Weapon Specification: Magrathean Guided Nuclear MissilesCopy Anchor Link

"'It is most gratifying,' it said, 'that your enthusiasm for our planet continues unabated, and so we would like to assure you that the guided missiles currently converging with your ship are part of a special service we extend to all of our most enthusiastic clients, and the fully armed nuclear warheads are of course merely a courtesy detail. We look forward to your custom in future lives... Thank you.'"

— The Hitchhiker's Guide to the Galaxy, Chapter 17

The Magrathean Guided Nuclear Missiles are the automated planetary defence ordnance of ancient Magrathea. Maintained in deep subterranean silos beneath the permafrost during the civilization's five-million-year cryogenic sleep, these weapons remain in permanent, fully armed standby status, linked to the automated receptionist system of the Commercial Council of Magrathea.

Tactical SpecificationsCopy Anchor Link

• Visual Profile: Two gleaming silver darts that rise vertically through the upper stratosphere, transforming under magnification into massively real rockets thundering through the sky with supersonic shock diamonds.
• Targeting & Guidance Jamming: Equipped with advanced ancient ECM (electronic countermeasure) suites that selectively jam incoming spacecraft guidance computers—completely disabling the automated evasive navigation of Sirius Cybernetics shipboard mainframes like Eddie.
• Warhead Payload: High-yield thermonuclear warheads delivered as an automated "courtesy detail" for persistent uninvited guests.
• Maneuverability: Capable of executing screeching high-G banking turns when targets attempt radical evasive dives, re-locking onto a head-on homing pursuit within seconds.

The Intercept Engagement with Heart of GoldCopy Anchor Link

When Zaphod Beeblebrox ordered the Heart of Gold to commence descent into Magrathea's atmosphere despite polite recorded warnings to leave:

1. The Launch: The missiles climbed rapidly from the barren grey surface beneath the ship.
2. The Guidance Jam: Eddie reported that automated guidance systems were locked out, counting down impact from forty-five seconds.
3. The Manual Dogfight: Scurrying across manual consoles, Ford Prefect pulled guidance rocket levers, executing a screeching 180-degree reversal straight toward the rockets before a snapped lever sent the ship into an uncontrolled dive, causing the missiles to shoot narrowly past the hull.
4. The Second Approach & Improbability Jump: Banking in a screeching arc, the missiles locked back onto the ship's tail at impact minus five seconds—just as Arthur Dent manually engaged the unprogrammed Infinite Improbability Drive.

The Improbability Transmutation (Chapter 18)Copy Anchor Link

At impact minus five seconds, the raw improbability wave generated by firing the drive without proofing screens caught both thermonuclear missiles in mid-flight:

• The $8,767,128$ to 1 Transmutation: At an improbability factor of eight million seven hundred and sixty-seven thousand one hundred and twenty-eight to one against, the solid rocket fuel, guidance electronics, and thermonuclear warheads suffered instant atomic transubstantiation.
• The Result: The first missile was transformed into a very surprised-looking Sperm Whale, while the second became a Bowl of Petunias. Both items plummeted through the Magrathean atmosphere, terminating in a wet thud and a cloud of ceramic shards upon the barren planet below.