A helicopter will try to catch a rocket booster mid-air | Hacker News Reader

A helicopter will try to catch a rocket booster mid-air

spectrum.ieee.org

122 pointstakiwatanga79 comments

They have a demo video showing a helicopter catching a booster dropped from a second helicopter:

https://www.youtube.com/watch?v=N3CWGDhkmbs

(from https://www.rocketlabusa.com/launch/electron/ )

The parachuting booster falls at 10 meters per second from 6000 meters, so they've got a pretty tight window.

The helicopter has a ceiling of 4300 meters and can cover about 3 km a minute, so you've got a couple minutes after the chute deploys to get to the closest safe distance when the booster is still above the helicopter and then about 5 minutes to catch it once the helicopter is above it.

Many years ago I was at Dugway Proving Ground when NASA was supposed to catch the Genesis Space Probe under parachute with "hollywood stunt pilots" flying A-Star helicopters with long probes mounted on the front, to hook the parachute in mid-air.

It all would have worked out swimmingly if the parachute on the Genesis would have opened, but an installation error caused it not to and for the probe to smash into the ground, leaving some very confused and disappointed helicopter pilots, among others.

Space is hard.

Hey, I was there, too! It was a long way to go to end up watching the catch attempt on monitors in a hangar.

If I remember correctly, the problem was that the deceleration sensors were drawn upside down.

The original phrasing of Murphy's law was: "every component than can be installed backward, eventually will be".

The Russian adaptation would have to be even broader:

https://twitter.com/djsnm/status/1039553531001241601

"hollywood stunt pilots" was clearly the best part of that entire story; like you could write a novel or a screenplay using that and adding "space probe" and "catching" to it.

I suspect that this will only be a viable procedure until the inevitable accident that causes a helicopter crash, then it will be deemed too risky for regular use (unless the helicopter can be unmanned)

Something very similar (capturing space capsules) was done regularly from the 1960s to the 1980s, so it's not like there isn't precedent for this.

But that was in military context, with higher risk tolerance to loss of human life. (for getting intel, way more dangerous methods are applied all the time)

While you are probably technically right, I think you are over estimating the risks involved. The booster will be under a parachute, travelling relatively slowly, and there will clearly be many safety precautions and features involved. They will certainly have a stringent check list before proceeding with the attempt as well as some sort of fail safe cutting of the lies if something goes wrong.

I would expect the chance of a serious accident to be very low.

Also keep in mind these sort of mid air captures were well practiced by the US during the Cold War to capture returning photographic film from spy satellites. Although that was with airplanes not helicopters. A variation of it is actually shown at the end of James Bond Thunderball where he and the girl are rescued from a life raft via a balloon and capturing plane.

Low as it may be, it seems like an unreasonable risk, given the recent advancements in pilotless (and remotely piloted) aircraft.

Helicopters bring more risks than airplanes. Helicopters with external attachments are notoriously risky (for aviation standards). Helicopters with external attachments that bring momentum independently of the main vessel are the kind of thing that looks way too risky.

An airplane would probably cope much better. And even then, the fact that the military do something is not a good reason to expect it to be viable for civilian use. Military applications tend to accept much more risks.

>An airplane would probably cope much better.

LOL. Yeah sure, so the plan is to have something traveling at 800kph somehow intercept a falling rocket stage, catching it in a web or whatever and start dragging it along and somehow land safely afterwards?

Thanks man, you made my day :D

C-130s (like the planes that were used for retrieving objects dropped from satellites) are fine flying at 200kph, no need to max out their speed.

To their point, I'm not sure how well a carefully controlled slow descent and catch interplays with an object that can never be in place, in fact, it needs to be at 200 kph. Sounds much less safe.

It works great. This story isn’t notable for the recovery method. It is notable because of what is being recovered (a reusable rocket booster).

No, it doesn't. Lol.

From wikipedia, it can land on as low as 120km/h. (That thing can be really slow, it's impressive.)

Still, I expect an empty second stage rocket to weight little enough that one can get by with a smaller plane, that can fly slowly due to its little weight, instead of sheer engineering feat.

The first mid-air recovery of CORONA spy satellite film canisters by a C-119 Flying Boxcar fixed-wing aircraft was performed in 1960. This is a well understood capability.

https://en.m.wikipedia.org/wiki/CORONA_(satellite)

https://en.m.wikipedia.org/wiki/Discoverer_14

And even earlier for (much larger) jet-powered target drones: 1955.

There is absolutely NO comparison, in terms of mass, momentum and similar related forces, between a "film canister" and the first stage of a rocket.

But common sense is quite uncommon nowadays.

> LOL. Yeah sure,

> But common sense is quite uncommon nowadays.

I see on your page you say "I take pride on behaving righteously and honestly". Don't forget also:

Be kind. Don't be snarky. Have curious conversation; don't cross-examine. Please don't fulminate. Please don't sneer, including at the rest of the community. https://news.ycombinator.com/newsguidelines.html

Yes. It's not a new thing.

The Wikipedia article even has pictures for you https://en.wikipedia.org/wiki/Mid-air_retrieval

https://xkcd.com/1053/

Remember that they've already been practising this for months - it's not a first time thing - by now they likely know and understand the risks well

(Also NZ is full of helicopter pilots who work doing "deer recovery", snatching animals with shotgun-nets, hanging them under helos and pulling them off of near vertical mountain ridges - grabbing something under a chute is likely easy in comparison)

The variation is https://en.wikipedia.org/wiki/Fulton_surface-to-air_recovery...

Which also plays a major role in Metal Gear Solid V (and MGS: Peacewalker)

I can’t find its empty weight online easily, but this booster is quite a bit heavier than these film canisters were. I would be concerned about the impact catching it would have on the helicopter.

I guess the hook they use for catching it must be hanging from a somewhat line that deforms on impact, becoming longer while absorbing lots of energy. You don’t want this behaving like a heavy bungee jumper under your helicopter.

They've caught multiple mockups that were dropped.

I have friends in forestry, and their industry routinely uses helicopters, despite the risk, for a much lower ROI. Below are some videos of a christmas tree farm and a remote logging operation. I can't imagine that what rocket lab is attempting will be anything short of 10-100x safer.

https://www.youtube.com/watch?v=08K_aEajzNA

https://www.youtube.com/watch?v=kin7cxnyM1M

Power-line work on live transmission lines always seems incredibly bonkers.

https://www.youtube.com/watch?v=DPNK7bc2qvM

https://www.youtube.com/watch?v=9YmFHAFYwmY

Let's fly a massive chainsaw beside a powerline. That'll be safe:

https://www.youtube.com/watch?v=Mfz1YrpMbBg

The more you investigate industries the more solutions you find that were obviously designed by five year old boys.

I'll just use a CHAINSAW on a HELICOPTER!

How about helicopters lifting things from the street to the roof of a skyscraper? With the spinning blades mere feet from giant windows with people on the other side?

https://www.youtube.com/watch?v=AqnXj4oc3WY

(Look at around 12:30 for the most extreme)

I saw this kind of stuff multiple times when I lived in a high-rise. It's surreal to go out on your balcony, look down, and see a flying helicopter.

Reminds me of the chase scene in "The World Is Not Enough"

Forestry is a fairly low profile blue collar industry that doesn't get much mind share among the white collar people who think they're experts in how every industrial facility should run. You have the luxury of actually being able to make decisions by the numbers.

When you go into space numbers unfortunately tend to have to take a back seat to optics.

Someone crashes a log truck and nobody cares. Someone crashes a helicopter doing "space stuff" and suddenly every jerk who feels slighted that you didn't divert enough resources from your primary task (space!) to pander to their issue (your team isn't divers enough, your facility isn't environmentally friendly enough, your company vehicles aren't all EVs, etc, etc) along the way is happy to tell the news reporter or the Youtube head how you "have a history of playing fast and loose" or whatever. And then all the vultures who want to be seen "doing something" descend...

In those farming/logging videos, the helicopter is picking up stationary objects and depositing them in a desired location. I have trouble imagining that catching a moving object would be less dangerous, except to the extent that the pilot's job is only to catch a single thing that day, not move dozens or hundreds of individual objects.

(Those loggers though in the second video seem like they're standing awfully close.)

Both are very hazardous under different risk models.

There's a concept in flying stuff that you always want to be "three mistakes high" (I think this is credited to Gene Gottschalk although I have no idea if he was the true origin - it's taken a life of its own in many communities). By that logic, the Christmas tree pilot is at a very sub-optimal altitude - 0.75+ mistakes high, but still high enough that they're unlikely to make it out in the event of a mistake or catastrophic failure.

The retrieval helicopter is presumably several mistakes higher and more likely to recover from simple mistakes or equipment failure, but runs the risk of being smacked by a flying object.

Neither are safe, but I think there are mitigating factors to the rocket collection that aren't present in the Christmas tree video. I think they're closer to even risk-wise. If I were a helicopter pilot, I'm not sure I would want either job!

Yes, the target will be a moving object, but its motion will be steady and predictable. The helicopter and booster will be the only two objects in the area, and capture should be slow and steady when viewed from the reference frame of the copter that has matched velocity. Aerial refuelings look crazy from the ground but easy but from the pilot's point of view.

https://youtu.be/sL5MxCwkLJQ?t=94

How cheap must fuel be? And helicopter maintenance / depreciation hours per flight hour? How much does a christmas tree from that farm cost?

I wonder if they’re using a steerable parachute to put it on a predictable heading. In the rocketry hobby we use the drogue/main deployment to keep from having to walk so far to collect a rocket. Naturally, someone put an acrobatic parachute, gps, microcontroller, and some actuators in an airframe to fly a model rocket back to the launch rail. It worked pretty well. https://youtu.be/4ac-VFPAqIo

They already have a parachute on the booster. Why not steer the parachute and land on land?

The US military has been using automatically guided steerable parachutes for over a decade.[1] The current JPADS system has both GPS and visual guidance, so they can drop a load from a high altitude and land on target. There's a commercial version.[2] Maybe land on a target of crushable cardboard.

[1] https://www.youtube.com/watch?v=Q_CFv2MT7gM

[2] https://www.youtube.com/watch?v=2A3PfDfzYEM

probably due to the horizontal distance it would have to traverse to get back to land (and uncontrollable factors that would limit that, e.g. wind magnitude and direction during launch). your sources don't give an overview of how far those parachutes can glide, but it feels like they are deployed relatively close to their intended touchdown point.

The delicate rockets engines would likely be damaged

The rocket is hundreds of kilometers away from land at that moment.

1. Constraining the first stage to return over land would massively impact payload. This would be even worse than a Falcon 9 RTLS, because at least with that it can do a boostback, so the 2nd stage is still put on a relatively flat trajectory, just with earlier stage separation.

2. SpaceX tried using steerable parachutes for fairing recovery. Turns out, accurate enough to hit a small clearing for air-delivering supplies still has enough error that if you want to land it on some soft target, that target has to be very large. Larger than you think. The accuracy of GPS isn't the problem; parachutes are difficult to control with only a few degrees of freedom in control and are at the mercy of the wind.

3. A "target of crushable cardboard" absolutely wouldn't work. Since Electron's first stage is so light, I could believe some sort of large net, elevated above the ground could work. Probably cable-supported, with some sort of buffer on the cables to bring the net to a stop after the rocket lands on it. But that would be big and expensive.

4. A few hours of helicopter time is actually pretty cheap, especially compared to the alternatives. And catching things with a helicopter may not be common, but it is a proven technique with plenty of history behind it. And there's no shortage of very, very capable helicopter pilots able to accomplish such a feat.

I could be wrong, but I though SpaceX catches its entire rocket (all stages) now with rafts/boats, doesn't it? What does this add over that already-implemented system?

Wouldn't blimps be a far better tech to keep the net aloft?

Maybe they're afraid of Blue Origin? BO has a patent that covers "Sea landing of space launch vehicles and associated systems and methods"[0].

Of course, BO sued SpaceX and lost, so I'm not sure that they could win against Rocket Labs.

[0]https://patents.google.com/patent/US8678321B2/en

SpaceX's first stage lands itself, either on a droneship or on a landing pad near the launch site. The payload fairings splash down in the ocean, and get fished up for reuse. The second stage is not recovered.

Rocket lab just has a different approach to the same problem.

For some mission profiles, SpaceX boosters land right back where they took off. Neat as can be.

Here's a photo capturing launch and landing at Cape Canaveral in the same view.

https://en.wikipedia.org/wiki/Landing_Zones_1_and_2#/media/F...

Well, they return to a landing pad within a few hundred yards of where they took off. A difference worth pointing out because the plan for their next generation rocket is to actually return directly to the launch site.

Peter Beck gives great interviews on YouTube. About this, he said that helicopters are much, much cheaper compared to doing anything with boats. Rocket Lab's rocket is small enough that a helicopter can handle it, SpaceX's first stage is just too big.

Blimps don't really exist, there's 25 of them in the world. You can't just go out and get a blimp and operate it the way you can a helicopter.

I understand the low number of blimps, but it's not complicated technology-wise, and we're talking about a space company.

Let me rephrase from blimp: How about balloons? Just use more.

The failure situation of helicopters getting hit by the booster, snagging on the net, running into each other, etc seem all way worse that if blimps were doing the work. Although maybe if you had drone style helicopters it might be better, but like you said with blimps, do those exist in retail?

> I though SpaceX catches its entire rocket (all stages) now with rafts/boats, doesn't it?

SpaceX doesn't catch anything at the moment.

The first stage lands itself either at the launch site or on the autonomous barge at sea.

The fairings for the second stage get pulled out of the ocean by ship after they splash down. They used to try to catch these and that's what you're thinking of but they weren't that successful at it. I believe they redesigned the fairings to be okay spending a short amount of time in salt water and they seem to be having a pretty good success rate for this.

The second stage of the Falcon burns up in the atmosphere. Their Starship project is attempting to fix this.

The advantage of this approach for Rocket Lab is that they'll be able to re-use the first stage. At the moment SpaceX is the only one doing that and it's why they have such a commanding position in the market. I haven't seen an explanation for why (I'm sure it's out there, I just haven't seen it) but my guess is that the Electron is a much smaller rocket than the Falcon and they can't spare the lift capacity to propulsively land the vehicle.

Also there should be a weight/fuel reduction for not having to hold enough fuel to land itself and every bit counts. Along with not having to worry about igniting/firing your rocket engines a second time in a flight which is reduced complexity and also allows for solid booster recovery.

Indeed.

Reusable SpaceX rockets have 30% small payload compared to non-reusable ones, as they have to carry extra fuel for landing.

Catching the rocket instead of landing it could be significantly more efficient as you wouldn't have to carry much more weight except for the parachute.

You would also have to build your rocket such that it can survive the shock of braking via parachute. That eats at least some of the weight savings.

This isn't a 5-layer cake we're talking about here. A structure that can survive being caught between a payload on one end and a rocket motor on the other is going already have the strength you need in most of the places you need it in order to hang from a parachute. The hard part is going to be attachment point real-estate since the most logical choice is going to have it fighting for space with rocket motor bits.

"The second stage of the Falcon burns up in the atmosphere. Their Starship project is attempting to fix this."

Just in case: Starship is a whole new rocket, not just an evolutionary upgrade of extant Falcon 9 to full reusability.

Blimps and dirigibles are the solution for sure. Love those things on principle.

It means the rocket doesn't have to reserve fuel for a landing burn, and has more leeway in how it positions itself after re-entry, since the helicopter can move at least a bit to intercept. (NB SpaceX Falcon 9 boosters are too large to be snagged in midair by any extant helicopter -- and conversely, RocketLab has already announced that they'll be attempting SpaceX-style propulsive landing for their upcoming, much larger Neutron rocket.)

They don't recover stage two. That's a much different problem from recovering stage one, which has a ballistic trajectory; stage two goes into orbit.

This is a different company (Rocket Labs) so they wouldn't get to reuse SpaceX's capture methods. This method appears like it would allow them to use commodity helicopters instead of having to develop and build their own drone ship tech, which has the additional hassle of having to maintain a boat and have a dock they can use to haul the rocket. I'm guessing this is for their "Small Launch" offering so the heli option makes sense at that weight.

> I could be wrong, but I though SpaceX catches its entire rocket (all stages) now with rafts/boats, doesn't it?

Only some Falcon 9 launches recover the first stage. For performance reasons sometimes the booster burns all fuel and crashes into the ocean. The second stage has never been recovered and no attempt has ever been made. Early concepts may have mentioned it but I don’t believe the capability even exists on current Falcon 9s.

Starship is an entirely different rocket which has never been launched from a booster nor recovered from orbit. That is the eventual goal but SpaceX is far from achieving it for anything approaching “all” launches.

> Only some Falcon 9 launches recover the first stage

Almost all boosters are are recovered.

Flights that need enough acceleration to make the landing impossible are extremely rare. Falcon 9 already provides more payload capacity than most sats need.

I think some upcoming Falcon Heavy launches will expend the main booster though.

If we are going to argue semantics the only thing that matters in this context is that less than all boosters attempt recovery.

Peter Beck (Rocket Lab CEO) has explained in a few interviews that maintaining a fleet of boats is incredibly expensive, and that this cost is one of the major reasons why they didn't go this route. Operating helicopters is much cheaper in comparison.

He has quoted actual numbers in the past, such as in this December 2021 interview (https://youtu.be/gcuOSXjevGs?t=751): "Do you have any idea what it costs to operate a ship? It's way way cheaper for Electron to fly it with a helicopter than it is to put a ship out there for a couple of days. It's just ridiculous. Marine assets are SO expensive. […] The Bell 429 that we operate is like $3,000 an hour. […] It's a 2.5, 3 hours flight. […] It's like $60-70,000 for the ship just to sit in the port! Not even going anywhere, it's $60,000 a day. And that's just a tiny little ship."

> It's like $60-70,000 for the ship just to sit in the port!

This sounds out of context. Maybe a speciality ship (stabilizers? crane?), capable of dragging/lifting a 1000-ton payload, in harsher weather, and can loiter if required.

If you build your own 2000-ton ship (excluding r&d, construction, depreciation) what would be the daily operating cost (crew/fuel/insurance) etc?

Hard to not wonder about success of combining 2 least robust technologies. All the luck to them. Who knows where the true disruption happens.

Wonder no more, this was proven to work over 60 years ago.

> As long ago as 1960, the U.S. Air Force snagged a returning capsule from a mission called Discoverer 14

That was a capsule; look at the size of this relative to the aircraft — https://en.wikipedia.org/wiki/Discoverer_14#/media/File:Fair...

A first-stage booster is order(s?) of magnitude larger.

They have tested catching a dropped mockup version multiple times.

Has nobody thought to slap a set of retractable wings on them, and turn them into remote controlled gliders?

That's completely over-engineered. You just need inflatable floats and then the helicopter can pick the booster up within minutes to prevent salt water corrosion.

They have done recoveries from the ocean, so they have rejected that option.

“The first stage burns out after the first 70 km”. There’s very little atmosphere there, so it would effectively free fall for a while first, and then would have to start gliding.

You can’t rapidly get from a fast free fall (almost vertical) to gliding (almost horizontal), or your wings will break of. That means you either need something to rapidly (but not too rapidly) decrease vertical speed, or you need lots of height to make a slow turn (this thing will be falling at thousands of km/hour before it reaches denser atmosphere). I guess “lots of height” is a bit more than 70km for realistically strong wings.

So, you need something to decrease vertical speed. A parachute is the best solution we have for that. If you have that, why add wings, too?

If you launch to orbit, there is a gliding solution that will work: wait for atmospheric drag to slowly bring the booster down to denser atmosphere, but these boosters don’t get into orbit, and even if they did, it would take way too long.

> I guess “lots of height” is a bit more than 70km for realistically strong wings.

A drop test of Dream Chaser prototype was done a few years ago from a helicopter, definitely not 70 km of altitude. The prototype successfully landed onto a landing strip.

I maybe mistaken, but I don’t see how that’s relevant. Dream chaser is designed to return from orbit. These boosters won’t reach anything like orbit, and will have insufficient horizontal speed to start gliding.

Also, if you want to glide these boosters to earth, the challenge is to get them into more dense atmosphere with a low vertical speed. Once you’re there, it’s ‘easy’.

A test dropping them from a helicopter doesn’t test the ability to do that at all; it tests the ability to land after you’ve done that.

People have thought of it. I recall a Soviet design that would have put wings on the strap-on boosters.

Wings are heavy, a parachute is lighter. Every pound added is many pounds less payload.

Not with me in it.

Thanks for clarifying; When I first saw the headline I wasn't sure whether you'd be inside or not.

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