Bunker buster technology
Look Here.
...Additionally, altering the shape of the projectile, to incorporate an ogive shape has yielded substantial results. Rocket sled testing at Eglin Air Force Base has demonstrated penetrations of 100 to 150 feet in concrete when traveling at 4,000 ft/s. The reason for this is liquefaction of the concrete in the target, which tends to flow over the projectile...
Yes no where near what's need to penetrate the average depth of Europa's ice, but way more than the 7-8 meters you mention.