I actually found another figure that shows how weird Piper’s distances are. It’s six months from Uller to Niflheim, according to *Uller Uprising*:

“Well, it takes six months for a ship to go between here and Nif,” Prinsloo considered. “Because of the hyperdrive effects, the experienced time of the voyage, inside the ship, is of the order of three weeks.”

But it’s *also* six months from Uller to Terra – which is 21ly!

“He’d get away with it for just welve months—the time it would take to get the news to Terra and for a Federation Space Navy task-force to get here. And then, there’d be little bits of radioactive geek floating around this system as far out as the orbit of Beta Hydrae VII.”

This is inconsistent in the extreme, as Niflheim at a described 148ly from Earth can’t possibly be 21y from Uller. Surely, the Navy wouldn’t take, say, eight months or more to get a task force ready.

Of course, it is telling that the text passage mentions Beta Hydrae, not Beta Hydri. Beta Hydrae is another star, at 370 +/- 40ly from Earth!

Overall it’s quite clear Uller actually is at Beta Hydri, though.

So ignoring that flaw (the two names are easily confused after all) and assuming “half a years” consists of a rounded 180 days – since it’s also unclear where Niflheim actually is, we can’t really use it to calculate the speed of the hyperdrive. Note that the time difference between hyperspace and realspace was a concept that Piper dropped later.

If we assume that the travel time for earth is correct, we get roughly 0,005 to 0,007 ly/h.

*Four Day Planet* states that a light-year takes about 60 hours:

All the news is at least six months old, some more than a year. A spaceship can log a light-year in sixty-odd hours, but radio waves still crawl along at the same old 186,000 mps.

Note the “sixty-odd”, so it’s not exactly sixty.

Later in the book, it’s stated that Walt will go to Terra for six years; five years on Terra itself for studies and one year for the round trip.

If we calculate 180 days * 24h = 4320 hours, and travel 650 light-years during that time we get 0,15 ly/h. All’s well, right?

Not quite. The problem arises when we calculate 650 light-years times 60 hours per light year. That’s 39000 hours, or 1625 days, or almost four and a half years – for a one way trip! Clearly there’s something broken here. 0,15ly/h works out to 6,67 hours per light year. Factor of ten issue, but which one do we believe? It’s got to be the higher speed, because I can’t imagine that many people would travel all the way to Fenris if it took them 9 years to get home.

This seems so blatantly wrong that I wonder if I have a glaring error in my math.

Anyway; using *Four Day Planet’s* figure of sixty hours per light year for the trip from Uller to Terra. that voyage should take ~53 days. That’s a far cry from the “6 months” mentioned in *Uller*, but 106 days plus preparation time is still too long a time to depend on if your natives are revolting.

*Space Viking* states quite bluntly that a hyperdrive travels at roughly 1ly/h:

A ship in hyperspace logs about a light-year an hour.

Again, this gives us some leeway in our interpretations – it’s not exactly one light year. It could be less, or more – 10% either way, at least.

*Little Fuzzy* gives us an indirect figure for hyperdrive speed:

They’re on Terra, five hundred light-years, six months’ ship voyage each way.

Assuming 180 days for half a year, we get a speed of about 2.78 light years per day, or 0.115 light years per hour. Fits pretty well with the assumed 0,15ly/h from *Four Day Planet*, especially if it’s slightly more than 500ly and less than half a year. At 0,15ly/h the trip from Zharathrustra to Earth would take 138 days.

*Ministry of Disturbance* has a very vague figure:

A ship on hyperdrive could log light-years an hour

Since it’s plural, that means 2ly/h or better. It probably needs to be much more if the Empire is truly galactic.

Story | Speed (ly/h) |

Uller Uprising | 0,005 – 0,007 ? |

Four Day Planet | likely 0,15 |

Space Viking | 1 |

Little Fuzzy | 0,115 |

Ministry of Disturbance | 2+ |

Even with the rough numbers we have, it’s clear that there was a tenfold increase in hyperspace speed between the early days of the Terran Federation to the time of Space Vikings, and probably another such jump in drive performance by the time of the Empire.