>     The Hop drive is quantized to 10 parsecs per jump, and each level
> beyond that is another 10x multiple. The usual workaround is to aim
> for the gravity well of a star at your destination, but short of the
> 10pc. That just makes the Navigation that much more difficult.
And higher orders are likewise quantised to their respective multiple? 
eg skip drives would be quantised to 100 pc, leap drives to 1 kpc, etc?
>
>     The TL 17 Hop drive relies on two technology discoveries. Stable
> Antimatter power and quantum field generation.
>
>     The BHHR is akin to a liquid fuel rocket. It produces a great deal
> of energy in a very short period of time. But like the rocket, the
> reaction is barely controlled and directed to a single purpose. Now
> you can use the same basic reaction in a more controlled fashion and
> get the same or more energy from it, but that won't produce the same
> effects.
>
>     Each level of the jump drive (J2,..J6, etc) requires larger and
> larger quantities of energy. J10 energy requirements are impossible to
> meet, and a J8 would be the theoretical maximum and still have a ship
> to move.

Depending on relative costs, I (reaching somewhat) could see a case for
continued J-8/J-9 use despite H-1 being available, because of quantum.

MGT2 lets you build jump drives at higher TL than their base and (for a
cost premium) reduce the fuel burn.  IIRC, reduction is in steps of 5%
of total fuel burn, and tops out at 15%.  A J-8 drive could thus burn
only 68% of ship's displacement (at +3 TL to the J-8 base), and a J-9
drive would burn 76.5% of ship displacement.

I did say I was reaching.

>
>     Antimatter power, which isn't just dump some antimatter into
> magnetically shielded chamber with some matter and capture the
> produced particles for energy, but rather <more handwavium> process of
> direct conversion to energy. Basically, if you have the mc^2, you can
> get all the E you need at any rate your machine can handle it. Which
> is good because the field create a HopDrive Hop requires a power slug
> with close to a kg of antimatter.
Wait wait wait... if you've got matter conversion to energy going
(through <more handwavium>), why do you need to bother with antimatter?
>
>     The Quantum field, first discovered with the Black Globe
> generators, generate both the field to create the Hop insertion and
> the field to protect the ship while transitioning through the Hop
> space wormhole. No pressurized hydrogen which can fail and let the
> wormhole space intrude and destroy the ship. Makes the Jump / Hop
> process much safer.
>
>     It is possible to build an anti-matter/field generator version of
> the Jump Drive. It requires a fraction of the power the hop drive
> does, and the huge fuel tanks on the ships all go away. The <now
> simple> engineering problem is distribution of the Antimatter
> technology to ensure a fuel supply. The equipment to generate
> antimatter on that scale is not small or cheap.
>
>     Even still, many of the Hop Drive ships also mount a AM powered J1
> or J2 Jump drive. Usually as an emergency measure in case of misjump,
> a much more likely event as the Astrogation calculations now exceed
> most Sophont + Advanced Computer ability to prove safely complete.
> Fixing that to allow the higher scale drives requires another TL
> advance in computer technologies which won't come until TL 20 or beyond.
>
<snip>

From what you've described, a J-3 drive would be a good complement to
any strain of Hop drive to allow fine(r) positioning inside that last 10
pc, at the cost of an extra week in transit.

Modulo fuel concerns, I guess trying to fire up one drive while underway
on the other would simply be a rather pants-on-head method of suicide?