14: Aiming at Pluto’s Heart — Part 2
New Horizons — $700 Million
Part 1 of this series covered Pluto’s discovery, its eccentric orbit and the importance of studying it closely. We also talked about its vast distance from Earth and how little we know about the Kuiper belt. Both these factors made New Horizons mission a scientific & an engineering challenge.
Building the Spacecraft
Solar energy was not going to be enough to power our spacecraft on its decade long voyage through deep space. Ironically, the dependable power source turned out to be Plutonium-238. As a bonus, heat from this radioactive material would keep the spacecraft warm.
Going so far out into the solar system also meant there was no possibility of a rescue after the launch. To ensure redundancy, backup systems were built for almost every major component of the spacecraft including the Guidance and Control processors. The team itself had to get through more than 200 contingency plans, perform dress rehearsals and have backup-to-the-backup teams ready to take over at a moment’s notice.
One does not get to the edge of the solar system by leaving things to chance — Eric Hand
The spacecraft designers also had to consider maneuverability of the spacecraft to perform tasks like taking pictures from different angles, communicating back with Earth and using the antenna as a shield from debris. For this purpose, engineers cleverly added 16 thrusters that could spin and rotate the spacecraft as needed.
The main objective of this long journey was to collect valuable scientific data about the Plutonium system that could not be gathered from Earth. The spacecraft carried 7 different scientific instruments to gather data on global geology, surface properties & atmospheric details of Pluto and its moons.
Team
It was clear that the spacecraft was going to require a team of dedicated humans to stay in touch on its decade long journey. This included gathering regular spacecraft signals like ‘I am alive’ updates, executing specific maneuvers during Jupiter flyby, troubleshooting issues and finally gathering scientific data when the spacecraft would reach Pluto.
NASA understood that this meant it was crucial to hire and train young minds well in advance. As it turns out, there was no shortage of young talented people looking to work for NASA. This strategy of investing early in people would pay huge dividends when the mission ran into issues just 10 days before its arrival to Pluto. More on that soon.
Launch
The amount of boost required for a 3 billion mile journey was going to be immense. Additional rocket engines were needed and a never used before 3rd-stage configuration was used to give that extra boost.
Alignment of the planets meant that to get any gravity assist from Jupiter, the launch window was tight. Delays in approvals and multi-agency coordination made this window even tighter. Alan Stern, the principal investigator of the mission, compared it to timing the launch of the spacecraft with a train going 500 miles an hour. On top of that, a Hurricane blew past the launch site while the rocket pieces were being put together. One of the rocket stages was severely damaged and had to be replaced.
It’s remarkable that the spacecraft actually lifted off on Jan 19th 2006 atop the mighty Atlas V rocket. This rocket gave New Horizons spacecraft 60 times the speed of a jetliner and the spacecraft zipped past theMoon in just 9 hours. Then in early 2007, Jupiter gave it another 2 miles per second boost, saving almost 3 years on its journey to Pluto. The Jupiter flyby also proved to be an excellent opportunity to test spacecraft’s scientific instruments.
Without all this effort & determination, we would not be enjoying pictures of Pluto’s big heart.
Losing Planetary Status
For all that was going well for the mission, Pluto itself was about to be ‘reclassified’. The International Astronomical Union (IAU) downgraded the status of Pluto to that of a dwarf planet. All because we recently discovered several similar sized objects around Pluto.
The initial definition stated that an object needs to have enough mass & gravity to become a sphere. Pluto satisfied this requirement. The new requirement was that the object also had to have cleared its vicinity of any debris. This was not true for Pluto.
As a result, in September 2006, Pluto got demoted to a ‘dwarf-planet’ — just another rock, stuck in the gravitational pull of our Sun.
Many on the New Horizons mission team didn’t agree with this classification change and publicly called IAU to revert Pluto’s status.
All this was going on while the New Horizons spacecraft was speeding towards Pluto. But it didn’t matter how humans classified it — Pluto was more interesting than we could have ever imagined. To be continued…
