9
$\begingroup$

Say you launch a satellite into GEO using Falcon9

The 1st stage returns

The 2nd stage is moved into graveyard orbit.

But what happens to the payload fairings?

Improve this question
$\endgroup$

2 Answers 2

Reset to default
25
$\begingroup$

A payload fairing is separated as soon as possible when the air is so thin that the payload needs no protection anymore. This reduces the weight of the remaining rocket. The fairing is usally separated at a height of about 100 km before the rocket is orbital. Therefore the fairing has a suborbital flight and reenters the athmosphere. Separating the fairing early leaves more fuel to be used for the payload. If the fairing would be separated just before the payload at orbit insertion, the maximal payload weight is reduced.

The fairing may be separated at the same height for LEO as well as GEO launches. It will not reach an orbit.

Improve this answer
$\endgroup$
1
  • $\begingroup$ Very informative answer. I checked some mission timelines and it separates at about 3:30 min after liftoff $\endgroup$
    – Joe Jobs
    Commented Aug 6, 2020 at 21:48
13
$\begingroup$

Like the first stage, SpaceX catches them and reuses them

Or at least that's the plan. They had their first successful single fairing catch in January this year, and their first successful double fairing catch in July. A new fairing costs around \$6m (\$3m per half), so reusing them reduces the cost of launches still further.

The fairing shells come down on parachutes but their guidance is relatively poor, so catching them in the net on the retrieval ship is still a new thing. Eventually it seems likely that this will be as routine as landing the first stage back on the barge is now, and losing anything will be the exception rather than the rule. For now, it's still in the early stages though.

Note that even if they miss, the parachutes should ensure splashdown is relatively gentle and the retrieval ship should still be close enough to pull them out. SpaceX have been pulling them out of the water for reuse up to now, so they aren't lost; the improvement this year is that they're now going to be caught on the ships. Contamination with salt water makes refurbishment more complex/expensive/longer, which is why SpaceX would prefer to catch them in the net on the ship and keep them dry.

According to the above link for the double fairing catch, the first reused fairing (i.e. one fished out of the sea and refurbished) flew last November.

(Edited to correct that fairings have already been reused.)

Improve this answer
$\endgroup$
7
  • 5
    $\begingroup$ @JoeJobs $6m for both halves. Added a link to the relevant SpaceX page to reference this. $\endgroup$
    – Graham
    Commented Aug 6, 2020 at 9:37
  • 2
    $\begingroup$ @JoeJobs No idea, sorry. It would seem logical, even if only to help locate a ditched fairing, but I don't know exactly how they're doing this. The barges are "only" required to hold position (harder than it sounds!) and the first stage flies to that fixed location, but the fairing is more like a carrier landing. The parafoil should be more steerable than the ship so it should be able to track the ship to landing, but it's coming down at a fairly steep glide angle with a high forward speed, and keeping a small ship on a steady straight line at that speed is harder. $\endgroup$
    – Graham
    Commented Aug 6, 2020 at 9:49
  • 3
    $\begingroup$ @JoeJobs: Having a GPS receiver would only mean the fairing knew where it was. For it to tell anything else where it was, it would need some way to transmit that. Perhaps as part of a locator beacon signal that a recovery vehicle could home in on directly, as well as by using the position data. (Yes, movies/TV always over-simply this to saying something "has a GPS tracker". Transmitting with enough power to be detected by some satellite network or whatever uses a lot more power than a GPS receiver needs, and the GPS satellites themselves definitely aren't listening.) $\endgroup$
    – Peter Cordes
    Commented Aug 6, 2020 at 20:10
  • 1
    $\begingroup$ The fairings are big things, it's probably easier to just use a ship-based radar. $\endgroup$
    – MSalters
    Commented Aug 7, 2020 at 7:11
  • 1
    $\begingroup$ @JoeJobs Yes, they do appear to have GPS. This 2018 article talks a bit about the fairings and the recovery process: teslarati.com/how-spacex-catches-fairing-mr-steven-net $\endgroup$
    – TylerH
    Commented Aug 7, 2020 at 13:27

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

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