Photo courtesy of NPS
The Comet Falls trail is still closed due to damage from an avalanche. You can get more information and see images from the NP at Mt. Rainier NP on their Facebook page about the damage and the work ahead. The Comet Falls traihead is on the highway between Longmire and Paradise, see map.
There is an alternate route to Van Trump Park via the trailhead for two routes, one at Longmire on the Rampart Ridge trail and one at the trailhead east of Longmire, part of the Wonderland trail, both of which meet the Van Trump trail. These trails bypass the Comet Falls trail but requires you return the same route.
This adds considerable distance to Van Trump Park and Mildred Point so include this time in your plans. There is no known time to repair the trail as the snow will have to melt first before the trail maintenance work can begin, but expect it to take well into mid-August at the earliest.