The NPR News item What's Iran Up To With Recent Rocket Launch Attempt? by NPR's Geoff Brumfiel, about a recent launch test in Iran includes the following:
Earlier this week, Iran attempted to launch a rocket carrying a satellite into space. The Trump administration says their goal is really to develop long-range weapons. NPR's Geoff Brumfiel looks into what Iran is up to.
Markus Schiller is the founder of ST Analytics, an independent consultancy in Germany. He's spent a lot of time looking at Iran's space program, and he says there are links to the military. For example, the engines Iran uses on its space rockets have a military origin.
MARKUS SCHILLER: It's actually a missile engine.
BRUMFIEL/NPR: But Schiller says it's not a very good missile engine. It's an old design from the Soviet Union, picked up by the North Koreans and later transferred to Iran. It's clunky and inefficient. To get even a small payload into space requires the rocket to be huge. It takes weeks to set up.
Also, Schiller says, based on photos, Iran's space rocket can't work as a missile. The second stage is just too small. To him, the launch looks nonthreatening.
Question: What actual engine are they talking about, and in what way is it "not a very good missile engine"? Why would this engine require "the rocket to be huge"?