Close Menu
TechCentralTechCentral

    Subscribe to the newsletter

    Get the best South African technology news and analysis delivered to your e-mail inbox every morning.

    Facebook X (Twitter) YouTube LinkedIn
    WhatsApp Facebook X (Twitter) LinkedIn YouTube
    TechCentralTechCentral
    • News

      Blue Label Telecoms to change its name as restructuring gathers pace

      11 July 2025

      Get your ID delivered like pizza – home affairs’ latest digital shake-up

      11 July 2025

      EFF vows to stop Starlink from launching in South Africa

      11 July 2025

      Apple plans product blitz to reignite growth

      11 July 2025

      Nissan doubles down on South Africa despite plant uncertainty

      11 July 2025
    • World

      Grok 4 arrives with bold claims and fresh controversy

      10 July 2025

      Bitcoin pushes higher into record territory

      10 July 2025

      Cupertino vs Brussels: Apple challenges Big Tech crackdown

      7 July 2025

      Grammarly acquires e-mail start-up Superhuman

      1 July 2025

      Apple considers ditching its own AI in Siri overhaul

      1 July 2025
    • In-depth

      Siemens is battling Big Tech for AI supremacy in factories

      24 June 2025

      The algorithm will sing now: why musicians should be worried about AI

      20 June 2025

      Meta bets $72-billion on AI – and investors love it

      17 June 2025

      MultiChoice may unbundle SuperSport from DStv

      12 June 2025

      Grok promised bias-free chat. Then came the edits

      2 June 2025
    • TCS

      TCS+ | MVNX on the opportunities in South Africa’s booming MVNO market

      11 July 2025

      TCS | Connecting Saffas – Renier Lombard on The Lekker Network

      7 July 2025

      TechCentral Nexus S0E4: Takealot’s big Post Office jobs plan

      4 July 2025

      TCS | Tech, townships and tenacity: Spar’s plan to win with Spar2U

      3 July 2025

      TCS+ | First Distribution on the latest and greatest cloud technologies

      27 June 2025
    • Opinion

      In defence of equity alternatives for BEE

      30 June 2025

      E-commerce in ICT distribution: enabler or disruptor?

      30 June 2025

      South Africa pioneered drone laws a decade ago – now it must catch up

      17 June 2025

      AI and the future of ICT distribution

      16 June 2025

      Singapore soared – why can’t we? Lessons South Africa refuses to learn

      13 June 2025
    • Company Hubs
      • Africa Data Centres
      • AfriGIS
      • Altron Digital Business
      • Altron Document Solutions
      • Altron Group
      • Arctic Wolf
      • AvertITD
      • Braintree
      • CallMiner
      • CambriLearn
      • CYBER1 Solutions
      • Digicloud Africa
      • Digimune
      • Domains.co.za
      • ESET
      • Euphoria Telecom
      • Incredible Business
      • iONLINE
      • Iris Network Systems
      • LSD Open
      • NEC XON
      • Network Platforms
      • Next DLP
      • Ovations
      • Paracon
      • Paratus
      • Q-KON
      • SevenC
      • SkyWire
      • Solid8 Technologies
      • Telit Cinterion
      • Tenable
      • Vertiv
      • Videri Digital
      • Wipro
      • Workday
    • Sections
      • AI and machine learning
      • Banking
      • Broadcasting and Media
      • Cloud services
      • Contact centres and CX
      • Cryptocurrencies
      • Education and skills
      • Electronics and hardware
      • Energy and sustainability
      • Enterprise software
      • Fintech
      • Information security
      • Internet and connectivity
      • Internet of Things
      • Investment
      • IT services
      • Lifestyle
      • Motoring
      • Public sector
      • Retail and e-commerce
      • Science
      • SMEs and start-ups
      • Social media
      • Talent and leadership
      • Telecoms
    • Events
    • Advertise
    TechCentralTechCentral
    Home » In-depth » The amazing science behind SpaceX’s Falcon 9

    The amazing science behind SpaceX’s Falcon 9

    By The Conversation14 April 2016
    Twitter LinkedIn Facebook WhatsApp Email Telegram Copy Link
    News Alerts
    WhatsApp
    The SpaceX rocket approaching the landing platform
    The SpaceX rocket approaching the landing platform

    On Friday, 8 April 2016, SpaceX’s Falcon 9 rocket launched a mission to deliver a spacecraft called Dragon with its payload of supplies and experiments into a trajectory towards the International Space Station (ISS). Most remarkably, the first-stage booster then landed on a ship (see video below).

    This is no easy task. Think back to 1969 when the Apollo 11 mission delivered three astronauts to the moon. Neil Armstrong and Buzz Aldrin walked on the moon while Michael Collins piloted the command module in lunar orbit. All three returned safely to Earth.

    The first stage of the huge Saturn V rocket that launched them into space burned for about three minutes and then crashed into the ocean. The second stage burned for a further six minutes, taking the craft into near-Earth orbit. It too was jettisoned and then burned up during its descent to Earth. The third stage burned for nine more minutes to send the astronauts towards the moon — again burning up on re-entry. The Saturn V rocket, at a cost of US$6bn in 1969, was completely lost.

    On the astronauts’ return, only the command module splashed down in the Pacific Ocean. Of the 140t of metal that was launched, only 5t returned to Earth. And at launch, the mission carried a staggering 3 000t of fuel … more on this later.

    Just imagine the cost saving if the Saturn V had been able to return to Earth almost intact — and then land itself to be used on another mission. Well, as the latest SpaceX landing proves — along with the reusable technology being developed by Blue Origin — that dream is becoming reality.

    Of course, there have been reusable spacecraft before. The space shuttle was intended as a reusable spacecraft. The orbiter returned to Earth landing like a conventional aircraft, and the two solid rocket boosters could be recovered from the sea. Only the huge orange external tank would burn up, but getting the spacecraft ready for the next flight was slow and expensive.

    The SpaceX philosophy is that the majority of the rocket can be rapidly recovered, refuelled and re-flown, making for significant cost savings. Fuel is less than half a percent of the cost of the mission, so there is potential to decrease the cost of getting to space dramatically.

    SpaceX’s Falcon 9 rocket blasts off
    SpaceX’s Falcon 9 rocket blasts off

    The rocket science bit

    But what of the rocket science? Well, the ISS is in “near-Earth orbit”, at an altitude of about 400km. This is less than the distance from London to Paris, albeit straight up. It is orbiting at a speed of about 7,7km/s — it only takes about 90 minutes to go once around the Earth.

    So how much energy does it take to deliver 1kg of payload to the ISS? First, think of kinetic energy (KE) — yes, you learned this at school. At 7,7km/s, the KE per kilogram works out at about 30 megajoules (MJ). But you also need to consider gravitational potential energy (GPE) — yes, you did this at school, too. The force of the Earth’s gravity doesn’t change very much over this short distance upwards given that the Earth’s radius is 6 400km. So it’s easy to work out that the GPE needed to lift 1kg up to 400km is only about 4MJ. This is small compared with the 30MJ of KE required.

    But not only do you need to get your payload to 7,7km/s, you have to carry the fuel in your tanks as well. Thanks to Konstantin Tsiolkovsky’s “ideal rocket equation”, however, we know that liquid fuels, which have a faster gas jet speed, are more efficient than solid fuels. Essentially, by using liquid fuel, each 1kg of payload needs a minimum of 4,5kg of fuel to reach a speed of 7,7km/s, while with solid fuel, you’d need more than 20kg — and this is before taking the rocket mass into account. This is a very good reason why rocketeers, including SpaceX, prefer to use liquid fuels; with a high gas jet speed, the launch mass is much less.

    The secret of SpaceX

    So, how does SpaceX’s rocket work? The Falcon 9 is a two-stage launch vehicle. Each stage uses a liquid fuel with liquid oxygen (very similar to the kerosene and liquid oxygen fuel used in the Saturn V — chemistry hasn’t changed in 50 years). Falcon 9’s first-stage “booster” is by far the largest and most expensive component of the launch mass and it makes sense to try to recover it for re-use — it’s no good to have it splash into the sea because the resulting damage and corrosion would render it useless.

    On 8 April, SpaceX made history by landing the Falcon 9 on an automated barge. See the entire story of its development in this video created by Kinematic:

    And so SpaceX has developed the Falcon 9 booster so that it can land on a ship. The idea is that shortly after main engine cut-off and stage separation, the booster flips over and directs itself towards an unmanned drone ship that is waiting as a landing pad.

    During its descent, the booster reaches speeds of around 1 000m/s (double this after more adventurous geostationary missions) but its fins and engines control the speed and direction of the Falcon, slowing it down as it approaches the Earth. At the last minute, four legs then deploy — and it makes a soft landing at a speed of less than 6m/s. All of this delicate navigation is performed by on-board computers and inertial navigation systems.

    The landing is so fast that no human could react quickly enough to ensure a smooth touchdown.

    To make things trickier, the ship is pitching, rolling and heaving in the sea. It’s hard enough for pilots to land on an aircraft carrier — Falcon is a tall slender column some 20 storeys high. Once the Falcon has landed, the legs lock out rigidly. In one of the earlier Falcon missions, one of the legs failed so even though the landing was a success the Falcon fell over shortly after, resulting in a huge conflagration. But that’s why they use an unmanned drone ship as a landing platform — no one gets hurt. Of course, it’s easier to land on land — and the Falcon does this if the mission flies over land. But the ability to land at sea adds flexibility.

    What next?

    Falcon 9 and Dragon are paving the way for a new generation of low-cost reusable spacecraft — and SpaceX is already developing Dragon to launch and return up to seven astronauts into orbit and beyond. Perhaps next, there’ll be a refuelling base on the moon? Then Mars is an awful lot closer.

    The flexibility offered by reusable vehicles is the stuff of science fiction — the classic movie Star Wars and more recently The Martian and Interstellar are nothing without spaceships that launch at the push of a button. We’re not there yet, but with spacecraft that can hop around like aircraft, then anything is possible.

    The author wrote this piece with the assistance of one of his former Trinity students, Lars Blackmore, who now works for SpaceX as principal rocket landing engineer. Blackmore graduated with his MEng from Cambridge in 2003 and a PhD from MIT in 2007. He is now responsible for landing Falcon 9.The Conversation

    • Hugh Hunt is reader in engineering dynamics and vibration, University of Cambridge
    • This article was originally published on The Conversation


    Elon Musk Falcon 9 Hugh Hunt Lars Blackmore Nasa SpaceX
    Subscribe to TechCentral Subscribe to TechCentral
    Share. Facebook Twitter LinkedIn WhatsApp Telegram Email Copy Link
    Previous ArticleHumanity could reach the stars within a generation
    Next Article Union wants ANN7 bailout

    Related Posts

    EFF vows to stop Starlink from launching in South Africa

    11 July 2025

    Grok 4 arrives with bold claims and fresh controversy

    10 July 2025

    The satellite broadband operators taking on Starlink

    9 July 2025
    Company News

    $125-trillion traded: Binance redefines global finance in just eight years

    11 July 2025

    NEC XON welcomes HPE acquisition of Juniper Networks

    11 July 2025

    LTE Cat 1 vs Cat 1 bis – what’s the difference?

    11 July 2025
    Opinion

    In defence of equity alternatives for BEE

    30 June 2025

    E-commerce in ICT distribution: enabler or disruptor?

    30 June 2025

    South Africa pioneered drone laws a decade ago – now it must catch up

    17 June 2025

    Subscribe to Updates

    Get the best South African technology news and analysis delivered to your e-mail inbox every morning.

    © 2009 - 2025 NewsCentral Media

    Type above and press Enter to search. Press Esc to cancel.