Shadrak
10/16/15 09:29 AM
64.233.172.242
|
So, I was looking at thrust and since is is measured in g's (2 thrust points/g) I was looking for an analog in modern aeronautics...
The closest thing I can think is the thrust to weight ratio, but I didn't want to convert the formulas to confirm this...
Does anyone have an analog? If so, are you willing to share your formulas?
My best estimate is that modern fighters would have a safe thrust of about 2 with vehicles like a space shuttle having a thrust of 4/max thrust 6.
|
Cray
10/16/15 06:24 PM
72.189.109.30
|
Quote:
Shadrak writes:
So, I was looking at thrust and since is is measured in g's (2 thrust points/g) I was looking for an analog in modern aeronautics...
The closest thing I can think is the thrust to weight ratio, but I didn't want to convert the formulas to confirm this...
As you figured, thrust points in BattleTech, when applied to space, translate to 0.5Gs per thrust point. A 4/6 spacecraft is capable of 2Gs at safe thrust, or 3Gs at overthrust.
Thrust-to-weight ratio is the appropriate comparison in real life. Most real aircraft have considerably lower thrust than an aerospace fighter. A fighter that can pull 1G has about 2 thrust points.
Quote:
My best estimate is that modern fighters would have a safe thrust of about 2
Yep. A lightly burdened F-15 or F-22 may accelerate in a vertical climb, so they have a bit more than 2 thrust points. 2/3 would be a good model for their thrust. Further, they're limited to about mach 2.5, which is achieved with about 2 or 3 thrust points on the high altitude map.
Quote:
with vehicles like a space shuttle having a thrust of 4/max thrust 6.
Around that. However, the shuttle is difficult to model because of its widely varying tonnage but fairly constant thrust. It launches at about 1700 tons with 1.2Gs acceleration from the launch pad. It peaks at 3Gs when the SRBs are almost empty (about 2 minutes / 2 space turns into flight), then drops to about 1.5Gs when the boosters detach but the external tank is still pretty full. It gradually climbs back to 3Gs as the external tank empties out (remaining 6 minutes / 6 turns of the 8-minute launch).
Once the external tank drops, the main engines are useless and the shuttle is left with about 300m/s delta-V (1 fuel point) on its orbital maneuvering system (OMS). For a typical flight-configured orbiter of 240,000lbs, the total of 12,000lbs of thrust from both OMS motors equates to 0.05G / 0.1 thrust points, or half the thrust of a BT JumpShip or space station. (Even with the external tank retained, the shuttle's main engines are incapable of in-flight restarts. They were going to need a substantial redesign for in-flight starts on the new Orion.)
To frame the capabilities of BT spacecraft, the US shuttle's 300m/s and 0.05G are actually impressive by the standards of orbital spacecraft, and the shuttle had overpowered reaction control motors to flip and pivot - the Soyuz capsules are barely-maneuverable cannonballs in orbit with a fraction of the delta-V and thrust of the shuttle or US Gemini / Apollo capsules.
Mike Miller, Materials Engineer
Disclaimer: Anything stated in this post is unofficial and non-canon unless directly quoted from a published book. Random internet musings of a BattleTech writer are not canon.
|