Not having tried the device, but looked at how it works, and the information given by the inventor, it seems plausible to me that it could in fact
work. Specially the astral time travel part seems very legitimate, and since it is a radionics device it is basically already something using so
called "unscientific" means to work: "psychic energy".
Looking at it in a pure traditional "scientific" way will not do the most good here since science (orthodox / traditional / public ) is not up to
date when it comes to what can only be called "spiritual energies" and "psychic powers" etc.
It is however interesting, for those whom may not know, that governments have been using more or less the same approach for decades in espionage etc,
such as the Stargate Project. Here is a documentary featuring various CIA agents talking about their involvement and experiences with using astral
projection (in the form of "remote viewing") for spying and other means:
One do not need any device to achieve the effects this device, the HRD, is supposed to be able to induce, but yes it can be quite possible that it may
help achieve such effects much easier and quicker than most people are able to do without it, and from doing only meditations and astral projection
exercises on their own. There are many different devices able to help with astral projection, from light strobe goggles to various hemi-sync soundwave
based technology, to hypnosis etc. Would a machine such as the HDR be safe to use? Probably not long-term or frequently, considering the way it works
with electricity and electromagnetism.
Also regarding the mentioned grid points, or vortexes, these energy spots on Earth, these are in fact very strong energy sources that can be used
among many other things for teleportation and time travel (both which are more or less the same and directly linked to each other). On that I can only
speak from personal experiences, and once I did actually travel through time into the future on such an energy spot. It was a short "travel" though,
only 6 hours into the future, but nevertheless it gave me the understanding of how powerful such spots are. It was also quite by accident, and
happened to both me and a friend at the same time, and other witnesses were able to confirm us having been gone for those hours in addition (in fact
we did not even know about it until we met other family members and friends whom had been wondering if we had gotten lost as we were up in the
mountains and woods at the time).
So yes, time travel is certainly possible, both astrally and physically. Verified and experienced both, and I hope you succeed with your experiments
without causing yourself any injuries or problems.