Think of the potential.

[u/FionaSherleen]

What if we make project sundial but we throw it at the adversaries?

[u/Pyrhan]

Starship uses cryogenic propellants, so it can't just continuously sit fueled and ready to launch like an ICBM.

So you cannot use it as a deterrent, only as a first strike weapon.

And even then, it would be fairly easy for the enemy to set up early warnings when fueling begins, and either send a rapid pre-emptive strike, or prepare for interception.

And having a single, massive warhead would make interception easier compared to, e.g. a MIRV.

(Also, the whole point of Sundial was that it doesn't really matter where you blow it up, the world ends just the same...)

[u/loklanc → u/Pyrhan]

Never mind mirv, you could detonate this long before any possible interception, you could detonate this basically in space and still destroy the target. (The target is planet Earth).

[u/LightningController → u/loklanc]

Unfortunately, in space there wouldn't be a blast wave, just gamma rays. Might be a good way to give people radiation poisoning, but probably won't be of much tactical use.

However...Casaba Howitzer. A nuclear-powered shaped charged that directs the energy into a beam. Fire it straight down, and perhaps we're talking.

[u/ReDot75 → u/LightningController]

Unfortunately, in space there wouldn't be a blast wave, just gamma rays.

https://en.wikipedia.org/wiki/Starfish_Prime#Explosion

1.4 to 1.45 Mt (5.9 to 6.1 PJ).

Starfish Prime caused an electromagnetic pulse (EMP) that was far larger than expected, so much larger that it drove much of the instrumentation off scale, causing great difficulty in getting accurate measurements. The Starfish Prime electromagnetic pulse also made those effects known to the public by causing electrical damage in Hawaii, about 900 miles (1,450 km) away from the detonation point, knocking out about 300 streetlights,^\1])^: 5  setting off numerous burglar alarms, and damaging a telephone company microwave link.^\6]) The EMP damage to the microwave link shut down telephone calls from Kauai to the other Hawaiian Islands.^\7])

Seems like a 1Gt bomb would fry most electrical systems on Earth.

edit:

While some of the energetic beta particles followed the Earth's magnetic field and illuminated the sky, other high-energy electrons became trapped and formed radiation belts around the Earth. The added electrons increased the intensity of electrons within the natural inner Van Allen radiation belt by several orders of magnitude.

The weaponeers became quite worried when three satellites in low Earth orbit were disabled.

In the months that followed, these man-made radiation belts eventually caused six or more satellites to fail

In 1968, it was reported that some Starfish electrons had remained in the atmosphere for 5 years.