Airlock

SpaceX: Current missions and future plans. (Renamed thread.)

8381 posts in this topic

16 hours ago, DarthVader said:

It's unclear weather dream chaser will fly in a fairing or not, the renderings for the cargo version (the one likely to fly) has folding wings to fit in a standard 5 meter fairing.

It's pretty clear that it flies inside a fairing.

Share this post


Link to post
Share on other sites
5 hours ago, Nibb31 said:

It's pretty clear that it flies inside a fairing.

A manned version wouldn't be able to fly inside a fairing, would it?

Share this post


Link to post
Share on other sites

Meanwhile, in the non-SpaceX world, ULA has sent Cygnus otw to station in  their predictably perfect, boring way. Maybe we need a ULA thread. They might be "boring," but that's cause they get the job done, almost every time. Was fun to watch Centaur lifting the perigee post-apogee, then circularizing with RCS before the deorbit burn. 

2 people like this

Share this post


Link to post
Share on other sites
9 minutes ago, tater said:

Meanwhile, in the non-SpaceX world, ULA has sent Cygnus otw to station in  their predictably perfect, boring way. Maybe we need a ULA thread. They might be "boring," but that's cause they get the job done, almost every time. Was fun to watch Centaur lifting the perigee post-apogee, then circularizing with RCS before the deorbit burn. 

Nah, I'll stick with the "Innovations with a chance of explosions" channel. Come to see the future, stay for the floor show. :D

besides, this thread has the attention span of a sugared-up two-year-old...

3 people like this

Share this post


Link to post
Share on other sites
26 minutes ago, tater said:

Meanwhile, in the non-SpaceX world, ULA has sent Cygnus otw to station in  their predictably perfect, boring way. Maybe we need a ULA thread. They might be "boring," but that's cause they get the job done, almost every time. Was fun to watch Centaur lifting the perigee post-apogee, then circularizing with RCS before the deorbit burn. 

WHY DO YOU HATE SPACEX

Kidding, kidding.

The 360-degree video wasn't nearly as cool as I was anticipating, mostly because the launch itself was like...3 frames.

2 people like this

Share this post


Link to post
Share on other sites
27 minutes ago, CatastrophicFailure said:

Nah, I'll stick with the "Innovations with a chance of explosions" channel. Come to see the future, stay for the floor show. :D

besides, this thread has the attention span of a sugared-up two-year-old...

Heck, my sugared-up two-year-old can stick with one subject longer than this thread can.

2 people like this

Share this post


Link to post
Share on other sites
23 hours ago, sevenperforce said:

Winged recovery is a mixed bag. I know it's not something SpaceX is considering. Aerodynamics for the launch of a winged second stage is really tough; that's why the X-37 launches inside a fairing.

Then launch it in fairing and recover winged part... you will lose only fairing.

Share this post


Link to post
Share on other sites
27 minutes ago, IllyrianTheGreat said:

Then launch it in fairing and recover winged part... you will lose only fairing.

They don't make a fairing big enough for the entire second stage.

Share this post


Link to post
Share on other sites
1 hour ago, sevenperforce said:

A manned version wouldn't be able to fly inside a fairing, would it?

There was an ESA concept for a capsule on Ariane that would use an LES under a special quick-release fairing. SNC probably aren't doing that with DC, but it is possible.

Share this post


Link to post
Share on other sites
9 minutes ago, Kryten said:

There was an ESA concept for a capsule on Ariane that would use an LES under a special quick-release fairing. SNC probably aren't doing that with DC, but it is possible.

Right. Technically Orion has a fairing, but it is attached to the LES and jettisoned with it.

In any case, it's one thing to put a fairing around a spacecraft; it's another altogether to put a fairing around an entire stage.

Share this post


Link to post
Share on other sites
1 hour ago, sevenperforce said:

Heck, my sugared-up two-year-old can stick with one subject longer than this thread can.

And only moderately more prone to explosions. :D

1 person likes this

Share this post


Link to post
Share on other sites
2 hours ago, sevenperforce said:

A manned version wouldn't be able to fly inside a fairing, would it?

I can't think of any good reason why not provided that you can jettison it quickly in an emergency. The Apollo spacecraft had a boost protective cover which was jettisoned in flight (at the same time as the LES I think although I could be misremembering). Not quite the same as a fairing but not too dissimilar either.

Share this post


Link to post
Share on other sites

I think this is on topic. There is a petition to name the first crewed dragon capsule Jebediah Kerman. Check it out: Petition Here

Share this post


Link to post
Share on other sites

Thought about a reusable second stage much smaller than the ITS...

The Raptor will feature autogenous tank pressurization, using both LOX and CH4 in coolant loops that vaporize into pressure-bearing spherical intertanks in the ITS, as shown here:

pressure-bearing_intertanks.png

The intertanks are tapped to pressurize the main liquid propellant tanks; they are also tapped to operate the hot-gas methane-oxygen RCS/OMS thrusters. Since these tanks are filled off coolant loops on the main engine, the total dV is limited.

Even though the Raptor will be able to downthrottle to 20%, that would still be far too powerful for landing a smaller reusable second stage, and the vacuum Raptor on a hypothetical reusable second stage would have really bad flow separation at sea level. However, if the RCS/OMS engines were sized large enough, and could compensate for altitude, then a reusable second stage could land propulsively on those, if there was enough dV. As an added bonus, it could land on its long axis rather than on its tail, allowing for better safety margins and simpler egress. A reusable second stage would need to have a biconic re-entry anyway, so it would already be strengthened to allow for this.

Putting everything together might be tricky, though. I'm not sure where the thrusters (or the landing legs/skids) could be placed that would still be protected from plasma during re-entry. The Shuttle had its landing gear fold up inside its heat shields, so that's always a possibility.

30 minutes ago, KSK said:

I can't think of any good reason why not provided that you can jettison it quickly in an emergency. The Apollo spacecraft had a boost protective cover which was jettisoned in flight (at the same time as the LES I think although I could be misremembering). Not quite the same as a fairing but not too dissimilar either.

As I noted above, the bigger problem is the size of a second-stage vehicle.

48 minutes ago, CatastrophicFailure said:

And only moderately more prone to explosions. :D

He has just recently started saying "excuse me" on a regular basis. And I do mean regular. As in, at least twice every minute.

Edited by sevenperforce
1 person likes this

Share this post


Link to post
Share on other sites
58 minutes ago, Brent Kerman said:

I think this is on topic. There is a petition to name the first crewed dragon capsule Jebediah Kerman. Check it out: Petition Here

Erm... perhaps that's not setting the most encouraging precedent...  :0.0:

 

1 hour ago, KSK said:

I can't think of any good reason why not provided that you can jettison it quickly in an emergency. The Apollo spacecraft had a boost protective cover which was jettisoned in flight (at the same time as the LES I think although I could be misremembering). Not quite the same as a fairing but not too dissimilar either.

Yes, the boost cover was integral to the LES. It's whole purpose was to protect the capsule from the LES

2 people like this

Share this post


Link to post
Share on other sites

Another thought on potential second-stage recovery, more near-term....

The difference between the expendable F9 first stage and the reusable F9 first stage is fairly minor, really. They use the exact same core design; the difference is that the reusable version has legs (with pneumatic systems) and grid fins bolted on.

I wonder if a similar process might be followed for the second stage. Same exact core design, but bolt on wing-like extensions (think ITS spaceship) with TPS wrapping around one side, to allow for biconic re-entry. They could add SuperDracos inside the wings for the landing burn.

S2_R.png

As depicted, the prop tanks (and pressurant tank) for the SuperDracos would be inside the bolt-on recovery sections. Not sure where the landing legs would go, though. If the base was stiffened enough, I suppose that landing legs could fold down from the top.

Share this post


Link to post
Share on other sites

That looks really heavy. Not sure you would have any worthwhile payload left.

Share this post


Link to post
Share on other sites
6 hours ago, sevenperforce said:

They don't make a fairing big enough for the entire second stage.

You seen the 500 series fairing? Goes around the centaur.

2 people like this

Share this post


Link to post
Share on other sites
46 minutes ago, DarthVader said:

You seen the 500 series fairing? Goes around the centaur.

That's an odd design decision. Why exactly is that? Also which engine has a nozzle extension which is also an interstage fairing that simply slides down into position when the second stage separates? Wasn't it Centaur too? I'm assuming doing that and then sliding it back up to use the Merlin as a sea level engine wouldn't work because vacuum engines operate at different thrust pressures or sth like that?

I have to say that I really liked the nose-first concept. The only problematic thing might be the CoM when the main tanks are empty. Did waaaay too many flips in KSP that way. How much the second stage Dracos + fuel would weigh?

Edited by Veeltch

Share this post


Link to post
Share on other sites
1 hour ago, Veeltch said:

 

I have to say that I really liked the nose-first concept. The only problematic thing might be the CoM when the main tanks are empty. Did waaaay too many flips in KSP that way. How much the second stage Dracos + fuel would weigh?

Remember that KSP CoMs move differently from IRL ones, and any fuel left over during reentry would shift towards the nose of the craft.

1 person likes this

Share this post


Link to post
Share on other sites
41 minutes ago, Mad Rocket Scientist said:

Remember that KSP CoMs move differently from IRL ones, and any fuel left over during reentry would shift towards the nose of the craft.

True, however it would not be much fuel left, they could however add fins to the back who extends after separation, this would also increase control. 
The idea of nose landing start to grow on me, you would need pop out engines for landing, combine this with the landing legs.
Could they used pressure feed engines? you don't need a lot of trust after all, think scaled down superdraco designed to run on RP1 and Ox, 
Benefit is no need to flip around, you don't need to change the main engine, short landing legs save weight.
Downside is more piping as you need to drain fuel and ox from top, might also affect pressurization. 

Share this post


Link to post
Share on other sites
12 hours ago, Veeltch said:

That's an odd design decision. Why exactly is that? Also which engine has a nozzle extension which is also an interstage fairing that simply slides down into position when the second stage separates? 

That'd be the DCSS, with a RL-10 B2.

1 person likes this

Share this post


Link to post
Share on other sites
9 hours ago, magnemoe said:

Could they used pressure feed engines? you don't need a lot of trust after all, think scaled down superdraco designed to run on RP1 and Ox, 
Benefit is no need to flip around, you don't need to change the main engine, short landing legs save weight.
Downside is more piping as you need to drain fuel and ox from top, might also affect pressurization. 

We can be fairly certain that they would not develop new kerolox landing thrusters; the SuperDracos are pressure-fed hypergolics which are massively different than a kerolox engine. If they were going to use main tank residuals, they would be more likely to dust off old Kestrels, though pressure-feeding would probably still be a problem. 

The main options are Dracos, SuperDracos, or cold gas thrusters, though the latter are unlikely due to their very, very low thrust. Note that the Dragon 2 will use differential throttling on its eight SuperDracos to control pitch and yaw (and possibly roll as well), but to have pitch and yaw, you need a minimum of three engines. You can get away with two if they each have at least one plane of gimbal...but, again, the Dracos and SuperDracos are not equipped with gimbal.

10 hours ago, magnemoe said:

True, however it would not be much fuel left, they could however add fins to the back who extends after separation, this would also increase control. 
The idea of nose landing start to grow on me, you would need pop out engines for landing, combine this with the landing legs.

Main problem: there's nowhere to put "pop out engines". You can't put them inside the stage, since its walls are its tanks. You can't put them outside the stage, since they would wreck the aerodynamic model and likely prevent LV qualification from going through. The only place would be inside the fairing, on top of the existing payload adapter but underneath the actual (new?) payload adapter, and the geometry doesn't seem to add up.

For feathering the stage during re-entry, however, it might be possible to use the same grid fins as the first stage, but with TPS wrapped around the edges. That way they could be edge-down during re-entry but turn to flat-face-down for the coast and landing.

12 hours ago, DarthVader said:

You seen the 500 series fairing? Goes around the centaur.

Ah, good catch. Although the Centaur is pressure-stabilized like the old Atlas tanks and so it makes a little more sense to protect it with a fairing. SpaceX certainly doesn't have a fairing as big as the 500. Wrapping a new fairing around an independently-flying stage intended for atmospheric re-entry (and a manned one, at that) seems problematic in a lot of ways; the larger the fairing, the harder it is to rapidly deploy, which is just a little bit important in a launch abort.

Share this post


Link to post
Share on other sites
On 4/18/2017 at 11:07 AM, Nibb31 said:

It's pretty clear that it flies inside a fairing.

Must be a pretty big fairing then...

 

(Sorry, poor lols on my part. :D)

But I've found in KSP the biggest problem is preventing flips in re-entry, or re-flipping for landing. So I may try an upside down second stage lander.

[Edit] Still the same problem if the fuel distribution changes the COG. But if I put the fuel/engines for landing at the top of the craft (bottom on re-entry) it may work.

Edited by Technical Ben

Share this post


Link to post
Share on other sites

Someone over on NSF pointed out that the second stage already uses cold gas thrusters for sole roll control, meaning there is sufficient roll authority to spin up the stage. Thus, a stock stage could be spin-stabilized for nose-first re-entry without any changes to stage design.

From the SpaceX Falcon 9 user manual:

payload_adapter.png

So they already swap out payload adapters based on payload mass. It would be fairly straightforward to have a "recovery-enabled payload adapter" which has spray-on or stick-on TPS added to it, though it might be difficult to protect the actual payload attachment points.

Finally, I noticed odd flaps around the engine area in this SpaceX CGI rendering:

flaps.jpg

These are not present on the current expendable S2. Could these conceivably be TPS flaps intended either for control or simply for feathering during entry...e.g., if spin-stabilization was not used?

SpaceX could test the initial recovery method on the FH inaugural flight using only spin-stabilization and a custom, TPS-equipped payload adapter. It would still ditch in the ocean at terminal velocity, like F9 S1 did on the CASSIOPE mission, but it would still provide a basic test of the primary recovery method.

Adding chutes would be the only way to achieve some sort of actual recovery without adding significant additional hardware. The second stage masses around 4 tonnes; chutes would only run you about 50 kg. I just don't know how much space they would take up; I don't think they could be placed around the engine.

Mockup of minimal modifications:

minimal_mods.png

It's so much smaller than the first stage that it could tip-over without breaking up, and tank buoyancy would keep it floating.

Edited by sevenperforce
mockup

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!


Register a new account

Sign in

Already have an account? Sign in here.


Sign In Now