sojourner
-
Posts
923 -
Joined
-
Last visited
Content Type
Profiles
Forums
Developer Articles
KSP2 Release Notes
Bug Reports
Posts posted by sojourner
-
-
4 hours ago, CSE said:
Each step needs to be small enough that customers have confidence they're buying the same thing they, and their insurers, are familiar with
The customers don't care about the fate of the first stage once the second stage has separated.
-
I could see a development of the "roomba" used on the barges as a landing pad that "centers" itself on the incoming ITS booster. It would obviously have to be much bigger than the current roomba and you would have to be careful to avoid a feedback loop of the roomba trying to center and the booster also trying to center, but it makes sense to work it out for that last few feet of landing.
The key there would be to have the booster ignore the roomba and focus on a fixed landing point while the roomba is focused on lining up with the hardpoints on the booster to grab it.
-
49 minutes ago, sevenperforce said:
Very nice catch.
I was actually going to ask this question myself.
In a really, really ridiculously bad situation -- like, meteoroid impact that takes out the Soyuz lifeboat and the life support systems and gives the astronauts only a matter of hours -- would a docked Dragon 1 be enough to get the crew home safely? They'd need to bring their own air and such, obviously.
Dragon 1 berths, not docked. Someone would have to remain onboard the ISS to unberth it.
-
5 minutes ago, Mitchz95 said:
That wasn't a reused rocket, though, was it? Just the Dragon.
Maybe by "reuse" he really meant "land".
-
That's getting easier as SpaceX is ramping up to a launch every two weeks. It'll be even more frequent once they get both pads back in operation this fall.
-
19 hours ago, kerbiloid said:
bicycles are prohibited outside of recreation zones;
LOL.
Titan may not be economical to mine for use on Earth, but in some far flung future it will be the economic power house of the Saturn system.
-
2 minutes ago, Mad Rocket Scientist said:
SLC-4E is the VAFB launch site. I believe it is ready for FH as it already has the FH strongback. It might need to be modified for the "throwback," though.
I believe that's the old strongback and probably no longer works for FH. Regardless, SpaceX has already said that debut launch of FH will be from LC-39a and that updating the pad is the long pole now on when it will launch.
-
1 minute ago, TheEpicSquared said:
Do you mean SLC-40? SpaceX is using 39A already.
Doh, fixed.
-
5 hours ago, Mad Rocket Scientist said:
I think FH could launch from SLC-4E right now.
Nope, they have to do some final work to make LC-39a compatible with FH and they can't afford the downtime until they get SLC-40 back in operation.
-
14 hours ago, kerbiloid said:
Most likely the crew cabin would be ejected during the ascent phase. So, no possible transfer.
Which is not orbital velocity and would not need a heatshield. As demonstrated by Falcon first stage.
-
5 hours ago, kerbiloid said:
When its velocty is just hypersonic.
The rescue capsule must survive total reentry with orbital speed.
From my original post:
If the vehicle gets compromised for use on re-entry you're pretty much stuck where every other vehicle would be if it's heatshield has been compromised: having to do a crew transfer on orbit to another vehicle. Unless of course this monstrosity of a system has enough payload mass to allow for the crew pod to have it's own secondary heatshield. But that's really starting to cut into the mass of the vehicle for scenario that has only occurred once in the history of manned space flight.
-
11 hours ago, kerbiloid said:
At high altitude they also need a heatshield and aerodynamic shape, not just a nice cylinder.
Not true. Falcon 9 first stage does just fine without a heat shield. A heat shield is only really necessary if you need to shed orbital velocity.
pad abort would be the tricky part with a side ejecting pod. Low altitude shouldn't be a problem. Depending on what you mean by "low". The abort motor system would have to be designed to take the pod laterally at first to clear the rocket and then curve into a vertical climb to give it enough altitude to deploy chutes.
-
Build a secondstage/spacecraft with a bi-conic profile. give it cargo bay doors similar to shuttle. Send crew up as cargo in a pod in the bay. Launch abort sideways after blowing the doors. Or go a step further for crew mission and remove the doors and have the crew pod fit in flush (this would also allow for much easier access to a docking port for in space transfers_. Separate everything needed by the crew from the vehicle to the pod.
If the vehicle gets compromised for use on re-entry you're pretty much stuck where every other vehicle would be if it's heatshield has been compromised: having to do a crew transfer on orbit to another vehicle. Unless of course this monstrosity of a system has enough payload mass to allow for the crew pod to have it's own secondary heatshield. But that's really starting to cut into the mass of the vehicle for scenario that has only occurred once in the history of manned space flight.
-
The G's pulled by a launch abort system would trash pretty much any satellite you tried to save with it. Designing satellites tough enough to survive a launch abort would be prohibitive in mass usage. Most of the mass of the satellite would be taken up for a scenario that would be only seconds of it's planned life. It's cost prohibitive.
This is why payload customers are perfectly fine with holds and scrubs for the least little variable out of range. Better to wait a day and fix that out of range sensor than take a chance with a multi-million dollar payload.
-
22 hours ago, Terwin said:
As the second stage gets into LEO, why would it not complete most of an orbit and land back at it's launch point with just a reentry burn?
It seems that not needing a boost-back would greatly reduce the amount of fuel that needs to be reserved.
Presumably spending an extra hour or so in space should not be much of a hard-ship compared to reentry...
Who said it would do a boostback? The assumption has always been to go one orbit and land at a convenient location.
-
-
7 hours ago, sevenperforce said:
The consumables tanks could probably be much smaller, but getting fold-out landing legs requires a lot of space.
Don't use fold out legs. Use popout peg legs like on Crew Dragon.
EDIT: Hehe, this is sort of weird having this conversation across two forums. Though I am more of a lurker on NSF.
-
2 hours ago, sevenperforce said:
Following up on this, consider what has to go into a "full" recovery module adapter:
- Heat shield
- Payload attachment points on/around/under heat shield
- Thrusters
- Propellant tanks
- Pressurant tank(s)
- Landing legs
There's a chance you could pressurize the legs and the thruster prop tanks from the main-stage pressurant COPVs, but that would require re-plumbing of the main tank, and I'm not sure the Falcon COPVs have enough helium pressure to successfully run pressure-fed thrusters. The SuperDracos have a chamber pressure of 6.9 MPa.
Consider also that the thrusters and the landing legs both need to be outside of the re-entry plasma impingement region. For the thrusters, this probably means being set significantly back inside the module with associated cosine losses. The landing legs are also problematic, since space is really limited. Using the Dragon 2's pop-out landing struts is not ideal due to the much greater height of the second stage; even a slight puff of wind would tip it over. The recovery module is also going to increase the effective height of the stage, significantly.
Geometry is a limiting factor, here.
EDIT: For example, here's what the difference might look like...
First from left is the current Stage 2. Second from left would be the second stage with recovery adapter and flaps added. Third shows recovery adapter and feathered flaps on re-entry; fourth shows landing burn (high cosine losses) with legs extended. Obviously it would be balanced; this only shows one thruster and one landing leg for the sake of simplicity. The tanks shown are helium pressurant and hypergolic bipropellant.
I think your depiction of the recovery adapter is WAY too large.
-
That looks really heavy. Not sure you would have any worthwhile payload left.
-
Well, those are all good points on why it wouldn't work. Back to the drawing board....
Thanks for the informative posts!
-
Doh, my bad for posting after just waking up. Wasn't thinking straight.
-
2 hours ago, Frozen_Heart said:
Shush. You'll give elon ideas.
It's an old video. The trunk stays attached to the first stage now. It comes back with every returned first stage.
-
I have a quick question. Hypothetically how hard would it be to convert a standard rocket engine, say a Merlin Vacuum engine, to use an aerospike instead of the large nobium nozzle currently in use? If it could be done, would the resulting engine be use able from sea level to orbit? If so, this would seem to help make F9 second stage return much easier.
-
Why not put heat resistant grid fins at the base of the stage that would open up in a "shuttle cock" configuration? Could that achieve enough stability for re-entry? We already know that F9 Block 5 is getting titanium grid fins that are more heat tolerant. Maybe they are thinking of 2nd stage recovery as well with that change? Heck, with some smart engineering they could even integrate the landing leg system into the gird fin/shuttlecock system. If you're going to add weight make it work for you too..
SpaceX Discussion Thread
in Science & Spaceflight
Posted
Those are the new titanium grid fins.