Stage Separation Technology

tahanson43206 · 2023-05-18 11:19:52

This topic is intended to focus on rocket stage separation.

I am asking our members to try (as much as possible) to stay on topic. I have invited Dr. Greg Stanley to join the forum to help with this topic.

The techniques used for stage separation of ** any ** vehicle are welcome, but this topic is created to support discussion of the new (untested) inertial stage separation technique reported to be in development for Starship.

2023/06/26 - Update: With the announcement of possible use of "Hot Stage Separation" I've revised the title of this topic to include all methods.

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tahanson43206 · 2023-05-18 11:21:28

For all ... here is a YouTube presentation by Dr. Greg Stanley about the rotating stage separation method for Starship.

https://www.youtube.com/watch?v=yesni8HUEA4

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SpaceNut · 2023-05-18 21:34:57

Tumbling end over end in the air was what caused the section between them to buckle bending and making it so that it could not pull apart.
There is the force of air drag on opposite sides of the ship that is spinning not at the center of length of the ship but is around the center of mass. Next as the ship comes through a single spin the starships engines must fire and if there is a buildup period for the engines to come on before throttle can set full then its going to enter a second tumble before it can pull apart.

tahanson43206 · 2023-05-19 06:15:11

For SpaceNut re #3

Thank you for helping to get this new topic under way!

The topic itself is intended to cover the development of an innovative state separation technique.

However, your post is a helpful reminder of the unplanned events we saw following the first experimental launch.

Hopefully at the next flight we'll get to see the new stage separation technique in "proper" operation.

The key "event" that ** must ** occur (as I understand Dr. Stanley's presentation) is that MECO must occur normally, with the caveat that a slight sideways motion must be imparted to the stack from the main engines just before MECO.

You didn't say anything about the video presentation in post #3

Is there anything you would like to see added to the video to help explain the planned technique? Greg Stanley asked for feedback;

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SpaceNut · 2023-05-19 18:31:33

Well let's look at the moments after a stage breaks apart of the other as they both spin in the same direction reacting over time to the difference in mass. A shift of the center of gravity begins to take place where the starships move from being near the engines to more towards the top of the tanks. This shift occurs as it makes the next complete revolution in time. All of which you are timing when to ignite the engines and throttle them up to continue the flight towards orbit. So, the amount of time to get fuel flowing and causing the engines to fire is very critical. As to late means wasting energy to change the shift upward trajectory.

Now lets focus on the booster at separation as it as well is shifting much in the same manner but the forward momentum is hoped to reduce such that the spin will not allow for a floating end over end but rather a settling of the center to the center of the length of the booster. Since there is fuel still onboard and pressure change in the tanks will cause a shift in mass while in its tumble all while the engines are still firing the rocket upward until 90' through the rotation to which the spin should slow an allow for a greater distance of separation to happen.

At some point during the remaining slow rotating of the stage it should start to fall and then we need to stabilize the end over end tumble by gimballing and throttling up the engines so that it can fall back to earth on the correct path. Shutting down the engines so that we save fuel until we need it.

tahanson43206 · 2023-05-19 19:51:17

For SpaceNut re #5

Thanks for continuing your development of the inertial stage separation idea!

One detail that might be worth further study/inspection/consideration is the angle needed to permit safe ignition of the Starship engines.

In your post, your wording suggests you are thinking of "one complete revolution". In contrast, I am imagining that 10 degrees of revolution of Starship is about right.

Here is an example of why having a computer animation would be so helpful!

In the early days of cartoon movie creation, artists were given the task of creating complete drawings of a scene every 30th of a second. Those images were then imaged, and the resulting series of images became a "moving picture", thanks to the lagtime built into our brains. In the absence of computer software to perform that service, human beings could still create animation using the ancient cartoon technique. If you (or someone) were to tackle the challenge of making drawings at the rate of one image per second, it should be possible to show the upper and lower stages rotating in opposite directions. At some point, it will be clear that the upper stage can ignite it's engines since exhaust will miss the booster. As soon as the Starship engines are running, the ship will pull away from the booster, which will then be free to perform it's own maneuvers.

It is in considering the motion of the booster that I can see your "full revolution" idea becoming a real possibility, with the caveat that the booster needs to revolve to just the right orientation so that it can begin it's reverse burn to return to the launch point.

I am guessing the rotation would need to be on the order of 270 degrees. It would NOT (I think) be a full 360 degrees, because that would put the booster back where it was shoving the Starship toward MECO.

In any case, thanks again for adding substantially to development of this topic.

I'd like to see some real numbers on the board. Words are fine to get the process started. Now it's time for some Real Universe numbers.

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SpaceNut · 2023-05-20 09:01:34

Only way to know for sure what angle and when to burn is from the data that was hopefully gathered from the less than perfect test theory of the past launch.

The big issue is that both parts are traveling still on the same angle of atmospheric attack when spin occurs. That means that the first 180' of rotation now has the booster tail in the nose orientation of the starship. Whether the booster has settled to its centers or is still shifting along its length is an issue for the units not hitting the starship.

All that is needed is a heat shield on the top of the booster's tank and no spin is required as you can just unlatch it and fire the engines of the starship to pull away from the booster.

update:
Heatshield material would be pica which is lite weight. Its only got to be thick enough for the startup of the engines and separation burn which is less than a dozen seconds. Since these are normally built to last minutes it's going to mot need as much thickness but in this case lets be safe in the design.

The rotation is making use of momentum and torque equations both contain mass and speed.

Also, the spin is creating AG and that centripetal force which is going to want to move liquids toward the ends of each rotating piece.

tahanson43206 · 2023-05-20 09:44:42

For SpaceNut re #7

Thanks for adding some creative ideas to the topic!

The idea of a heat shield on top of the booster is new (as far as I know).

It would add mass to the stage. Since this is your idea, please do some research to find out what material would be suitable for this application and how much it would weigh. In addition, please see if you can find out what kind of maintenance it would require.

This topic is about stage separation, and your idea most certainly fits squarely in the center of the range of possibilities. The Russians are said to have performed a simple burn of the second stage to remove the booster, but that method is appropriate if you are not trying to save the first stage.

Regarding the rotation .... you seem to still be working with words. Words are fine up to a point, but we need to go beyond words to actual calculations with accompanying illustrations. You don't have to do the work, if you can find an existing site that lends itself to the kind of calculations we need done.

Alternatively, you might enlist an existing member who can use Blender or Unreal Engine or another animation program to show by simulation how the Starship and the booster would separate and rotate under the SpaceX Inertial Separation plan.

If you have time and the energy, you can draw images of the upper and lower stages as they rotate after separation. This work could be captured on your smartphone and saved in imgur.com for display here.

I think you will find that about ten degrees of rotation is all that Starship needs to clear the booster.

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tahanson43206 · 2023-05-20 18:28:57

Here is an update of Dr. Greg Stanley's presentation on the recent SpaceX Starship test.

Apache did not like the original post ...

Starship test with the Super Heavy Booster, April, 2023: Description, problems, fixes coming
The original presentation included a discussion on Starship's innovative stage separation technique requiring no hardware beyond interstage clamps. This was split off into a separate video, with references given. There was some confusion during the test, when people thought the tumbling rocket was starting the new stage separation maneuver. But that tumbling was due to loss of control, not a failure of the new maneuver, which wasn't attempted because it required booster engine shutoff (which didn't happen).
This presentation is at
https://lnkd.in/gH7TmGuc (YouTube video, 18 minutes)
This and previous presentations are also available at
https://lnkd.in/evu8TJq
You can view or subscribe for notifications about new videos for free on YouTube channel gstanley0 at https://lnkd.in/gpp_brkt .
This was presented at the North Houston chapter of the National Space Society (NSS). The full meetings also include interesting guest speakers and discussion. You can attend in person, or online via Zoom. Come join us! The agenda for upcoming meetings, and presentations from this and past meetings are available at
https://lnkd.in/eefXxat

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SpaceNut · 2023-05-20 18:33:51

That means did we see the interstage clamps not open as required and that is why it failed?
Or did the rotation end up starting at an unplanned period in the launch path and not when it should have happened?

tahanson43206 · 2023-05-20 18:37:55

For SpaceNut re #10

Dr. Stanley attempted to explain the failure mode. The clamps never opened because the booster engines never shut down. The new Inertial Stage Separation technique requires the booster engines to shut down after performing the sideways jiggle. I think your closing sentence captures what happened nicely.

I decided to post the update because there might be additional links folks would be interested in investigating, beyond the report of the test launch.

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SpaceNut · 2023-06-10 07:25:16

tahanson43206 wrote:

This update is on feedback on the presentation about a possible inertial separation of Starship stages, first given at the May meeting of the North Houston chapter of the National Space Society. Video's about the presentation are available on YouTube.
Dr Greg Stanley wrote:
Sorry for the delay. I'm busy now researching Saturday's talk. I'll eventually get to your request to post something about the signup process for your site, although I may have already forgotten the details.
On your site, I looked the discussions involving the comments you passed back & forth between Gary and me, but couldn't find much. I guess a word for the site is "sprawling" and I haven't spent enough time on it to really figure out how to find things of interest yet.
One thing that may interest you is that the kind of comments Gary made also showed up in the comments in that YouTube video "Starship's innovative stage separation ... " at
https://youtu.be/yesni8HUEA4
. I was surprised at how much interest that video got. It's normally unusual if I get more than a few hundred views, maybe a few comments, and a few "likes". But so far that one registered over 69,000 views, 2,221 "likes" and 237 comments !
There were a lot of comments about how stage separation for an abort with a crew would work, how violent or long lasting the rotation will be, ullage (need for thrusters to ensure that the stage 2 engines will get liquid to start after separation), the destruction of the concrete pad, my mistake in saying the booster would do a "belly flop", my mistaken comment that the angular velocities of the individual stages would differ from the original velocity of the combined ship, my mistake in noticing that the Falcon 9 uses detonation cord for their "extended fairing", but somehow skipping over that they use the helium-powered pistons to push the standard fairing apart, etc.
To answer questions about the feasibility of that stage separation method, I started a spreadsheet to work through the centers of mass, moments of inertia, kinetic energy, angular velocity and linear velocity. The distribution of mass still needs work before really using it, but it's enough of a start that I think the method will be workable without involving any vomiting by astronauts. There's details in the comments, but here's a summary, pulled from several comments, of my start on the calculations:
-------------------------
re: Angular velocity of stages matches that of ship
Yes, the angular velocity of the separated stages matches the initial angular velocity of the ship, as I realized when I finally worked through the calculations. No matter what sort of variations apply (stage lengths, stage weights, distribution of weight within a stage due to payload or propellant), the end result is always the same angular velocity for the separate stages, matching the initial angular velocity. I'll have to look into how easy it is to modify videos already out on YouTube to fix this.
FYI, I worked through the calculations with a finite element approach, dividing the ship into 200 segments to place the mass based on dividing up the empty stage masses, the propellant masses, and the payload according to locations in the ship diagrams. Once that's in place, the spreadsheet calculates (before and after separation) centers of mass, moments of inertia, rotational and translational energy, linear velocities of the centers of mass, and verifies angular velocity for the separated stages given an initial angular velocity for the ship as a whole.
Based on dimensions and weights from Wikipedia, and eyeballing the rough locations of propellant tanks, etc., it looks like the center of mass (CM) of the ship prior to clamp release is around 255 ft from the bottom, which places it 25 feet up into stage 2. Stage 1 CM is at 101 ft. and stage 2 CM is at about 281, all out of a total height of 394 feet. Exact numbers depend on assumptions on stage 1 propellants remaining (I assumed 2% for my base case, and the CM for stage 1 is sensitive to that assumption), exact locations of the propellants in either stage which I only roughly approximated, and payload weight and distribution. This is just "ball park", and doesn't account for the heavier dry mass at the bottoms of stages due to the engines, or the differences in mass between LOX and methane (yet). This will be improved later.
People have been speculating on how violent and lengthy the rotation needs to be. From the test timeline at
https://www.space.com/spacex-starship-f … -explainer ,
there's only 5 seconds between clamp release on 2nd stage engine start.
If I assume an initial 0.1 radian/sec rotation (about 5.7 degrees/sec) about the ship center of mass, someone sitting at 80% of the height of stage 2 would experience that as about 10 - 11 ft/sec (right angles to the longitudinal axis). If the ship takes, say, 2 seconds to get to the desired angular velocity before MECO, that would imply a (lateral) acceleration of about 5 ft./sec^2, way less than normal gravity. The centers of mass of the stages after separation would move apart at about 18 ft./sec. So in 5 seconds, the stages center of masses drift apart by about 5*18 = 90 feet. In those same 5 seconds, their stage would have rotated 5*5.7 degrees = 28.5 degrees. And, as pointed out elsewhere, the stage 2 exhaust would be rotated, not pointing directly at stage 1. Are these acceptable sorts of numbers to not be considered "violent", and safe to avoid damage to the booster? Another commenter, @hendrik1745 , has suggested doubling that initial velocity, but has concerns about how the geometry really works out. This all needs to be refined, but suggests that the method won't be that stressful for an astronaut compared to all the other stresses from normal acceleration, going supersonic, decelerating before maxQ, maxQ, re-accelerating after maxQ, and then main engine cutoff going from high acceleration to weightlessness for the first time. We will probably just have to wait to see what happens when the method is tried, hopefully the next test.
Elsewhere, I did some look at the lateral acceleration an astronaut would experience from the rotation. It was pretty mild, way less than a G, and not lasting very long.
Another guy suggested 0.2 radians/sec might be a better choice, but I think we're in the ball park.
---------------------------
And another exchange,
-----------------------------------------------------------
re: ullage, subcooled liquid and autogenous pressurization helping, etc. :
@tedarcher9120 • 2 weeks ago
How would you light up the engines after that maneuver though? There is going to be a lot of bubbles in the tanks everywhere, you need starter motors anyway, why not just use them to separate?
gstanley0
• 2 weeks ago
This is just speculation, but I could think of a few possible reasons.
(1) Because Starship uses autogenous pressurization in the tanks (same pressurizing gas as the propellant) rather than a gas like helium, and significantly subcools both propellants (CH4 and LOX), it's likely that bubbles are less of a problem in the first place. Bubbles somehow forming in the liquid would just collapse and get absorbed into the liquid. That's unlike the case with, say, the Falcon 9 kerosene and helium, or LOX and helium. Although full autogenous pressurization won't have started yet in stage 2 (because of no heat from Stage 2 engines for vaporization), again, because there is so much subcooling in the loaded propellants, there probably hasn't been much time for much vapor to form. (And, really pure speculation) There might be some electrical heaters available for pressurization prior to engine firing, and maybe they even increase the pressure just prior to firing the engines to suppress bubble formation?
(2) The second stage is full just prior to separation and lighting up, so there is little vapor in the first place. The only vapor that would form would be because of heat passing into the tank from outside and vaporizing propellant. I realize that's not a completely convincing argument because you could say any second stage will initially be full, but with the subcooled liquid, until main (booster) engine cutoff, all the vapor would be up high, with little time to move down, and bubbles won't form spontaneously in subcooled liquid.
(3) The rotation must help, just like in a lab centrifuge used to separate things by density. Any gas bubble is lighter, and would tend to get displaced by the heavier liquid flowing to the bottom(outside), analogous to the case on earth where steady gravity keeps the liquid on the bottom. Unlike the case with linear acceleration, where things immediately start floating around as soon as the external force ( propulsion) stops, with rotation, the heavy liquid stuff would always flow towards the bottom.
(4) Lighting up stage 2 might be fairly quick, before there's much time for bubbles to make their way down to the bottom of the tank
(5) Starship has those small "header tanks", which are better insulated than the main tanks. They are always kept completely full of liquid, to ensure that even after a long time (unlike the case of initial launch), engines can be restarted using them before switching over to main tanks. They are there to handle landings without worrying about vapor, because by then subcooling would be lost and also the tanks are no longer full. They're only billed as being used for landings, but perhaps they could be used in the initial firing as well? My guess is they don't need to do that because of the other reasons above.

@tedarcher9120 • 2 weeks ago
@gstanley0 that's exactly my point. As starship rotates, heavy liquid will be pushed forward to the nose, and vapour at the top will flow towards the engines, snuffing them out. You'd need to stop the rotation and settle the liquid before lighting engines

@gstanley0
• 2 weeks ago (edited)
After separation, rotation of stage 2 will be around the center of mass of stage 2. Heavier stuff (liquid) will flow outwards from there. I don't know exactly where the center of mass is, and it would depend on how heavy the payload is. But, looking at a Starship diagram, e.g., at
https://everydayastronaut.com/definitiv … -starship/
it looks like the main LOX tank, the lower of the propellant tanks, is most likely all below the center of mass.
(I'm using "top" and "bottom" to refer to the configuration when standing vertically at launch time, with the engines at the bottom).
So, with liquids flowing outwards from the center of mass, that means most or all liquid oxygen will go to the bottom, keeping the engines fed with liquid. It's not as clear in the case of the methane tank. The main methane tank center looks to be somewhat below the geometric center of the rocket. As long as some portion of the methane tank is in fact below the stage 2 center of mass, then liquid methane flowing outward will keep the bottom of methane tank liquid. If that center of mass is indeed somewhere in the methane tank, then some liquid will also flow to the top of the tank. That would mean that any methane vapor would move towards that center of mass, which would be between the top and bottom of the methane tank. Eventually the vapor would all go there, but the stage 2 engine would start long before could happen... (see next comment)...
@gstanley0
• 2 weeks ago (edited)
(continuing...) I found a some details of the originally-planned timeline at https://www.space.com/spacex-starship-f … -explainer
Booster Engine cutoff is at 169 seconds into the flight, separation is at 172 seconds, and upper stage engine start is at 177 seconds. Up until engine cutoff, the liquid in both propellant tanks would be solidly at the bottom because of the linear acceleration. Then, there would be 3 seconds between booster cutoff and separation, when the rotation is about the center of mass of the combined ship, and the methane vapor could go down, as you were describing. It's not as clear for the LOX, because the center of mass of the entire combined ship might be in the LOX tank, or maybe not. But then there are 5 more seconds when the rotation just around the second stage center of mass would be helping to get propellant liquids back closer to the bottom. Given that there would be very little vapor in the first place (and starting with none in the wrong place), the SpaceX engineers must have worked all this out, and concluded it was unlikely that vapor would make it into the lines to the engines.
@hamjudo • 10 days ago
@gstanley0 some more supporting points. The methane downcomers are large pipes and thus represent a significant volume. The volume in the pipes below the center of mass is more than sufficient to start 3 engines.
SpaceX has tested a number of engines to destruction. They must know how well the engines recover from "small" gas bubbles. Where the upper end of "small" is defined as the largest bubble that is reliably recoverable.
The start up sequence itself involves running high pressure gas through the turbo pumps to get them up to speed. This gas is expelled out of the bottom of the rocket and will act just like a cold gas thruster.
-----------------------------------------------
And another exchange on human-crewed aborts with the new separation :
Several people have commented on this. For now, the focus is on getting the rocket ready for cargo only, following the usual SpaceX approach of doing that first, just like they did for the Falcon series. There's plenty to do for that as the top priority. That's a faster way to get to a minimum sellable product.
For the longer term, I'm sure they thought about that. It doesn't seem that unsolvable. For instance, as one other commenter pointed out, in an emergency, simply start the stage 2 engines and blast away - saving the booster isn't crucial in that case.
It's probably better than that. If the booster has burned out, then ullage (ensuring that only liquid propellant reaches the engine after some free fall) and some push-off from the booster can be provided by the cold gas thrusters at the bottom, fed from the propellant vapors (available because of the autogenous pressurization) and also because of the startup of the turbopumps at engine start. If the booster is still firing, then you already have the acceleration needed to keep the propellants liquid and still can blast away.
Emergency escape does depend on the unclamping working. But that approach has already been accepted as safe in the Falcon 9 series (and probably other rockets -- there's probably something like clamps to hold stages together). In the Falcon 9 case, they use pneumatic pistons to release the clamps. I don't know what they're using on Starship, but if it's pneumatic, the principles are the same. The difference might just be that there's no pressurized helium available like they use on Falcon 9. If they're still using pneumatics, maybe they use oxygen or methane gas, the only gases available -- I don't know. That's something to explore.
-------------------------------------
- regards,
Greg
________________
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SpaceNut · 2023-06-10 07:26:14

I think that the interstage folded due to mass and force of launch that caused the maneuver not to happen.

tahanson43206 · 2023-06-10 07:56:52

For SpaceNut re #13

Thanks for helping to give this topic a boost in it's early stages!

In thinking about your observation, it occurred to me that it is possible to build a simple model of the proposed stage separation technique out of 2x4's and a couple nails, and a bit of masking tape.

Let us imagine two 4 foot 2x4's held together at the ends by masking tape. To simulate the force of inertia put small rubber bands at the tips of each section. Adjust the tension of the rubber bands so that the 2x4's remain attached at the masking tape joint, but just barely. Let each 2x4 pivot about a nail midway along the 4 foot section.

Now, if all goes well, a whack on the bottom of the two 2x4's will cause the masking tape to give way, and the rubber bands will cause the 4 foot sections to rotate around the nail in the direction indicated by the placement of the rubber bands.

This simple visual aid could be offered to the local high school physics department, in hopes someone there is interested in trying to explain the Intertial Stage Separation technique.

For Void ... if you are inspired (and if you even see this post) please consider making one of your impressive drawings to show the proposed visual aid.

Update a bit later:

To make the model closer to the Real Universe rocket stack, it would make sense to put the pivot nail at the point where the center of mass is for each of the two sections. The strength of the rubber band can be adjusted to match (as closely as possible) the inertial forces at work.

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tahanson43206 · 2023-06-26 06:57:56

With the arrival of a post by Mars_B4_Moon, about "Hot State Separation" I've revised the title of this topic.

http://newmars.com/forums/viewtopic.php … 85#p211285

Members are invited to add posts with history of stage separation techniques used in the past, as well as ones that might be considered for the future.

GW Johnson has written a number of times about this specific topic, so links to that work would be welcome.

The difference between the SpaceX proposal Ias I understand it) and the Soviet version, is that SpaceX will attempt to protect the booster stage from harm, while igniting the second stage before actual separation.

It appears that vents are planned for escape of exhaust gases from the top of the booster while in flight, as well as a protective cap over the top of the propellant tanks in the booster. That will be ** some ** protective cap!

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Calliban · 2023-06-27 06:12:02

One option that I will throw into the mix here. If we use some sort of launch assist, that boosts rocket takeoff velocity to a minimum of 500m/s, we can dispense with the need for a two stage rocket and go SSTO. The space shuttle used about 1/3 of its fuel mass accelerating to 1000mph. Launch assist could save sufficient fuel to allow an SSTO to be possible. For small rockets, a modified gun (look up Project Harp) could serve this function. For larger rockets, a steam or natural gas powered cannon or rocket sled can provide the required velocity boost. The spin launch technology may offer some value here.

The challenge for a man rated rocket is acceleration. High acceleration also imposes high loads on the structure of the vehicle during the boost phase. So launch assist may increase structural margins, eating into the payload budget. Nothing comes for free.

Last edited by Calliban (2023-06-27 06:17:56)

tahanson43206 · 2023-06-27 09:58:16

For Calliban re #16

Thanks for addition of an alternate first stage technology.

Humans have most certainly been accelerating mass from a standing start to some velocity over thousands of years.

The technology has progressed to the point that now masses in the 10's of tons are routinely accelerated to flight speed for military purposes.

Your vision is for a system that accelerates hundreds of tons to 500 meters per second headed straight up.

Since this is the "Stage Separation Technology" topic, I would like to invite your addition of stage separation procedures for your alternate first stage concept.

SpaceX is (apparently) considering firing the second stage engines to push the first stage away. That might be a suitable concept for use with your concept.

It would require your giving some thought to how you would design the nose structure of whatever the first stage hardware might be.

I'd like you to continue developing your concept in a topic I'll create for that purpose.

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tahanson43206 · 2023-06-29 18:56:15

The quote below is from Greg Stanley's LinkedIn account.

It appears to be a quote from a SpaceX engineer about the change for the upcoming Starship launch attempt.

Sanjeev Sharma
Sanjeev SharmaSanjeev Sharma
• 2nd• 2nd
Principal Engineer, SpaceX Principal Engineer, SpaceX
4d • 4d •
Follow
Major change in stage separation for the upcoming Starship demo flight 2. Hot-Staging is when the second stage is ignited to push away from the first after main engines are cut off on the first stage. Although not new, it has never been done before on a reusable booster and saving the first stage from damage adds to the challenge in this case. It should be exciting!
#Starship #Spacex #rockets #spacetechnology

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tahanson43206 · 2023-07-01 16:53:09

As a reminder for NewMars members who are willing to run Zoom to attend meetings online, the NSS chapter in Houston (North to be specific), will be opening the session for July on the Second Saturday at 2 PM Houston time 3 PM EST. Dr. Greg Stanley will be offering his report on space activity for the month, and I would be astonished if he did not allocate a few minutes to the new Hot Stage Separation concept that is in the news recently.

NewMars members who attend the event are NOT expected to turn on Video or Audio, and I notice that most attendees in recent times have these features turned off. There is a chat service that is (somewhat) attended. I'll ask my contact at the chapter to see if there is a volunteer willing to monitor the chat more closely.

There are chances that the quality of the video feed will improve over time. A professional has (apparently) volunteered to handle video, although whether that extends to the online experience is not clear to me at this point.

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GW Johnson · 2023-07-03 07:53:10

This is an old Russian staging technique developed long ago in the expendable liquid launcher/ICBM days. The lower stage had to be just tough enough not to burst or explode during the upper stage push-away event. They typically used an open truss as the interstage to vent the plumes ricocheting off the front of the lower stage.

SpaceX is going to have to accept the greater inert weight of enough hot blast shielding on the front of the lower stage to prevent damage, in order to re-use it. That increase in inert mass comes right out of net stage payload capacity. It also increases the return-and-land propellant quantity, which also comes directly out of stage payload capacity.

Life is complicated in the reusable rocket business.

GW

Last edited by GW Johnson (2023-07-03 07:54:03)

tahanson43206 · 2023-07-03 10:03:01

For GW Johnson re #20

Thanks for contributing to the topic in the days before Dr. Stanley offers his analysis at the upcoming Houston meeting.

it occurs to me there might be a place for ablative material in this situation. You've pointed out the extra mass needed for the nose shield. On the other hand, using this technique (apparently) means a savings of energy for the second stage, which has a shorter wait time before ignition after first stage cut off.

If the nose protection is ablative, then that mass will be dispersed and will not be a concern for landing.

On the ** other ** hand, this means the cone material has to be replaced for each flight.

I would imagine Greg Stanley is diving deep into his resources to try to be ready for Saturday.

(th)

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#13 2023-06-10 07:26:14

Re: Stage Separation Technology

#14 2023-06-10 07:56:52

Re: Stage Separation Technology

#15 2023-06-26 06:57:56

Re: Stage Separation Technology

#16 2023-06-27 06:12:02

Re: Stage Separation Technology

#17 2023-06-27 09:58:16

Re: Stage Separation Technology

#18 2023-06-29 18:56:15

Re: Stage Separation Technology

#19 2023-07-01 16:53:09

Re: Stage Separation Technology

#20 2023-07-03 07:53:10

Re: Stage Separation Technology

#21 2023-07-03 10:03:01

Re: Stage Separation Technology

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