const orbitalPeriod = arr => {
  const GM = 398600.4418;
  const earthRadius = 6367.4447;
  const root = 2 * Math.PI
  const orbitalPeriods = arr.map(elem => {
    let avgAlt = elem.avgAlt 
    delete elem.avgAlt 
    const numerator = (earthRadius + avgAlt)**3 
    const innerRoot = Math.sqrt(numerator / GM) 
    const orbitalPeriod = Math.ceil(innerRoot * root); 
    
    
    return {
      ...elem,
      orbitalPeriod
    }
  })
  return orbitalPeriods
}
orbitalPeriod([{name: "iss", avgAlt: 413.6}, {name: "hubble", avgAlt: 556.7}, {name: "moon", avgAlt: 378632.553}]);