Some of my Facebook friends get all giddy about the SpaceX rocket landing in a barge and amazed at its precision. Some even called it the greatest thing in space travel and it got me thinking, really? OK, the launcher was recovered, that’s great, but precision? This thing barely broke out of the Earth’s atmosphere.
I looked into the splashdown of the Apollo spacecrafts. The moon mission that was the most accurate in hitting the designated splashdown point was Apollo 16 (0.55 miles) and the less accurate was Apollo 12 (5 miles). The distance between the Earth and the Moon is 230.100 230,100 miles or for M.O.A. calculations, 404,976,000 yards. According to the formula, the MOA for a Apollo spaceship splashdown should have been 4.240,098.72 yards or roughly 2,409 miles.
Apollo 12 had an M.O.A. of 0.00207. Apollo 16 was almost ten times less. (Do check my math. I have been wrong before.)
And that was a space program run with less computing power than the cheapest smart phone in the market and most of the engineers used slide rules to do the math and calculus.
So, no. Not impressed just yet with SpaceX.
“The distance between the Earth and the Moon is 230.100 miles.” We’re in ‘Merica, so that should be a comma — 230,100 miles. Other than that, I agree with you about the level of impressiveness. 🙂
Try to keep up with two systems and get back to me, you crud! 😀
When you want to get into stuff that is truly amazing. We used the same technology to guide our orbiters on landing as we used for our nukes on delivery. Guidance is guidance. A few time we splashed down within a few hundred feet of the aircraft carrier that was going to pick up the Apollo capsule. So yes, we could launch an ICBM and not just hit a Russian city with it, but pick the building in the city we wanted to hit.
The Russians also used the same tech for space recovery as nukes (why not?). They landed their capsules on land because they had an accuracy of a 500 mile radius. If they aimed for the ocean, which is a softer landing, they couldn’t guarantee that they could get to the capsule before it sunk. So they aimed for the dead center of Russia and equipped the cosmonauts with survival gear. Which means, if the Russians ever tried to get us with ICBMs; if they aimed at Washington DC, they could only guarantee a hit inside of a circle that went north to south from Charleston, SC, to Portland, ME, and east to west from Lexington, KY to somewhere in the Atlantic.
Guidance System like the AK sights built by Century Arms.
Speaking as an aerospace guy, a few thoughts:
1. True, Apollo was amazing, I’m not discounting that.
2. 0.55 miles after 230,000 miles is 0.00239 mils (easier than MOA)
3. SpaceX landed within 1-2 ft of the center, after ~200 miles, or 0.00095-0.00189 mils, or ~1.25-2.5x better
That said, the best comparison that proves your point is Apollo was an open loop targeting (similar to aiming a gun), while Falcon uses closed loop tracking of the ship for its final landing (also, Falcon is a guided propulsive landing, Apollo was parachutes, etc)
So the better argument is Apollo was <3x worse WITHOUT closed loop last-mile guidance AND subject to wind drift on the parachutes…which is WAY more impressive
Side note:
New Horizons had to target a box 100x150km after traveling 5 billion km, a required error of +/-0.000015 mil (6-12x better than spaceX) with only 3 correction burns (totalling <0.3% of total delta-v)
The equivalent would be Apollo landing within about 20 ft of the target.
Not to discount the Apollo missions in the slightest, but the ballistics for that could be calculated in realtime using an applet on this forum without significantly affecting anyone’s browsing experience. The orbits of Earth and the Moon are well-recorded and not liable to change suddenly, while the platform that Falcon had to land on was actively moving and tilting in 6 degrees of freedom.
On the other hand the scientists of the 1960s managed to hit the moon using computational power dwarfed by the average pocket calculator of today, and that is no mean feat.