Read on Twitter
Interesting questions, thank you. But there seems to be a misconception on what makes a FOBS.
As the name says, it is a Fractional Orbital Bombardment System, meaning it has to achieve orbit, if only for a fraction of that orbit. /1 https://twitter.com/mayank_p_grover/status/1349244214505213955
As the name says, it is a Fractional Orbital Bombardment System, meaning it has to achieve orbit, if only for a fraction of that orbit. /1 https://twitter.com/mayank_p_grover/status/1349244214505213955
To achieve orbit, you need to achieve orbital velocity. For the lowest stable Earth orbits, this is about 28,000 km/h, or 7.8 km/s (and do this in a direction parallel to Earth’s surface). There is no orbit, and therefore no FOBS, below that threshold. /2
This means your missile has to accelerate its payload to 7.8 km/s. And this payload than has to brake a little, perhaps .2 km/s, to initiate reentry of the Reentry Vehicle (RV) carrying your actual bomb(s). /3
This means you missile has to reach higher speeds than an ICBM (those start well below 7 km/s), while carrying a more complex and therefore heavier payload than an ICBM (RV plus propulsion for reentry burn, guidance system, attitude control, ...). /4
This means you missile has to be more powerful than an ICBM for the same RV. And this means it has to be bigger than the ICBM. Therefore, only big missiles of ICBM+ size can be used for FOBS. Where is that idea coming from that any big missile can be converted? /5
Anyways, there are no restrictions whatsoever in regard to propellant type or launch mode. The RV won’t care if it was brought to orbital speed by liquids or solids, or launched from land, truck, silo, submarine, or aircraft. If the SLBM is big enough, it could be converted. /6
If that makes sense is another question. Risks and costs are added by increased complexity, and flat reentry precision might strongly depend on current atmospheric conditions, which usually are not well known. A steeper ballistic reentry might be more accurate. 7/7 fin
