According to Mitchell Burnside Clapp:
Black Horse is a name that has four different meanings. First, it is a gesture of respect to the British "Black Knight" and "Black Arrow" programs, which used hydrogen peroxide and kerosene as rocket propellants. Black Arrow put the 100 kg Prospero satellite in a polar orbit in October 1971. Secondly, there is Native American symbolism to Black Horses, said among the plains indians to have powers the ordinary horses lack. Also they are omens of ill fortune if they appear without warning on your horizon, something enemies of the republic should bear in mind. Third, it pokes a bit of fun at the SR-71, because birds are nice, but a horse can carry something. Last, the vehicle can fairly be said to be a "Dark Horse" candidate in the space lift sweepstakes.
Hydrogen peroxide has a density of 1.432 g/cc in 98% strength, while LO2 at normal boiling point has a density of 1.142 g/cc. But the mixture ratio of interest is 7.3 Ox:Fuel rather than 2.6. As a result, a H2O2/JP-5 machine has a bulk propellant density of 1.33 g/cc, rather than the 1.00 g/cc you need for LO2/RP-1. Also, you can _use_ JP-5 instead of fancy coolant-grade hydrocarbons. The density increase is not marginal. All other things being equal, you take a 18 second Isp penalty with respect to a LO2/RP design. For the Black Horse mission (DV=26500 fps) you need a mass ratio of 10.5 for LO2/RP-1 and 11.6 for H2O2/JP-5. When you multiply by the density, you get a volume advantage of about 20% for the H2O2/JP-5 system. Since the weight of tankage is strongly correlated to its volume (see the Atlas SSTO thread, for example), you are likely to wind up ahead on your structural weights for a H2O2 system. Also, you can skip the cryo insulation on the LO2 side.
NASA's standard code for trajectories, called POST, gives a result of 26,500 fps for the DV to orbit from tanker release. I would be surprised if Pegasus was only picking up 1000 fps. Are you sure it's not 1000 m/s?
Peroxide is not explosive or detonable, and I have copious literature to substantiate that assertion. It will decompose in the presence of impurities, and so you must be clean and safe in handling the stuff. The standard of cleanliness is the same as for LO2. Meet the standards, and you can handle it like water. Come to think of it, you can even flush lines with water, something you can't do with LO2 systems. The worst ting you can say about it is that it costs more than LO2, about 70 cents/pound vs. 5 cents/pound.
I thought the thing that scuppered Ti for the shuttle orbiter was the low thermal conductivity of Ti. It can handle more temperature, but hot spots are much more likely to burn through than with Al. Al has thermal conductivity over 15 times that of Ti Alloys.