To all, this is about the time (1994) when a variant of Tu-160, Tu-160SK, was exhibited in Singapore, with a mock up of a small sat launcher (Burlak/Diana). Project involved Germany (sort of joint venture) but came to an end in 1998. So "Neptune" might just have been an analytic study of what could be expected from this kind of platform (performances, logistics, etc.) to understand how realistic Russian figures would be. B1B and Tu-160SK were close enough to compare apples and apples. I'm just very surprised that, as of today, and to the best of my knowledge, no such launch concept study was undertaken earlier than that with/for B1A. Given engineers always love to perform these kinds of studies, and puch the product envelop, it is highly improbable this type of study does not exist. Maybe someone will, one day, unearth one such thing and we can open a new thread. Plus: being not an ASAT, these types of satellite launcher concepts, are likely not to be forbidden by any disarmament treatises. Cheers.