2
$\begingroup$

It is common knowledge know that SpaceX uses the landing barges when the requirements for the first stages are so high that a return-to-base is not achievable. This seems to occur both in case of GTO and LEO missions. This is clearly not ideal, since it involves transportation delay, cost and risk.

That makes me wonder: Are the trajectories between different large mass LEO and GTO missions that much different? Could SpaceX setup a plant somewhere closer to the expected landing zones to minimize transportation time and cost (e.g. airlift recovered boosters). Preferably some island, but also a large swimming platform might suffice.

$\endgroup$
  • 3
    $\begingroup$ The expected landing zone is in the middle of the ocean. Setting up a factory there is prohibitively expensive. $\endgroup$ – Hobbes Jun 16 '16 at 9:51
  • 1
    $\begingroup$ @Hobbes if Elon needs a tropical island in the middle of the ocean to build a factory, it'll probably happen. Every supervillain needs one. Not only will an isolated island lower employee attrition, but it helps to hide both the thermonuclear devices and the sharks with lasers. $\endgroup$ – uhoh Jun 20 '16 at 3:09
4
$\begingroup$

Once SpaceX has a continuous pipeline of rockets being launched, refurbished, and reused, the latency -- the time it takes for a single stage to go from launch to launch-ready -- won't matter.

If the turnaround time is, say, 70 days, and SpaceX has 10 first stages in their stable, they can maintain a launch cadence of 1 per week. 4 ASDS would probably be sufficient to service the fleet at that time - at a given time there might be one on station, one unloading a stage, one being refurbished, one on the way out to sea.

Speeding up the barge trip is solving a non-problem.

$\endgroup$
3
$\begingroup$

The last few missions doing GTO boosts have had the ASDS in reasonably close to the same location in the ocean. The lower energy CRS-8 mission was further in shore, since it had the performance to come back that much closer to shore.

There is a fair bit of variability possible, but it does appear that there is little benefit in going much further east, since if there was, for the SES-9 (That crashed hard), and the other high performance missions they would have taken advantage of that.

There might be a limit on how far they want to tow an ASDS out to sea, manage it for a day or three and bring it back. It does take about 4-5 days to get to the current GTO landing spot. The support ships have been shown to have fuel supplies sufficient, but there might be a crew usage issue.

Additionally, missions to GEO like orbits have some options. GEO is harder than GTO both due to performance, but also due to restart and coast issues.. GTO requires that the upper stage/payload do more of the work to get to GEO than a direct injection into GEO. SpaceX usually does GTO not GEO launches, because their second stage cannot coast long enough on batteries and make it GEO, thus they quote GTO, in which there are several standards for delivery.

Depending on the orbit, the payload itself needs to expend more energy to get to full GEO, which either takes a long time (Electric thrusters) delaying entry into service by months, or else reduces its on orbit life span by using up the fuel to get there.

$\endgroup$
  • 1
    $\begingroup$ Falcon 9 currently cannot launch directly to GSO/GEO. The second stage is not cryogenic and lacks battery life iirc. $\endgroup$ – jkavalik Jun 16 '16 at 13:45
  • $\begingroup$ @jkavalik what does "not cryogenic" signify? No LOX? Why does that mean "...can not launch directly to GSO/GEO"? Also, is there really a need for a lot of battery power during the ~10 hour ride to the top? $\endgroup$ – uhoh Jun 20 '16 at 3:19
  • 1
    $\begingroup$ @uhoh the LOX is cooled to ~-200°C and RP-1 is cooled to -7°C. As I understand it - in space during the time to the apogee lot of the LOX will boil away but the kerosene would actually solidify as the temperatures try to equalize. When both components of propellant are cryogenic, good enough insulation to keep both cold should be enough. About the batteries - for now the stage needs to stay online for ~35 minutes for GTO, not sure exactly how much for deorbit from LEO, but say 5-10x the battery life is needed an batteries are a bit heavy so they eat from the payload. $\endgroup$ – jkavalik Jun 20 '16 at 18:33
  • 1
    $\begingroup$ During the search I found a comment stating that even in case of these not being prohibitive, the payload to GEO would be about 1.4T only (compared to 5.5T for GTO, so before a thrust upgrade). Not sourced but I suppose thats because you have to put the stage itself to GEO and it weights ~4T. $\endgroup$ – jkavalik Jun 20 '16 at 18:42
  • $\begingroup$ @jkavalik OK I see now that maintaining the LOX and RP-1 for another 10-12 hours would require a substantial redesign of thermal management. The rest makes sense too. Thanks! $\endgroup$ – uhoh Jun 21 '16 at 0:30
1
$\begingroup$

For now, no. The landing zone is in the middle of the ocean. Setting up a factory there is prohibitively expensive.

IIRC, the long-term plan is to launch from somewhere further West so they can land at Cape Canaveral. That would require flying over land, which requires FAA permission which isn't easy to obtain, This probably requires lots more flights before the FAA considers the rocket to be proven enough to allow it.

$\endgroup$
  • 1
    $\begingroup$ Imho no. If the FAA ever approves this, the F9 will be probably already deprecated and the next generation is rumored to be designed to have the margins to always RTLS. $\endgroup$ – jkavalik Jun 16 '16 at 13:52

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.