Chapter 7

7.1 The Case for Reusability

Launch cost is the single greatest barrier to access to space. Traditional expendable launch vehicles use hardware worth tens to hundreds of millions of dollars once and then discard it. This is like flying an airplane on a single trip and then scrapping the airplane.

7.1.1 Cost Structure Analysis

The figures above are rough public estimates, not audited data. Key insight: propellant accounts for less than 1% of the total cost. Reusing the hardware can cut costs by a factor of 10 or more.

7.2 History of Reusable Launch Vehicles

7.2.1 Space Shuttle (1981-2011)

It was the first partially reusable launch vehicle, but it failed to deliver the revolutionary cost reduction it had aimed for.

Reusable Components

• Orbiter: the Space Shuttle itself
  • 135 flights (5 orbiters)
  • Months of refurbishment required
  • More than 30,000 tiles inspected individually
• Solid Rocket Boosters (SRB):
  • Splashdown in the ocean under parachutes
  • Disassembled, cleaned, and reassembled after recovery
  • Segments reused over many flights

Expendable Components

• External Tank: a new one for every launch
  • Reason: the delta-v cost of recovery exceeded the cost of building a tank
  • Destroyed during atmospheric reentry

Why Did Cost Reduction Fail?

• Enormous refurbishment costs: months of work after each flight
• Low launch rate: an average of 4-5 per year (target: 50)
• Complexity: millions of parts, each requiring inspection
• Result: cost per launch ~$450M-$1.5B (depending on the accounting method)

7.3 Falcon 9: The Reusability Revolution

SpaceX's Falcon 9 is the first orbital-class rocket to achieve truly economical reuse.

7.3.1 Recovery Process

RTLS (Return to Launch Site) Recovery

Landing at the launch site - the most impressive but also the most difficult method

1. T+0:00 - Liftoff
2. T+2:30 - MECO (Main Engine Cutoff): first-stage engines shut down
   • Altitude: ~70 km
   • Velocity: ~6,000 km/h
   • Position: tens of km east of the launch pad
3. T+2:33 - Stage separation
4. T+2:40 - Boostback Burn:
   • Three engines reignite (~20 seconds)
   • The first stage flips toward the launch site and decelerates
   • Delta-v: ~1,000 m/s
5. T+3:00 - Free fall:
   • Ballistic descent for about 4 minutes
   • Grid fins deploy → attitude control
6. T+6:40 - Entry Burn:
   • Three engines ignite (~20 seconds)
   • Velocity: ~5,000 km/h → ~1,000 km/h
   • Purpose: reduce aerodynamic heating and loads
7. T+8:00 - Landing Burn:
   • The single center engine ignites (~30 seconds)
   • Velocity: ~1,000 km/h → 0
   • Altitude: ~1,000m → 0
   • "Suicide Burn": maximum deceleration at the last moment
8. T+8:30 - Touchdown
   • Four landing legs deploy
   • LZ-1 or LZ-2 landing zone
   • Precision: within a few meters of the center

ASDS (Drone Ship) Recovery

Landing at sea - more common, and it preserves payload capability

• Differences:
  • No boostback burn
  • Follows a ballistic trajectory to the downrange drone ship position
  • Entry burn + landing burn only
• Drone ship:
  • Size: 52m × 91m
  • Position: hundreds of km downrange from the launch site (Atlantic or Pacific)
  • GPS station-keeping (accuracy: ±3m)
  • Names: "Of Course I Still Love You", "Just Read the Instructions" (references to science fiction novels)
• Challenges:
  • A moving target (waves)
  • A small landing area
  • Many failures in the early days (2015-2016)
  • Today: a near-100% success rate

7.3.2 Reuse Records

7.3.3 Refurbishment Process for Reuse

Post-Recovery Procedure

1. Recovery (from the landing zone or the drone ship):
   • Land landing: lowered to horizontal by crane
   • Drone ship: secured and towed to port (~2-5 days)
2. Transport: by trailer to a SpaceX facility
3. Inspection:
   • External inspection: grid fins, landing legs, airframe
   • Engine teardown inspection
   • Plumbing and valve checks
4. Refurbishment:
   • Engine replacement (as needed)
   • Landing leg reassembly
   • Touch-up of thermal protection on the engine section and interstage
5. Static fire test: required before each re-flight by WIA-SPACE-004 §8.2 (SpaceX itself now often omits it for flight-proven boosters)
6. Relaunch preparation: payload integration

Shrinking Turnaround Time

• Early days (2017): months of refurbishment
• 2018-2019: 2-3 months
• 2020-2021: 1-2 months
• Today (2023+): a few weeks, with record turnarounds under two weeks
• WIA-SPACE-004 §8.3 targets: under 30 days for Falcon 9-class vehicles; under 24 hours (aircraft-like operations) as the Starship-class goal

7.3.4 Fairing Recovery

Fairings are also reused for additional cost savings ($6M per flight)

• Recovery method:
  • Attitude control with cold-gas thrusters after separation
  • Parachute deployment
  • Recovery vessel attempts to catch them in a net (early method, difficult)
  • Today: recovered after splashdown in the ocean (more reliable)
• Reuse: recovered fairings are cleaned, inspected, and reused

7.4 Falcon Heavy: Three-Core Reuse

Falcon Heavy is a super-heavy rocket made of three Falcon 9 cores strapped together, and recovery is attempted for all three.

7.4.1 Configuration

• Center Core: reinforced structure
• Side Boosters × 2: nearly identical to the Falcon 9 first stage
• Second stage: identical to Falcon 9

7.4.2 Recovery Scenarios

Side Boosters

• Separation: T+2:30 (early separation)
• Boostback: immediate return to the launch site
• Landing: simultaneous landings at LZ-1 and LZ-2

Center Core

• Separation: about T+3:05 (later separation, higher velocity)
• Recovery: drone ship (hundreds of km downrange)
• Challenge: reentry at very high velocity → many early failures
• Outcome: landed once on the drone ship (Arabsat-6A, 2019) but was lost in heavy seas; center cores are often expended on high-energy missions

7.5 Starship: The Dream of Full Reusability

SpaceX's ultimate goal is a fully reusable launch system.

7.5.1 Starship Configuration

• Super Heavy (first stage):
  • Height: ~70m
  • Engines: 33 × Raptor
  • Propellant: liquid methane + liquid oxygen
  • Thrust: ~72,000 kN (the most powerful in history)
• Starship (second stage/spacecraft):
  • Height: 50m
  • Engines: 6 × Raptor (3 sea-level + 3 vacuum)
  • Payload: 150+ tons to LEO
  • Capable of reentry and landing

7.5.2 Recovery Methods

Super Heavy

• Boostback: return to the launch pad
• Landing: caught in mid-air by the launch tower's "Chopsticks" (mechanical arms)
  • No landing legs needed → weight savings
  • Can be placed back on the launch mount immediately
  • First tower catch: October 2024 (Flight 5)
  • Target: rapid relaunch after the catch

Starship Spacecraft

• Reentry:
  • Belly-first reentry (high drag)
  • Stainless steel + heat tiles withstand the heating
• Belly Flop: horizontal descent
• Flip Maneuver: flips to vertical just before landing
• Landing: vertical landing under engine thrust (at the launch pad or a remote location)

7.5.3 Development Status

• Test flights: multiple high-altitude tests
  • SN8, SN9, SN10: landing failure or explosion
  • SN15: first successful landing (2021-05)
• Orbital test flights:
  • 2023-04: first integrated flight attempt (lost control and was destroyed by the FTS)
  • 2023-11: second attempt (hot-stage separation successful; Starship lost late in its ascent burn)
  • 2024-10: fifth flight; first catch of Super Heavy by the launch tower arms
  • Testing and improvements continue
• Goals:
  • Crewed lunar landing as the NASA Artemis Human Landing System
  • Uncrewed Mars cargo missions (SpaceX target)
  • Crewed Mars missions (long-term SpaceX goal)

7.6 Economics of Reusability

7.6.1 Cost Analysis

Falcon 9 launch cost analysis (illustrative model based on rough
public estimates; not SpaceX data):

Expendable launch:
- First stage manufacturing: $28M
- Second stage manufacturing: $10M
- Fairing: $6M
- Operations: $5M
- Profit: $18M
Total launch price: $67M

Reused launch (first stage flown 10 times):
- First stage amortization: $28M / 10 = $2.8M
- First stage refurbishment: ~$1M
- Second stage (new): $10M
- Fairing (reused): $1M
- Operations: $5M
Internal cost: ~$20M → sold at ~$50M

Price reduction for the customer: ~$17M/launch (about 25%)
Margin for the operator: roughly $30M instead of $18M

7.6.2 Economies of Scale

• Higher launch rate:
  • SpaceX 2023: 98 launches (No. 1 in the world)
  • A cadence made possible by reusability
• Starlink business model:
  • Requires launching thousands of satellites
  • Economically impossible without reusability
  • Low launch cost → Starlink service becomes viable