29
$\begingroup$

The Lunar X-Prize winning condition was "landing a robot on the surface of the Moon, traveling 500 meters over the lunar surface, and sending images and data back to the Earth."

The Falcon Heavy test payload was a Tesla Roadster with multiple cameras. The static engine test was one day after the X Prize Foundation announced nobody would claim the prize by the deadline, but launched 53 days before the deadline passed.

If Musk had wanted to win that prize, could he have done so with that payload? (Presumably telling the foundation that an attempt would be pending the result of the engine test so they didn't prematurely call an end to it).

If not, what further changes would the payload (/final stage) have required to win?

$\endgroup$
  • 1
    $\begingroup$ Using the Falcon 9 as rocket to get a Lunar X-Prize contestant into space would be an intriguing idea. $\endgroup$ – gwally May 15 '18 at 13:41
  • $\begingroup$ I wonder if thinking about the rover for the X-Prize was the origin of the idea to launch a Tesla? $\endgroup$ – JollyJoker May 15 '18 at 14:19
  • 6
    $\begingroup$ I'm guessing that ploughing it into the surface of the moon at a million miles an hour is a lot easier than landing it $\endgroup$ – Richard May 15 '18 at 21:56
  • 1
    $\begingroup$ Where would you have to apply to get permission to land on the moon? Is there a fee? What about reserved areas - like existing landing sites to be preserved for future space tourism? Or protected sites because of... natives? (half silly, half kinda serious) $\endgroup$ – Criggie May 16 '18 at 8:57
  • 1
    $\begingroup$ @Criggie you mean..[~~shudder~~] there might be lunar parking enforcement officers? $\endgroup$ – Martin James May 16 '18 at 21:08
47
$\begingroup$

The rocket probably had the power to do it, however there were numerous challenges:

  • The Tesla is not a moon rover, its batteries and motors were not designed for a vacuum with the extremes of heat and cold it would have been exposed to on the lunar surface. The wheels are too small for rough terrain and some suspension components would crack in the extreme cold. You'd have to do a huge amount of expensive design and development and the result would be the shell of a Tesla with completely different innards. It would be much more practical and probably to design a rover from the ground up for that purpose, which would be much smaller
  • The lander would have to be designed around the roadster, which is bulky, or use some sort of skycrane design. Both options are doable, but again would require massive investments in research and development. The size of the roadster would present real problems in getting the whole deal inside a fairing

Doing this would have taken years of R&D and a big lake of money, plus it would have taken attention away from what they really wanted to do, which was prove the rocket. A failure to land on the moon would have tainted the whole enterprise even if the rocket were successful.

$\endgroup$
  • 11
    $\begingroup$ As Musk said himself about that launch "It’s a win if it just clears the pad". You really don't want to pour a ton of money into R&D when your chance of even leaving the atmosphere is so low. $\endgroup$ – Ordous May 15 '18 at 17:28
  • 2
    $\begingroup$ I'm sure the success criteria Musk expressed privately were a bit more than that, but I agree @Ordous $\endgroup$ – GdD May 15 '18 at 17:31
  • 3
    $\begingroup$ You could probably drive 500m without suspension and with flat tires on some parts of the moon. I think overheating could be a much bigger issue for the electronics than the cold. $\endgroup$ – Michael May 16 '18 at 8:44
  • 3
    $\begingroup$ I'm thinking the cold is more a problem for the batteries @Michael. The electronics would have a mix, some would get too hot, others would have problems operating in the cold, like the electric motors. If you kept it slow 500 meters would probably be okay heat-wise. $\endgroup$ – GdD May 16 '18 at 8:49
  • $\begingroup$ Good answer, I have got an opportunity to visit one of the participating company, only the engineering goes to the wheel for preventing dust issues is huge. $\endgroup$ – Jithin Jose May 16 '18 at 9:21
20
$\begingroup$

Without changes, no. The Falcon Heavy test didn't include a lander, so no way to get the Roadster to the Moon in one piece.

You need about 2.5 km/s of delta-V to get from Earth escape to the lunar surface. Some of that (~0.7 km/s) could be provided by the second stage, that gets you to a low Moon orbit, but the 1.73 km/s from LLO to lunar surface has to be provided by a lander.

Plugging a dry mass of 2500 kg (i.e. 1000 kg of structure and engine, 1500 kg Roadster), 1.75 km/s of dV and the use of RP1 into this calculator gives me an initial mass of 4000 kg, which seems doable.

In addition to the lander, the car has to be modified for remote control and communications (camera, a charged battery pack, a transmitter/receiver capable of reaching Earth, remote control hardware). Separation hardware between second stage and lander. Build the lander on top of the car (with rocket nozzles along the sides of the car) and leave it attached to the car after landing.

(assumption: the second stage can provide enough delta-V to get to low Lunar orbit).

$\endgroup$
  • 6
    $\begingroup$ Was it required to arrive in one piece? The roadster could skid 500m over the surface while disintegrating ^^ $\endgroup$ – PlasmaHH May 16 '18 at 9:09
  • $\begingroup$ It could very easy be spread over 500 meters or more @PlasmaHH! $\endgroup$ – GdD May 16 '18 at 9:24
  • $\begingroup$ If it's lithobraking, try 500 km instead of 500 m. Lunar escape velocity and atmospheric drag are so low that smaller parts would likely orbit the moon a few times before coming to rest. $\endgroup$ – Camille Goudeseune May 16 '18 at 18:35
8
$\begingroup$

A Falcon Heavy without reuse has a capacity of about 20tons to Low Lunar orbit (interpolating between the figures for GTO and Mars on wikipedia). The dry mass of the upper stage is about 4tons (spaceflight 101), and say 2 tons for an adapted Roadster, leaves about 14 tons of propellant for the upper stage to attempt a propulsive landing on the moon. With an Isp well over 300 seconds, that's loads of delta-V and thrust, so it seems like we could hope to bring the upper stage briefly to stationary just above the lunar surface. We're short of a few things like landing legs, so we'd probably have to eject the roadster "over the side" and supply it with airbags (on the outside) to survive the "landing". With a lot of luck, though, it might roll 500m (either in the airbags, or on its wheels) and claim the prize.

$\endgroup$

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.