Some more thoughts on TL6 air defense against Free Traders:
I whittled down the TL6 SAM to something that ended up being a bit less than SA-2 performance rather than a bit more. It still has a first stage booster that produces 500 kN and the second stage ("sustaining") engine produces 30 kN, which burns out after a total of 22 seconds of flight time. The trader is initially hovering 35 km downrange of the SAM site at an altitude of 30 km, so total slant range is 46.86 km. The moment it is fired on it produces maximum engine thrust (755370 kN against a mass of 77000000 kg) straight up. Gravitics are presumed to cancel the effect of gravity on the trader. True to physics 101, the planet is not rotating.
This is what the overall performance looks like:
The SAM reaches about Mach 3.3 by the time its engine burns out, and most of the acceleration is in the first 5 seconds, and net acceleration (from engine thrust, gravity and air resistance) reaches about 22.9g at 5 seconds. Immediately after the first stage boost is complete air resistance actually is stronger than engine thrust, but as the atmosphere thins out that fixes itself.
The second stage burns out and the SAM is ballistic at t=22s, about when it crosses 11615 meters altitude.
The guidance system itself is still not up to TL6 standards and the missile cannot bank against the atmosphere, but this gives a fair feel for the performance envelope of the SAM. It could probably reach a target at 30km altitude that was directly above it, but for a target downrange significantly a 30 km altitude (98000 feet) intercept is optimistic.
There could be a certain amount of fun for the simulation types in designing SAMs such that you have a mass limit and can select from several propellants with different exhaust velocities, and make tradeoffs of propellant mass vs warhead mass.
A TL6 government that has a requirement to at least attempt to intercept starships are probably going to need to build much more massive SAMs than our own SAMs of that era or import high TL defense systems, thanks to the ease at which starships can operate at much higher altitudes than TL6 aircraft can.
And setting aside acceleration, at 30km altitude my 800 Dton spherical ship modeled here has a maximum velocity equal to about Mach 45 (compared to about Mach 9.6 at 10km altitude). Missiles with peak velocities of around Mach 3.5 are going to have a hard time intercepting it, though given friction heating involved, I don't think they'd typically want to cruise around at Mach 45. That doesn't match the initial describe situation of a free trader lifting off from a planet and some force on the ground wanting to shoot it down, but something to keep in mind with respect to the defensibility of TL6 airspace from free traders.
-------- Original Message --------
On 2/9/2018 3:51 AM, Caleuche wrote:
1g acceleration actually feels quite sluggish at this scale, compared
to missile performance. If I can find performance information for the
Russian S-400 SAM/anti-ballsitic-missile system, I'll put that
together too and see if the ship can be threatened from a much further
distance.
Depending on how broad your view of TL6 is, you could see missiles with
between 20g and 100g accelerations, or more, with burn times of 10-30
seconds depending on the size and thrust of the missile. The take away,
for me, is that if the Free Trader is within the atmosphere, and within
the range of a non-manpad SAM, it isn't going to outrun it.
Kurt Feltenberger
“Before today, I was scared to live, after today, I'm scared I'm not living enough." - Me
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