Atmospheric Reentry

Atmospheric reentry is the process by which spacecraft from orbit of a planet or moon enter the atmosphere and reach the planetary surface intact. Typically this process requires special methods to protect against aerodynamic heating. Various advanced technologies have been developed to enable atmospheric reentry and flight at extreme velocities.

Planning an entry

Select the surface destination on the navigation instrument, then open REENTRY. ROUTE AUTO compares direct powered entry with coasting before entry. TARGET AUTO searches a controllable A/F handoff altitude and air-relative speed; H ALT and H TAS show its result. TARGET SET retains explicit values. HANDOFF selects the requested transition time. The automatic initial time is the earliest feasible handoff found in the candidate family. A later manual deadline can permit a more economical entry. Handoff is upstream of the destination, not touchdown.

The automated-entry controller can execute an ENTRY READY plan from orbit after undocking, using current loaded mass, forward/reverse mains and separate RCS limits. Its preview checks 95% of Vne and 200°C predicted AFT, with thrust, engine-response and attitude margins. It also checks the existing occupant and damage-dependent wing load limits, reserves 5% of that envelope, and rejects unplanned skip trajectories after the entry interface. These are guidance margins; continue observing the vehicle’s operating limits. The nose stays into the air-relative direction of travel during reverse braking. Active protection can sacrifice the requested time to brake, arrest excessive descent or recover an unplanned climb. LOAD LIMIT / RECOVER and SKIP LIMIT / RECOVER retain DOR control with bounded commands. See load and skip protection.

At the achieved atmospheric handoff, DOR sounds its disconnect once and transfers to aircraft guidance and TAS hold. FINAL HOLD captures altitude and heading. A valid runway FINAL ILS or VISUAL hands over descending in NAV/FPA/TAS, rather than leveling at H ALT. Both ILS and VISUAL continue with a nominal −20° descent and a gradual transition to at least 10 km of 3° final. Higher speed is retained until IAS/AFT or final braking requires slowing. ILS arms LOC/G/S near the join; VISUAL leaves the final segment to the pilot. NAV can converge from a lateral offset during descent; the VTOL preview does not automate descent, hover or landing. See arrival planning and the ILS handoff for the procedure and limits.

FPA is also available for pilot-selected atmospheric descent. Manual LOC arming and capture preserve managed vertical descent. Other pilot mode or target changes end automatic descent updates and retain the selected guidance. TAS hold can continue through supported NAV/LOC and vertical-mode changes. Cancel TAS hold with the DOR control or manual throttle input; disconnecting the aircraft autopilot also cancels it. The pilot remains responsible for ATC routing, terrain, configuration, flare and landing. The model does not forecast changing weather or terrain clearance.

Entry glow

Entry glow surrounds the vehicle and can be seen through the windshield and from external cameras. Its brightest region faces the relative airflow, moving toward the underside or side as attitude changes. Its appearance depends on air-relative speed and local atmospheric density, rather than a fixed altitude or Autoflyte engagement.

The glow is not a temperature gauge or a safe-flight indication. Continue to monitor AFT, IAS/Vne, dynamic pressure and flight path. Radio blackout and damage need not begin or end at the same time as the visible glow. Clouds and opaque cockpit or hull surfaces can obscure it. The flight simulator does not reproduce the entry glow.

AFT above 350°C progressively damages the windshield assembly, with damage accelerating sharply as temperature rises. Visible cracks develop as its condition deteriorates. Heating can continue to damage the windshield after wing loss; cooling stops further heat damage but does not repair it. A weakened windshield can cause fatal explosive decompression while it still has remaining structural condition, depending on cabin-to-outside pressure difference. AFT indicates airframe heating, not cabin-air or glass temperature. This thermal windshield damage is disabled in the flight simulator.

Methods

• Aerobraking uses atmospheric drag to remove orbital energy. It is not a promise that a Rise vehicle can tolerate an arbitrary unpowered entry. NASA's Mars Reconnaissance Orbiter first used a propulsive maneuver to enter Mars orbit, then spent about five months aerobraking to reduce that orbit. It did not take six months to first achieve orbital velocity. NASA mission operations reference.
• Powered entry combines engine braking with aerodynamic lift and drag. Rise ships use Iagreous fuel, but available thrust, loaded mass, engine response and atmospheric limits still matter. Reducing speed before entering denser air gives more margin than waiting for a warning and then demanding maximum reverse thrust.
• TVM is a velocity-control aid, not a complete entry controller. Its setting uses the selected target/reference and the ship's forward axis; it is not an airspeed or temperature limit. With a surface waypoint selected it uses a ground reference. See TVM and verify the selected target before engagement. TVM can command sustained thrust while opposing gravity, lift or drag; it does not guarantee suitable attitude, terrain clearance or a safe arrival.

Normal re-entry attitude

The manual example assumes wings level, with the nose generally into the relative airflow and the flight path aimed toward the destination. Pitch attitude and flight-path angle are different: monitor both instead of assuming the ship travels exactly where its nose points. Reverse main thrust permits braking while retaining a forward-facing attitude; lateral and vertical RCS have separate limits.

Deciding When To Drop

A heavy ship takes more time and distance to decelerate at the same thrust. Worked example, not a universal procedure: the original technique below assumed about 1.2 G acceleration in vacuum. Its distances, speeds and pitch angles depend on the vehicle, load and starting trajectory; do not use them as certified limits.
Vieneo has no sharp atmospheric boundary. Its density falls with a 7.5 km scale height; pressure, temperature and air-relative speed matter at the actual altitude. Plan entry for Vieneo's dense, nitrogen-rich atmosphere and the vehicle's loaded performance. At high altitude lift and drag may be weak, but 100 km is not a guarantee of negligible heating or dynamic pressure.
The worked example began reverse thrust at 100-120 km MSL, roughly 1500-1300 km from the target, and used upward translation to limit descent until ground speed was about 3 km/s. Those are example conditions, not a rule for when to start braking. A different mass, plane or arrival deadline can require substantially more distance.
In that example the ship then descended at roughly 2.5-3 km/s with the nose about 15 degrees below the horizon, while reverse thrust continued. Translation helped keep the flight path near the nose direction until aerodynamic lift could provide more control. Do not hold a fixed pitch regardless of IAS, AFT, dynamic pressure or descent trend. Use the configured upward/downward translation controls as required; the direction of the vehicle response matters more than a default key label.

Both air-relative speed and descent rate matter. Dynamic pressure varies with mass density and the square of air-relative speed. Heating also depends strongly on speed. Descent rate determines how quickly you encounter denser air; it does not make forward speed harmless.
Do not treat 5 km/s at 100 km, or any other speed/altitude pair, as universally safe. Watch AFT, IAS/Vne, dynamic pressure, flight path and available braking margin before conditions reach their warnings.

Slowing Down

The historical example aims for roughly 30 km MSL and 0.5 km/s before ordinary atmospheric flight. These are example values. TARGET AUTO selects a handoff for the current vehicle, mass, atmosphere and requested time; TARGET SET lets the pilot request specific values subject to the same feasibility checks. ILS or VISUAL continues descending toward the protected final segment. The pilot remains responsible for ATC routing, terrain and landing.

Points to Remember

• Avoid abrupt pitch or translation commands against large aerodynamic loads. To reduce descent, command the appropriate upward vehicle acceleration and adjust pitch within the available lift and load margin; do not confuse downward exhaust with downward vehicle motion.
• Do NOT roll inverted!
• If you are going to overshoot, prioritize a controllable trajectory over reaching the waypoint. Level off only if lift, thrust, airspeed and terrain permit it, then plan another approach.
• Do not force a late turn or steep descent to reach the target. Use practice flights and recorded results to establish repeatable margins for your vehicle and load.
• Your instruments are your friends, they will show you when danger is approaching, not the window.
• STAY CALM AND DO NOT PANIC!

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