SpaceX: First stage landed Satellites in orbit

[LURCH]

Even watching it live, it didn't look real. That thing just came screaming down out of the sky, blasting flames. Then the flames went out, and I thought it had malfunctioned and was going to crash. Then the engines re-ignited, and the vehicle remained visible all he way down to the tree-line, where it still looked to be dropping too fast.

But it dropped out of site and no fire ball erupted, so that seemed to have gone ok. While I was still wondering if it had landed in one piece, there was this deafening double sonic boom, which made everybody jump; very reminiscent of the shuttle. Then someone watching the video feed said, "they did it; it's down safely!". We all cheered just like the folks at launch control. Never seen anything like that.

 

[mheslep]

@mheslep: It is a bit better: payload has to go all the way to orbit, fuel for first stage return just has to get accelerated until the first stage engines cut off. That is a huge difference (~factor 5-10?).

Rocket equation applies stage by stage. Two stage to LEO is 16.7% non fuel mass, ie rocket and payload, total all stages, +/- a bit depending on fuel choice. Doesn't leave much for payload.
https://en.m.wikipedia.org/wiki/Tsiolkovsky_rocket_equation#Examples

I think single stage rocket-only to orbit is impossible with chemical fuels?

 

[mheslep]

Even watching it live, it didn't look real. ...

:) A couple decades hence, people may look back on the Apollo parachute landings in the ocean, and say, that's nuts, does look real.

 

[mfb]

Rocket equation applies stage by stage. Two stage to LEO is 16.7% non fuel mass, ie rocket and payload, total all stages, +/- a bit depending on fuel choice. Doesn't leave much for payload.
https://en.m.wikipedia.org/wiki/Tsiolkovsky_rocket_equation#Examples

I know - so what? The second stage doesn't care about additional fuel in the first stage. 1 kg of remaining fuel in the first stage is like 1 kg of structural material in the first stage: you just need the "payload" (total second stage+payload mass) to total mass factor of the first stage, not the payload to total mass ratio of the whole rocket.

I think single stage rocket-only to orbit is impossible with chemical fuels?

Or at least so impractical that no one ever did it.

 

[Monsterboy]

I think single stage rocket-only to orbit is impossible with chemical fuels?

Or at least so impractical that no one ever did it.

Skylon's space plane which is currently under development can be considered as a single stage vehicle right ? Well it's not a rocket
https://en.wikipedia.org/wiki/Skylon_( spacecraft )

 

[mfb]

I guess you can count the various ideas of nuclear propulsion as single-staged as well. There are concepts, yes, but nothing that left the ground so far.

 

[cjl]

It's not the fuel cost but the additional mass from additional fuel that is the issue. Payload mass is no more than single digit share of the total, so every additional kg of fuel (and tank and landing struts and ...) for boost back means a kg less of payload. The first step in this achievement was Spacex's breakthru reduction in vehicle mass (outer skin, turbo pump ,...), which then allowed fuel etc for a booster landing.

I don't know that I'd call it breakthrough - the first stage of the Falcon has a full mass to empty mass ratio of something like 20:1, which, while very good, is hardly unprecedented. The Atlas LV-3B from the 1960s had close to 50:1, for comparison, though to be perfectly fair with that comparison, it's worth noting that the 50:1 is after it had dropped off some of its engines (and if you compare empty but with all engines to fully fueled, it ends up closer to 23:1).

 

[mheslep]

Not a comparable payload on the old Atlas, trading payload for fuel. Atlas was a couple tons, I think including the entire capsule. Falcon payload is 13 tons, not including the fairing etc. Falcon 1st stg empty now includes landing struts and aero fins. Lookin at a modern fully 2 stg Atlas, empty to full 1st stg ratio seems to be around 13.

 

[Dotini]

I'm glad the space age has finally caught up to where model rocketry was many decades ago.

In my distant youth, I designed and constructed a 4 stage model rocket, successfully launched, recovered, reloaded, relaunched and again recovered all 4 stages within 30 minutes.

I'd very much like to see man on the Moon again or on Mars. But I'm not optimistic that it'll be accomplished in the foreseeable future.

 

[Monsterboy]

The actual goal is to land the rocket at the same launch pad from where it launched right ?

 

[mrspeedybob]

The actual goal is to land the rocket at the same launch pad from where it launched right ?

I'd be doubly awesome if they could land the second stage on top of it, so that all they'd have to do between launches is re-fuel, and put another payload on top.

 

[mheslep]

I'm glad the space age has finally caught up to where model rocketry was many decades ago

Vice versa, now model rocketry can attempt to catch up to reality and attempt controlled landing using propulsion. I'm unaware of any thrust control used in model rocketry, but it would be required as in the real thing. Guidance on ascent makes use of an innately stable aerodynamic vehicle (fins that place the CP well aft of the CG). Modelers will have to raise their game considerably to match this.

 

[mheslep]

I know - so what? The second stage doesn't care about additional fuel in the first stage. 1 kg of remaining fuel in the first stage is like 1 kg of structural material in the first stage: you just need the "payload" (total second stage+payload mass) to total mass factor of the first stage, not the payload to total mass ratio of the whole rocket...

Yes, sorry, I missed your point in your earlier post.

 

[mfb]

The actual goal is to land the rocket at the same launch pad from where it launched right ?

The launch pad needs support structures that would be in the way for a controlled landing, so I doubt they will use the same pad ever. It's not that hard to move a rocket by a few kilometers, and you need access for some maintenance and putting the second stage on top anyway.

 

[cjl]

Not a comparable payload on the old Atlas, trading payload for fuel. Atlas was a couple tons, I think including the entire capsule. Falcon payload is 13 tons, not including the fairing etc. Falcon 1st stg empty now includes landing struts and aero fins. Lookin at a modern fully 2 stg Atlas, empty to full 1st stg ratio seems to be around 13.

Yes, because they decided balloon tanks are too much of a headache for the modern Atlas, so its structural fraction is worse. There are also quite a few other tradeoffs involved - I'd bet the modern staged combustion Russian engines the modern Atlas uses are quite a bit heavier than the old Atlas engines, for example, though they make up for that with their extremely high efficiency. As for the payload, I'm comparing the first stage's empty mass to its fully fueled mass - payload doesn't come into this at all. You have a valid point about the landing legs and aero fins though - I'm not sure if the number I found included those, and if so, how much those are contributing to the empty mass.

 

[enorbet]

I'm glad the space age has finally caught up to where model rocketry was many decades ago.

In my distant youth, I designed and constructed a 4 stage model rocket, successfully launched, recovered, reloaded, relaunched and again recovered all 4 stages within 30 minutes.

I'd very much like to see man on the Moon again or on Mars. But I'm not optimistic that it'll be accomplished in the foreseeable future.

Not to take anything away from Model (paper and balsa wood) or even Amateur (Stainless Steel and/or Carbon Fiber) Rocketry achievements but I think your first statement is rather hyperbolic :) it isn't even just a problem with scaling ie: Square-Cube Law but rather that the comparison is actually more Apples-to-Oranges, given that almost no Model rockets and very few Amateur rockets carry any payload at all excepting the body of the rocket which, in the case of Model rockets, doesn't even need to exist since it is possible to glue balsa fins directly on "the engine" as well as an (optional) nose cone and it will fly just fine.

The body is commonly, aside from appearance, just an aerodynamic housing for the parachute. In those few with actual payloads, eggs and cameras are the most common payloads of Model and Amateur rockets and even in those most advanced cases the rocket to payload ratio is extremely high, making parachute-only landings possible and relatively safe and easy.

This doesn't even address the vast differences in Mass and complexity once we leave the realm of "burn once" solid fueled devices, nor even the need for precision in all systems, not to mention guidance which is entirely static on both model rockets and amateur. Even recovery parachute deployment is left to a timed slow burn built-in the engine at the factory in the case of Models and little more than a mercury switch activated by Brennschluss in Amateur rockets. Nothing is optimized nor controllable beyond lighting the fuse. Timing is left to "good enough to work" with usually zero flexibility. All of this makes for a vastly reduced combination of mass and complexity so that no serious comparisons are possible, certainly of no value nor concern.

I do agree that putting men on Mars is likely a very long way off in time, but I'm betting Men on the Moon will occur within 10-15 years at the most, but neither has anything to do with any non-existent lag behind modelers.

 

[Monsterboy]

I'd be doubly awesome if they could land the second stage on top of it, so that all they'd have to do between launches is re-fuel, and put another payload on top.

Lol ,that will be too risky what if the first stage lands fine and the second stage crashes on top of it ?? it will be better if they land just a few hundred metres from each other near the same launch pad from where they were launched, because Elon said (in TED Talks) that the goal was to reuse the rocket within a matter of hours.

 

[Xu Shuang]

Aye. First time in history, right, from a full orbital launch?

e

Only the first Stage rocket is recovered,which could cut the expense by half, at most.

 

[cjl]

Only the first Stage rocket is recovered,which could cut the expense by half, at most.

Why do you assume the first stage is only half the cost? It contains 9/10 of the engines, and something like 75-80% of the mass. I seem to remember hearing an estimate that the first stage was more than 75% of the overall cost of the launch vehicle.

 

[Blank_Stare]

Stage separation happened at 6000 km/h (and 77 km height), satellite deployment at 26000 km/h. That is 23%.
Full launch video
Vertical velocity seems to be more than 1km/s at that point. A very steep launch profile, but one that helps to get the first stage back to the launch pad.

Thank you for that link - very nice to watch.

 

[mfb]

The first stage is by far the most expensive part. You cannot buy them individually for obvious reasons, so there is no official price tag, but 75% or more sound realistic.
A factor of 4 won't give us all a nice holiday trip in an orbital hotel, but it is a huge step in the right direction.

 

[mheslep]

The first stage is by far the most expensive part. You cannot buy them individually for obvious reasons, so there is no official price tag, but 75% or more sound realistic.
A factor of 4 won't give us all a nice holiday trip in an orbital hotel, but it is a huge step in the right direction.

I expect the resulting increased launch rate will also reduce cost beyond that afforded by reuse of the stage.

 

[mfb]

It should. SpaceX has a really crowded launch schedule, 30 launches next year. Some of them will get moved to 2017 for sure (and some of the 2017 launches to 2018), but even 15-20 launches would be a lot.

 

[Xu Shuang]

Why do you assume the first stage is only half the cost? It contains 9/10 of the engines, and something like 75-80% of the mass. I seem to remember hearing an estimate that the first stage was more than 75% of the overall cost of the launch vehicle.

Based on the experience of space shuttles, recovering the first stage doesn't mean the cost of the first stage is gone. The first stage would still need serious renovation before reuse. For space shuttles, the engine need to be replaced every three missions. For the rocket, the renovation cost would be less, but would still be far from an ideal reuse.

 

[cjl]

Based on the experience of space shuttles, recovering the first stage doesn't mean the cost of the first stage is gone. The first stage would still need serious renovation before reuse. For space shuttles, the engine need to be replaced every three missions. For the rocket, the renovation cost would be less, but would still be far from an ideal reuse.

The space shuttles and this share very little though - the engine design is completely different, the resuse model is completely different, the fuel is completely different... It remains to be seen how much can be saved through reuse, but comparing this to the shuttle seems somewhat irrelevant to me.

 

[mheslep]

Based on the experience of space shuttles, recovering the first stage doesn't mean the cost of the first stage is gone...

Not gone, but in the same cost model as commercial aircraft as opposed to one and done.

 

[HyperTechno]

A really great and successful attempt. This will benefit the future space explorations. Less space pollution and less wastage of materials and money!

 

[LURCH]

It's my understanding that the real savings here is not the reuse of the stage (by witch I mean that the stage was going going to be reused in any case). The big cost reduction is the fact that they don't have to go out to sea in a ship to retrieve it.

Don't know how much that cost, but I know it isn't cheap.

 

[mfb]

A really great and successful attempt. This will benefit the future space explorations. Less space pollution and less wastage of materials and money!

More junk in space, at least in the short run. First stages don't stay in space with any current rocket, so returning them does not help in that point. Cheaper launches mean more launches means more stuff in space.

It's my understanding that the real savings here is not the reuse of the stage (by witch I mean that the stage was going going to be reused in any case). The big cost reduction is the fact that they don't have to go out to sea in a ship to retrieve it.

No, the cost reduction is the actual re-use of the first stage (which is not demonstrated yet, but I hope we'll see it in the near future). Collecting waste (if done at all) would be cheap.

 

[LURCH]

Yes, I understand that reusable rockets are a big cost-savings, but this is far from being the first reusable rocket. Reusable rockets have been around a long time. What makes this rocket different is that it doesn't have to be fished out of the ocean. I'm just wondering if the cost of extra fuel to make the first stage come back and land is really going to end up being a significant savings, bearing in mind that the stage would be reusable whether it lands near the launch pad or in the ocean. And wether that savings will be immediate, or will it come in the form of bigger up-front costs that will be regained over time?

 

[mfb]

What makes this rocket different is that it doesn't have to be fished out of the ocean.

The Shuttle boosters needed months of "repair" - a bit cheaper than starting from scratch, but far away from what SpaceX wants to do: launch, land, and be ready launch again possibly within hours (currently weeks would be sufficient, fuller launch schedules can change that).

The size of the rocket is fixed for Falcon 9. If the payload mass allows it, they will continue to land on land, it has a higher success rate and saves some trouble with the drone ship. If the payload is too heavy, the drone ship is an option.

 

[HyperTechno]

launch, land, and be ready launch again possibly within hours (currently weeks would be sufficient, fuller launch schedules can change that).

Why don't they attempt some big Space shuttles that are capable of taking most of the things like supplies, satellites to space. NASA retired the space shuttles and I've heard that they did that because of the Colombia disaster... . But anyway, I think attempting a new shuttle project will help to lower the addition of Space Junk and also will save the cost...
Because although the rocket boosters come back, still some items are left in the space in the modern Rockets.
Whatever the problems with the former shuttles, I think the modern technology can come over them to make much safer and effective Space Shuttles.

 

[mfb]

The space shuttle was designed to lower costs, but various technical and management issues made it much more expensive than planned. The Columbia disaster contributed to the retirement, but it was never a cheap system.
The Falcon Heavy will have about twice the payload mass of the Space Shuttles.

Because although the rocket boosters come back, still some items are left in the space in the modern Rockets.

That is not different for SpaceX. Cheaper access to space can make special debris collection satellites more interesting.

 

[cjl]

Why don't they attempt some big Space shuttles that are capable of taking most of the things like supplies, satellites to space. NASA retired the space shuttles and I've heard that they did that because of the Colombia disaster... . But anyway, I think attempting a new shuttle project will help to lower the addition of Space Junk and also will save the cost...
Because although the rocket boosters come back, still some items are left in the space in the modern Rockets.
Whatever the problems with the former shuttles, I think the modern technology can come over them to make much safer and effective Space Shuttles.

Because wings are large, heavy objects that have to be strengthened, heat-shielded, and carried along for the entire flight, even though they are only useful during the last 5 minutes. A shuttle looks really nice on the back of a napkin, but in practice, at least with current achievable payload mass fractions, you end up wasting a huge amount of fuel and effort carrying around something that's much heavier than needed.

 

[mheslep]

wings are large, heavy objects that have to be strengthened, heat-shielded, and carried along for the entire flight, even though they are only useful during the last 5 minutes.

True of the Shuttle wings but perhaps it need not be so. Some cruise missiles deploy wings in flight and most (all?) carrier air craft have fold-able wings. Stowed wings need not be heat shielded nor withstand high mach numbers nor drag the vehicle air frame on ascent, so weight comes down.

http://enu.kz/repository/2009/AIAA-2009-1291.pdf

While the Falcon Heavy and other vehicles will no doubt replace the shuttle's lift capacity, nothing yet comes close to the Shuttle's capacity for returning heavy payload to the surface: seven astronauts and all of their life support which can be reused, plus a few satellites in the trunk.