: Discuss the potential challenges if countries were to claim ownership of the space above their territories. 

– Satellites in LEO pass over many countries quickly.

– Would require permission from each, hindering space use.

Q29: What are the main provisions of the 1967 Outer Space Treaty? 

– No nukes in space.

– Space open to all nations.

– Developed for benefit of all.

– No ownership of celestial bodies.

– Launching countries are responsible.

– Astronauts must be rescued and returned.

Q30:Explain how space laws are normally enforced, and some of the problems that might arise. 

– Enforced through national laws.

– Multi-nation cases cause disputes.

– Fault and liability can be hard to determine.

Q31: What is one example of a space incident involving multiple countries and the challenges in enforcing space law? 

– 2009 collision: US and Russian satellites.

– Highlighted complexities in liability and international enforcement.

Q32: What are 3 flaws in the Outer Space Treaty?

– No clear boundary of “space.”

– Unclear spacecraft registration rules.

– Doesn’t address private company roles.

Q33: What are some legal issues to consider when launching a satellite into space? 

– Launch permits, export laws, spectrum allocation.

– Liability insurance and collision avoidance regulations.

Q34: What is the current estimated size of the global space economy, and what is a significant factor contributing to its growth? 

– ~$500 billion/year.

– SpaceX’s low-cost launches are a major growth factor.

Q35: How does the space economy differ from the economy of a country on Earth, and what dominates the commercial space economy? 

– Entirely Earth-focused: services delivered back to Earth.

– Dominated by communications (e.g., satellite TV).

Q36: In the government space economy, what sector dominates government space expenditure? 

– Military expenditure is the largest component.

Q37: What are the two main reasons contributing to the rapid growth and transformation of the space industry? 

– Cheaper launches (e.g., SpaceX).

– Smaller, more capable satellites.

Q38: How have improvements in electronics and computing contributed to the increase in small satellite launches?

– Miniaturization allows high function in small form.

– Cheaper and based on phone tech.

Q39: What was the original purpose of fixed satellite communications, and how did it work?

– International calls via geostationary satellites.

– Signal sent up from one station, down to another.

Q40: Why is satellite communication particularly valuable for military applications? 

– Enables wide-area communication with mobile assets.

– Works where traditional systems can’t.

Q41:Why is proper frequency allocation important for communication systems, and who manages it? 

– Prevents signal interference.

– Managed by national regulatory authorities.

Q42: How do dish antennas help mitigate frequency congestion in satellite communications? 

– Directional beams avoid interference.

– Narrow beamwidth allows satellite signal separation.

Q43: What challenges do geostationary orbits pose for communication satellites, and how do satellite constellations in low Earth orbit address these challenges? 

– GEO: expensive, high latency, faint signal.

– LEO: stronger signals, low latency, but need many satellites.

Q44: What are the advantages of using lasers for space communication, and what challenges do they present? 

– High data rates and directionality.

– Can’t pass through clouds; requires precise targeting.

Q45: How does the Global Positioning System (GPS) work, and what is the purpose of having multiple navigation satellites in intermediate orbits? 

– Triangulation of signals from at least 3 satellites.

– Intermediate orbit balances coverage, size, and cost.

Q46: What are the primary reasons for using satellite remote sensing, and how does it offer advantages over other forms of observation like flying drones or helicopters? 

– Wide, fast coverage and access to hostile/inaccessible areas.

– Useful for weather, military, and global observation.

Q47: How does resolution impact satellite remote sensing, and what factors influence the achievable resolution of satellite images? 

– Resolution depends on wavelength, orbit, and mirror size.

– Best (10 cm) from large optics in LEO.

Q48: Why is the area covered an important aspect of satellite remote sensing, and what factors influence the area covered by a satellite in each image? 

– Balance between detail and area.

– Depends on camera pixel count and sensor design.

Q49: Why is revisit time an important factor in satellite remote sensing, and how does it impact the usefulness of the collected data? 

– Determines how often a spot is observed.

– Critical for monitoring changes and real-time needs.

Q50: Why is the choice of wavelengths crucial in remote sensing, and how does it impact the information obtained about the Earth's surface? 

– Affects material identification and info quality.

– Used for thermal data, composition, vegetation, etc.

Q51: Why does Synthetic Aperture Radar (SAR) offer advantages over traditional radar imaging, and what challenges does it overcome? 

– Works at night and through clouds.

– Provides high-resolution images using orbital motion.

– Requires complex processing and covers smaller areas.

Q52: Why is it essential to design a spacecraft to withstand intense noise and vibration during launch, and how is this typically ensured? 

– Launch generates intense vibrations that can damage components.

– Tested using shaker tables to simulate launch conditions.

Q53: Explain the challenges posed by the vacuum of space on spacecraft materials and components, and how engineers address these challenges during spacecraft design. 

– Pressure differentials can damage sealed parts.

– Plastics may outgas, lubricants degrade, sunlight causes damage.

– Engineers use tested materials and solid lubricants.

Q54: Explain the challenges posed by radiation to spacecraft electronics and describe the measures engineers take to mitigate these challenges 

– Causes malfunctions or permanent damage.

– Mitigated with radiation-hardened chips, redundancy, and safe modes.

Q55: What are the primary challenges associated with using solar power for spacecraft, and how do space missions address these challenges? 

– Shadow periods limit power in orbit.

– Deep space has reduced sunlight.

– Batteries or RTGs used as backup.

Q56: Why is spacecraft orientation control crucial, and what are some methods used to achieve it? 

– Crucial for communication, solar power, and observations.

– Controlled using sensors, reaction wheels, and thrusters.

Q57: Why is temperature control crucial for spacecraft, and what methods are employed to regulate temperature in space? 

– Spacecraft can overheat or freeze due to radiation-only heat transfer.

– Uses foil, radiators, and sunshields to regulate temperature.

Q58: Why are satellites often expensive to build, and what challenges contribute to their high costs? 

– Custom designs, extensive testing, high reliability needs.

– Costly launches demand capable, reliable systems.

– Mass production (e.g., Starlink) is reducing costs.

Q59: What factors make a good launch site, and why is launching towards the East preferable for rockets? 

– Needs safety from populated areas and oceans nearby.

– Eastward launch benefits from Earth’s rotation (ΔV boost).

Q60: What factors influence the complexity of operating a spacecraft, and how does the operational complexity vary for different types of satellites? 

– Depends on type:

 • GEO satellites = low effort.

 • LEO constellations = complex tracking.

 • Astronomy satellites = intensive planning and calibration.

Q61: What is the primary purpose of NASA's Deep Space Communications Complex in Canberra? 

– Communicates with spacecraft >100,000 km away.

– Provides data relay and mission support.

Q62: How does the Deep Space Network manage communication with spacecraft, and what factors contribute to the complexity of scheduling communication sessions? 

– High demand from missions and limited antennas.

– Must consider critical events, maintenance, and conflicts.

Q63: Describe the density of tracked space junk per unit volume in space, and explain why this seemingly low density is still a significant concern. 

– ~1 piece per 10 million km³.

– High speeds make even small fragments hazardous.

Q64: Explain the factors contributing to the increase in space debris. 

– Rising launches (e.g., microsats, Starlink).

– Satellite collisions and deliberate destruction events.

Q65: What is the Kessler Syndrome, and what are the conditions that could lead to its occurrence in Earth's orbit? Additionally, mention a potential scenario where the Kessler Syndrome might be deliberately triggered. 

– Chain reaction of collisions in orbit.

– Can be triggered naturally or during space war.

Q66: How does the lifetime of space junk vary with altitude in low Earth orbit? Explain the relationship between altitude and the time it takes for a satellite's orbit to decay. 

– Lower altitudes = fast decay (200 km = 1 day).

– Higher = long-lived (900 km = 1000 years).

– Used strategically for planned reentry (e.g., Starlink).

Q67: How is space debris, particularly larger pieces (>10cm), tracked, and what methods are used for different sizes of debris? 

– >10cm: optical telescopes (e.g., SkyMapper).

– ~1cm: radar tracking.

– Tiny fragments: estimated from in-space impact tests.

Q68: How can the amount of space junk be reduced, and what challenges are associated with extending the lifetime of satellites through refuelling or repair? 

– Extend satellite life via refuelling/repair.

– Hard due to cost, aging parts, and orbital mismatch.

Q69: How can larger pieces of space debris, such as disused satellites, be potentially removed from orbit, and what challenges are associated with this approach? 

– Nets or drag devices like airbags can help deorbit.

– Issues: cost, legal responsibility, and weaponisation risk.

Q70: What are some of the legal challenges associated with managing space traffic, preventing collisions, and addressing liability issues in space, particularly in the context of satellite orbits? 

– No global space traffic control.

– Disputes over ownership, liability, and dual-use tech.

Q71: What are the most plausible targets for space mining, and why are they considered valuable? 

– M-type (metallic) asteroids.

– Contain valuable metals like nickel, iron, platinum.

Q72: Why is a metal asteroid such as 16 Psyche so valuable? 

– Huge mass = large total value.

– Iridium and platinum most valuable per kg.

Q73: What are the three key methods proposed to reduce the costs of asteroid mining? 

– In-space smelting.

– Targeting low-ΔV Near-Earth Objects.

– Using ion drives.

Q74: What is the envisioned transition from a colonial space economy to a true space economy, and why is asteroid mining considered crucial in this transition? 

– Start: extract resources for Earth.

– Goal: build self-sustaining space industry using in-situ materials.

Q75: What are the reasons advanced for sending people into space? 

– Survival of humanity.

– Inspiration and national pride.

Q76: What is the purpose of the space stations in low Earth orbit, and how does the Artemis program plan to utilize the SpaceX Starship in its Human Landing System (HLS) for lunar missions? 

– Stations support science and life support testing.

– Artemis uses Starship to land/retrieve astronauts on Moon.

Q77: What is the primary challenge associated with the long travel times for human missions to Mars, and how does it impact mission planning? 

– Health risks: radiation, lack of abort options.

– Need more supplies and careful planning.

Q78: What are the key components and functions of the Environmental Control and Life Support System (ECLSS) on the International Space Station (ISS)? 

– Regulates temp, pressure, air/water quality.

– Recycles ~93% of water and 40% of oxygen.

Q79: What resources on Mars could potentially be utilized to support human missions and "live off the land"? 

– CO₂, water ice, and minerals for oxygen, fuel, and food production.

Q80: What is "Space Adaptation Syndrome" and what percentage of astronauts does it typically affect? 

– Space motion sickness (nausea, vomiting).

– Affects ~70% of astronauts.

Q81: What causes astronauts to experience weakness upon returning to Earth after a long time in space? 

– Muscle/bone loss, fluid shifts, heart strain.

Q82: What are the two main sources of radiation in space, and how do they differ in terms of their characteristics and potential effects on spacecraft and astronauts? 

– Solar Cosmic Rays (SCRs): fast protons, partly shielded.

– Galactic Cosmic Rays (GCRs): high-energy, deeply penetrating.

Q83: How does radiation affect humans, and why is its effect described as "stochastic"? 

– Damage is probabilistic: can cause cancer even at low doses.

– Effect based on chance of DNA damage, not dose size alone.

Q84: What are the potential consequences of long-term exposure to low daily levels of radiation, and how can risks to astronauts be reduced? 

– Risks from chronic exposure uncertain (e.g., Mars trip).

– Shielding, medicine, and faster travel may reduce impact.

Q85:What are the three main psychological problems reported by astronauts after returning from long space missions, and why is selecting the right team crucial for the success of long-duration missions? 

– Sleeplessness, claustrophobia, social isolation.

– Team compatibility critical in confined missions.

Q86: What are the challenges in directly imaging exoplanets, and what are the two indirect techniques used to detect planets orbiting other stars? 

– Stars are too bright.

– Methods:

 • Reflex motion (wobble)

 • Transit dips in brightness

Q87: What are the challenges associated with interstellar travel, and what are the three possibilities for overcoming these challenges? 

– Nuclear-powered high exhaust velocity.

– Solar system-based lasers.

– Speculative: warp drives, wormholes.

Q88: What are some challenges associated with using atomic bombs as a propulsion system for interstellar travel? 

– Shielding, shock absorption, heat management.

– Legal bans on space nukes.

Q89: Name one proposed strategy to address the challenges of 1000-year interstellar journeys, and briefly outline a key ethical consideration associated with generation ships. 

– Suspended animation, embryos, AI, or life extension.

– Ethical concern: future generations can’t consent.

Q90: What happens when matter and antimatter come into contact, and why is antimatter considered an efficient energy storage option? 

– Annihilation releases gamma rays.

– Very high energy density (100× nuclear fusion).

Q91: Explain the concept of solar sails and lasers for interstellar travel and the challenges associated with the Breakthrough Starshot Initiative. 

– Light pushes sails; lasers provide high thrust.

– Problems: power, dust, targeting, communication, deceleration.

Q92: Explain the challenges associated with traveling at or near the speed of light according to Einstein's theory of Special Relativity. Also, briefly mention the speculative concept of cheating the light barrier using spacetime curvature and black holes. 

– Mass increases near light speed; needs infinite thrust.

– Speculative ideas: spacetime warping, black holes.

Q93: What is the Fermi Paradox, and what are some of the proposed explanations for why we haven't observed any alien civilizations in the Milky Way Galaxy? 

– If life is common, why haven’t we seen aliens?

– Possible reasons: rare life/intelligence, self-destruction, non-expansion, hidden civs.