We looked inside some of the tweets by @DuitsyWasHere and here's what we found interesting.
Inside 100 Tweets
13/ The Iskander and DF-12 also use thrust vanes. In these missiles, the vanes are used to help control the missile during boost, especially during the first seconds, while the missile accelerates away from the launcher. After main engine cut off, the vanes are useless.
12/ Thrust (jet) vanes are heat-resistant fins protruding into the rocket motor’s exhaust stream. Rotating the vanes changes the direction of the exhaust, steering the thrust. This is a form of thrust vector control. Some missiles (Scud, V-2, etc) rely on jet vanes exclusively.
8/ In this picture from yesterday’s North Korean launch, you can see the space between the fin and the missile body, as well as the location of the actuator shaft. The shaft is located in approximately the same position on the fin as in the Russian Iskander (third picture).
6/ Staying in the atmosphere avoids this problem. Even at 50,000 meters, where the atmosphere is very thin, control surfaces are still rather effective, and only require actuation motors and batteries to operate. In these pictures of ATACMS, you can see the fins and motors.
5/ In the vacuum of space, wings and control surfaces don’t work. Spacecraft must expend propellant in reaction control system thrusters in order to maneuver. Propellant has weight, so increasing maneuverability means increasing propellant weight, and reducing payload weight.
4/ How does it enable maneuvering? Staying in the atmosphere means dealing with atmospheric drag. This results in increased airframe heating and deceleration. However, it is also advantageous because it enables the use of aerodynamic control surfaces (steerable fins or wings).
3/ Depressed trajectories are used for several reasons: -Shorter flight time -Enables maneuvering to avoid defenses and increase precision -Takes longer for enemy radar to spot it (These figures do not represent the North Korean missile’s trajectory or range)
2/ Missiles like Russia’s Iskander, China’s M20/DF-12, the US ATACMS, and the new North Korean Missile fly on depressed trajectories, never leaving the atmosphere and maneuvering throughout the whole duration of flight. They are sometimes called “quasi-ballistic” missiles.
'Missiles like these will start the war': North Korea tests showcase growing capability. Experts weigh in on what Thursday's tests show about the new missiles https://www.reuters.com/article/us-northkorea-missiles-capability-analys/missiles-like-these-will-start-the-war-north-korea-tests-showcase-growing-capability-idUSKCN1SG0CR?feedType=RSS&feedName=newsOne …
1/ Was glad to help with this. Now that it’s out, I can give some explanations. I have the first nine tweets planned out. Then I’ll need to pause and write the rest This thread might end up rather long. I apologize in advance.
Initial reports put the apogee of the DPRK missiles at 50 km. That is too low for a ballistic trajectory at either stated ranges on a minimum energy trajectory.
If today's launches were of the new SRBM, then the range and apogee are actually in line with the Iskander-M (rather than the export model), though we still can't establish accuracy and maneuverability performance.
Want to see the May 4 North Korea missile launch in 3-D? @grace_c_liu and I took satellite images from our friends at @planetlabs and made a stereogram. You can view it with your phone using a #GoogleCardboard.
Can confirm that this works. Can also confirm that Jeffrey spent hours on this yesterday and was super excited by the result.