How many feet per second does a shell move where the height range is 23500?
CREATE TABLE "table1_16439764_1" (
  "gun" text,
  "m_v_ft_s" real,
  "shell_lb" text,
  "time_to_ft_m_at_25_seconds" text,
  "time_to_ft_m_at_40_seconds" text,
  "time_to_ft_m_at_55_seconds" text,
  "max_height_ft" real
);
SELECT MIN("m_v_ft_s") FROM "table1_16439764_1" WHERE "max_height_ft"=23500;