Discussion Elon Musk: the F9 first stage can reach orbit as an SSTO.

[MaverickSawyer]

I think that it's more of a case of "possible, but not practical" for now.

Besides, unless you deorbit the booster, it's going to be a major hazard. Kessler syndrome much?

 

[PhantomCruiser]

Minor quibble.

Most people agree that SSTO is possible but is not feasible.

And pretty pointless until affordable.

 

[Urwumpe]

And pretty pointless until affordable.

And pretty expensive for pointless fun.

 

[PhantomCruiser]

Kind of reminds me of something I saw in an interview with James Dyson (60 minutes or something like that). He was showing off stuff they'd made in the labs, it was the worlds most efficient clothes washer. Completely useless because it was also completely un-affordable (well beyond $10K).

If the almighty bean-counters had determined that SSTO was on the plus side of a cost-benefit analysis, it would be commonplace. Until such time, it'll more than likely be fantasy.

 

[Urwumpe]

If the almighty bean-counters had determined that SSTO was on the plus side of a cost-benefit analysis, it would be commonplace. Until such time, it'll more than likely be fantasy.

Exactly. And if it would be on the border of being potentially profitable, somebody would dare his luck.

 

[RGClark]

Hello.... read again: Nobody denies that it is technologically feasible to build a SSTO.
Everybody just knows that it is economically foolish to build one at the current technological variables.
If you can find a billionaire, you can sure build a SSTO without a purpose except getting launched once for millions of USD to show that it is possible.

You ignored the point I was making. Do the calculation for the F9 first stage payload assuming it has the 340 s vacuum Isp of a Merlin Vacuum by using altitude compensation.

Bob Clark

 

[MaverickSawyer]

You ignored the point I was making. Do the calculation for the F9 first stage payload assuming it has the 340 s vacuum Isp of a Merlin Vacuum by using altitude compensation.

Bob Clark

And you're missing Urwumpe's point... It's an academic argument, since it's not going to actually happen.

 

[Urwumpe]

You ignored the point I was making. Do the calculation for the F9 first stage payload assuming it has the 340 s vacuum Isp of a Merlin Vacuum by using altitude compensation.

Bob Clark

Prove that an altitude-compensated nozzle reaches the same performance at sea level as a vacuum optimized nozzle in vacuum.

 

[C3PO]

The importance of doing the F9 first stage launch as an SSTO, even at low or little payload, is that it would remove the mental block that SSTO's can't be done at all.

We've removed the mental block that unicycles are possible, but still most people go for bicycles.

 

[Col_Klonk]

Solved SpaceX's reusable problem

Elon needs to get the right people with the right ideas for his reusable program..
https://www.dropbox.com/s/bl7zqwge0y8pg1x/ReusableStage.mp4?dl=0 (17MB)

 

[RGClark]

Elon needs to get the right people with the right ideas for his reusable program..
https://www.dropbox.com/s/bl7zqwge0y8pg1x/ReusableStage.mp4?dl=0 (17MB)

It proposes using parachutes to land the stage rather than the engines. One problem with that is that if you want to return to the launch site it wouldn't give you sufficient accuracy in the landing area.

Bob Clark

 

[Andy44]

Besides, unless you deorbit the booster, it's going to be a major hazard. Kessler syndrome much?

Only a problem at higher altitudes. At lower altitudes the booster will deorbit due to drag after a few weeks or months. Not a perfect solution, but this is very common.

 

[garyw]

The tweet suggests the payload will be less, not zero. The upper stage is a significant portion of the cost.

Surely the payload of the first stage IS the second stage? :lol:

 

[Col_Klonk]

It proposes using parachutes to land the stage rather than the engines. One problem with that is that if you want to return to the launch site it wouldn't give you sufficient accuracy in the landing area.
Bob Clark

I haven't put the extendable wings on yet, nor programmed the return journey... It's is meant to be more humourous than practical.. but you never know.
:thumbup:

 

[RGClark]

The argument has been made that giving the F9 first stage hovering capability would reduce its payload. However, some simple and low cost modifications would allow hovering and actually increase the payload:

Hovering capability for the reusable Falcon 9, page 3: hovering ability can increase the payload of a RLV.
http://exoscientist.blogspot.com/2015/12/hovering-capability-for-reusable-falcon.html


Bob Clark

 

[Thunder Chicken]

The only mild advantage of SSTO would be that you'd only be disposing of one stage vs. two. But that is more than offset by the massively reduced payload to orbit. SSTO is a neat trick, it suggests a high performance booster, but it doesn't make for cheap orbital rocket systems.

1st stage recovery is the best of both worlds - only losing the upper stage, AND you get a good payload to orbit. It makes better economic sense to pursue this vs SSTO even though it may be technologically more difficult.

 

[Hlynkacg]

The argument has been made that giving the F9 first stage hovering capability would reduce its payload. However, some simple and low cost modifications would allow hovering and actually increase the payload...

That exoscientist guy you linked to is an idiot.

The only way to give the F9's 1st stage hover capability is to make it significantly heavier or develop a new engine that has both deep throttle capability and a ISP equal to or greater than the existing Merlins. Those are not "cheap" or "simple" modifications by any means.

 

[Pipcard]

That exoscientist guy you linked to is an idiot.

I'll take a guess that you haven't noticed that RGClark is the same person as "that exoscientist guy." So please be more civil, even if you disagree with the argument presented.

 

[Hlynkacg]

I'll take a guess that you haven't noticed that RGClark is the same person as "that exoscientist guy." So please be more civil, even if you disagree with the argument presented.

I hadn't, and I do feel a bit sheepish now, but the point remains...

Does "Δv = Ve * ln[M / Me]" or doesn't it?

 

[RGClark]

I hadn't, and I do feel a bit sheepish now, but the point remains...

Does "Δv = Ve * ln[M / Me]" or doesn't it?

You didn't read what the modifications were. Two types were discussed. Both already exist, i.e, no new technology, and are low cost.
In regards to the rocket equation, one increases Ve, and the other reduces Me, i.e., the burn-out mass.

Bob Clark