It would appear that the first stage operational reusability is happening for multiple companies in the near future. The next step seems to be fairings and second stages coming back for more employment. It seems to me that there may be a possibility to use one to assist the other if there is enough payload margin. I am suggesting that the fairing be kept with the second stage all the way into LEO, or possibly even into GTO.
The payload fairings on most vehicles seem to be more expensive and robust that I had been aware of even a few weeks ago. I am going to suggest incorporating a heat shield into the fairing and using it to protect the second stage through reentry. It would appear that the mass of fairing and second stage would have a fluffy enough reentry profile that the heat shielding material would be a fairly minor mass hit compared to those on vehicles with higher density. The main mass hit would be that of carrying the fairing through the whole mission rather than the normal jettison at low enough dynamic pressure.
                                             At payload separation, two arms on the second stage lift the one piece fairing off of the payload exposing it to space. That is cartoon 1 on the left with the arms in green. The arms flip the fairing around and pull it up over the engine and tanks as in cartoon 2. At reentry the stage is fully enclosed in the fairing with the engine mass forward in the pointy end as in cartoon 3. If it can be done this way, the second stage would see very little thermal stress during reentry and has the possibility of gas-n-go seriously enhanced.
Bonus points with the arms would be if they could be used for deploying solar panels and antennas for the spacecraft before deployment saving a bit of risk and complexity. More bonus points if the arms could also be used to deploy parachutes or other recovery gear at the lower altitudes.
johnhare
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Fairing separation happens after it’s done its primary job. You’re proposing its secondary job be to protect the engines but does it have a better use? Use the fairing to turn the 2nd stage into a shuttlecock? Instead of 2 halves divide it into 3 or more pieces hinged at their base to increase drag which would be much easier to deploy and the engines could still be used after slowing to terminal velocity.
The problem with my suggestion is the body might have more twisting force than the feathers/fairing can counteract?
The way I see it, your shuttlecock leaves the second stage exposed to mach 25+ reentry heating when the F9 already has issues on occasion with much lower velocities. And a one piece structure has the potential to be lighter than multiple sections.
I guess the good news is your one piece deployment is out of the atmo. and in freefall. Bad news is it might interfere with payload deployment? It would seem to be worth looking into.
My understanding is the payload fairing is typically shed once sufficient altitude is gained for aerodynamic drag to be negligible, well before orbit. Depending on launch trajectory this might happen before first stage separation. Carrying the fairing all the way to orbit reduces payload by a large fraction of fairing mass.
The fairing is normally jettisoned as you say. This is a post about a possible recovery method that would cost some payload. The question is whether it would work, and if it would ha worth the effort.
A fairing might more suitable to act as a heat shield if it’s more blunt. This would increase drag, but it’s possible to use an extended aerospike to reduce drag again (this is done with an extensible aerospike on SLBMs, due to space constraints). In this application I imagine the aerospike would start extended and then be jettisoned.
FYI: payload fairing jettison is typically triggered based on aeroheating threshold, not dynamic pressure, which is why it typically hangs around a bit longer than you’d think (rho*V^3 tapers off a lot slower than rho*V^2).
I love the idea of reusable second stages but unless the vehicle has excess capability that comes at a 1:1 cost to payload. Bring on the BFR’s!
-philip
Upper stage recovery might be better done with a magnetoshell system as Jon has noted elsewhere:
http://www.altius-space.com/icymi-magnetoshell-vacuum-chamber-test-pictures/
This ought to be of interest to DARPA, a modest program that could have very high payoff but is currently uncertain.
I just found that MSNW got a phase II SBIR last year , I hope they get good results.
https://www.nasa.gov/feature/magnetoshell-aerocapture-for-manned-missions-and-planetary-deep-space-orbiters
Doug,
MSNW is playing things cautiously, and doesn’t want to be accused of overhyping the MAC technology. They’re working on a NIAC Phase II to try and mature the technology and do some subscale tests to better understand the physics. While right now they’re not willing to say they’re confident MAC will work for aeroentry work, they are planning to do some plasma/atmosphere interaction tests (firing plasma balls from their thrusters into their vacuum chambers with vacuum levels and gas compositions mimicking various atmospheres and altitudes, including Earth atmosphere. So hopefully by next year we’ll have a better idea of if MAC is likely to work well at slower speeds and lower altitudes.
If it does, it would be ideal for use with LOX/LH2 upper stages like ACES that have lots of on-board power available… 🙂
Even if it only works for aerocapture/aerobraking it’s already hugely enabling, but I’m not giving up on my crazy hope it can help with aeroentry.
~Jon
JH,
I’d suggest those robot arms would add a fair bit. Plus the extra attachment points and associated reinforcing on the second-stage for the reattachment of the fairing and to support the arms.
I’d expect something on a par with the payload adaptor fitting, but with much more demanding design in order to berth and attach securely to, say, the thrust frame of the second-stage engine. (Because it’s vastly easier (& lighter) to design something only needs to release once in flight, versus something that needs to not only release, but also latch onto a moving target and lock it down securely for reentry and landing.)
And, of course, wrapping the upper-stage prevents you from being able to reuse the main US-engine during reentry. You can’t even use the attitude thrusters on second-stage, which means you need an entire extra set of thrusters on the fairing. And it means that your landing system needs to be built into the fairing, rather than just being attached to the existing thrust frame.
—
Aside:
Less elaborate than robot-arms: If the fairing is longer than the second stage, you might be able to have a simpler rotating pivot at the hinging point.
During satellite deployment, the fairings are hinged back 90 degrees (standard clamshell), so the concave inside points forward/upwards, then the fairing are rotated 180 degrees on their long axis so the inside faces to the rear, then they are hinged closed again. They never actually separate from the upper-stage skirt. The closures will still be more elaborate than the existing jettisoning system, because they have to realign the two halves. But I would expect the hinge+rotator mechanism to be simpler than even a single joint on a fully-fledged robotic arm.
Even if the fairings weren’t long enough, and had to be not only flipped, but moved down along the stage, a dumb pivot-arm added to the rotator mechanism is still much easier than a robot.
(It would be so much easier to draw those two images than try to find an existing image based on google-image results. I mean, a c-bracket pivot on a rotating mount, why is that so hard to find? I did find this though.)
I wonder if upper stages can be made recoverable with additional material launched separately. For example: transpiration coolant loaded into the empty stage in orbit to enable it to survive entry. Or, an entry shell wrapped around the stage at a recovery facility.
This doesn’t get rid of the mass penalty, but moves it to the side, so to speak, so it doesn’t affect the max payload of an individual launch so much. It would affect what orbits the launches can go to.
I’d think it would be simpler to just build a heat shield under/into the payload adapter. You’d have to figure out how to flip engine forward after entry, but wouldn’t need any complex moving parts. SpaceX apparently recovered the fairing after the last flight, so potentially the only thing disposed of would be the adapter parts in front of the shield.
Finally, a Selenian Boondocks post!
I’ve been thinking about upper stage recovery since SpaceX announced their intentions, and I’ve arrived at the following conclusions:
-Holding onto the fairings for the entire flight is quite expensive in terms of deltaV. They’re a non-negligible 1900kg. Keeping them is basically removing about 2 tons from the payload capacity. Adding heat-shielding elements makes this worse.
-Moving the shells around, as your design suggests, sounds very complicated to accomplish reliably. It makes extracting the payload tougher, and involves creating joints that move and lock across extreme environments.
-Not moving the fairings is equally troublesome, as it would perform reentry with most of the mass of an empty upper stage concentrated in the rear.
-Therefore, the most appropriate method for recovering the upper stage is to ignore the fairings and add a protective element at the base of the upper stage. It would be a heatshield that extends beyond the rim of the nozzle. For re-entry, doors close up the hole made for the nozzle. A pair of doors that swing open and shut is much easier to do than robotic arms that move the entire fairing and hold it in place.
-The bottom-heatshield concept can be improved with a nozzle that can collapse to allow for a shorter heatshield.
It might be easier, or at least much less mass, to run a coolant through the engine and out the nozzle.
Blunt heat shields work better.
https://en.wikipedia.org/wiki/Atmospheric_entry#Blunt_body_entry_vehicles