Do y'all think the Space-X Super heavy/Star ship would work out?

[NSEP]

On 1/26/2019 at 5:35 AM, Ultimate Steve said:

Sorry to interrupt the argument, but if the whole extremely rapid reuse thing works out, at what point do you think will they stop livestreaming some launches because it won't be worth it any more?

Maybe, but they could also have a 24/7 stream of the spaceport up, with a countdown to whatever launch is coming up next. Would look very cool.

Speaking of LES... They could also have some sort of 'glider' attached to Starship as an LES.

Just a crazy little thought though.

Edited February 4, 2019 by NSEP

[sh1pman]

TBH, the more I think about it, the more I become convinced that LES on a Starship is a bad idea.

[kerbiloid]

The Starship emergency kit,
 

Spoiler

Tier 0. (Passive)

Spoiler

Tier 1. (Active).

Spoiler

 

 

[DDE]

1 hour ago, sh1pman said:

TBH, the more I think about it, the more I become convinced that LES on a Starship is a bad idea.

A lot depends on what the payload section of the stack is.

Which is still an unknown. For a cislunar expeditionary vehicle, an escape pod appears plausible.

Edited February 4, 2019 by DDE

[tater]

There's so much excess capacity on this vehicle for a small crew (where small is redefined upwards compared to every other rocket in history, lol) that it seems like a LES pod is entirely feasible. Such an addition would make the vehicle vastly more attractive during early use as a crew vehicle.

[sh1pman]

1 hour ago, tater said:

There's so much excess capacity on this vehicle for a small crew (where small is redefined upwards compared to every other rocket in history, lol) that it seems like a LES pod is entirely feasible. Such an addition would make the vehicle vastly more attractive during early use as a crew vehicle.

The reason why I don't think LES is a good idea is because it only covers a tiny fraction of possible failure situations. It can only save lives if a failure happens during the burn of Super Heavy or shortly after the stage sep. LES is useless later into the launch. It won't help if a failure happens in orbit, during tanker randezvous, docking, refilling, departure burn, in transit to Mars/Moon, during atmospheric entry and landing, on the surface of another body, during liftoff from that body, burn to Earth and Earth atmospheric entry. It needs to be safe in all of these situations, not just first few minutes of launch. Airplanes are as safe as they are now not because passengers have escape pods.

So I think that instead of investing their time and money into the implementation of Starship LES, SpaceX should focus on making failures less likely.

Edited February 4, 2019 by sh1pman

[StrandedonEarth]

But it would have the capacity for a full-on escape pod, complete with heat shield and de-orbit capability. The biggest problem would be making it too top-heavy, especially if trying to pack enough propellants for a cis-lunar return. It all depends on the architecture of the system.  But it’s nigh impossible to plan for every contingency in a reasonable fashion. 

[tater]

Edited February 4, 2019 by tater

[DDE]

2 hours ago, sh1pman said:

The reason why I don't think LES is a good idea is because it only covers a tiny fraction of possible failure situations. It can only save lives if a failure happens during the burn of Super Heavy or shortly after the stage sep. LES is useless later into the launch. It won't help if a failure happens in orbit, during tanker randezvous, docking, refilling, departure burn, in transit to Mars/Moon, during atmospheric entry and landing, on the surface of another body, during liftoff from that body, burn to Earth and Earth atmospheric entry. It needs to be safe in all of these situations, not just first few minutes of launch. Airplanes are as safe as they are now not because passengers have escape pods.

So I think that instead of investing their time and money into the implementation of Starship LES, SpaceX should focus on making failures less likely.

The expected high launch tempo of the Starship increases chances for a recovery mission in all but a handful of situations. The LES needs to cover that handful of situations.

[Rakaydos]

2 minutes ago, DDE said:

The expected high launch tempo of the Starship increases chances for a recovery mission in all but a handful of situations. The LES needs to cover that handful of situations.

Pair of OTS Dragon2 capsules mounted in the Starship's main cargo hatches, to carry the 14 passangers of the DearMoon mission, or equivilant flights. Emergency Life support for the entire trip, reentry capability, orbital maneuvering ability, and the ability to horizontally abort in the event of a launch failure, using the Superdraco thrusters. (programmed to curve the trajectory upward if they deploy without the altitude for parachutes)

[DDE]

32 minutes ago, Rakaydos said:

Pair of OTS Dragon2 capsules mounted in the Starship's main cargo hatches, to carry the 14 passangers of the DearMoon mission, or equivilant flights. Emergency Life support for the entire trip, reentry capability, orbital maneuvering ability, and the ability to horizontally abort in the event of a launch failure, using the Superdraco thrusters. (programmed to curve the trajectory upward if they deploy without the altitude for parachutes) 

As previously proposed, and as I previously countered, they might not curve fast enough.

Finally... sadly, there's probably a requirement for a huge window.

[Rakaydos]

3 minutes ago, DDE said:

As previously proposed, and as I previously countered, they might not curve fast enough.

Finally... sadly, there's probably a requirement for a huge window.

So the best you can come up with is that it MIGHT not be enough?

[DDE]

Just now, Rakaydos said:

So the best you can come up with is that it MIGHT not be enough?

Yeah. The hoverslam leaves little room for classic LES abort. Wasting precious milliseconds to reorient the ejected capsules, preferably without tearing them apart, is not an option.

[Rakaydos]

1 minute ago, DDE said:

Yeah. The hoverslam leaves little room for classic LES abort. Wasting precious milliseconds to reorient the ejected capsules, preferably without tearing them apart, is not an option.

During hoverslam, the Starship is already subsonic. Abort thrusters can easily zero vertical velocity that and rotate for parachute deployment. it may not be gentle, but we're talking requirements for NASA here, not civilians willing to sign a waiver.

[tater]

Landing failures have 2 possibilities. Either it's like the last booster landing failures, in which case it ejects the crew at the best moment, since it's clear it's not making the LZ, or at the very end of the landing burn, when it's already over (or very close) to the LZ, and is moving pretty slowly. In both cases any LES would work just fine, they're easy cases compared to maxQ.

[Mad Rocket Scientist]

I think the idea is that once there are many flights of starship, a lack of LES won't be a problem, it's only in the short term, where starship resembles a experimental aircraft (which would have ejector seats) rather than a passenger airliner. Some kind of shuttle-esque ejector seats for the small number of crew on the first few crewed flights makes sense.

[Xd the great]

How would the turn to cold thruster for RCS affect the starship capabilities?

[Rakaydos]

25 minutes ago, Xd the great said:

How would the turn to cold thruster for RCS affect the starship capabilities?

less ability to land in rough earth weather, so point to point is out till the RCS is upgraded. Certantly no landing in launch clamps for Superheavy.

[IncongruousGoat]

20 minutes ago, Rakaydos said:

Certantly no landing in launch clamps for Superheavy.

Well, they seem to be moving away from that anyways. Makes development a lot easier if they just have to match the landing accuracy they've achieved for Falcon 9, rather than trying to push the envelope on pinpoint landing.

[Rakaydos]

8 minutes ago, IncongruousGoat said:

Well, they seem to be moving away from that anyways. Makes development a lot easier if they just have to match the landing accuracy they've achieved for Falcon 9, rather than trying to push the envelope on pinpoint landing.

Technically, they only needed to match falcon 9's absolute accuracy- the larger superheavy means the RELATIVE accuracy is much smaller.

Missing by a meter is 1/3 a falcon, but 1/9 a starship, after all.

[tater]

Musk already tweeted that Super Heavy gets fins, so landing on the clamps isn't a thing. Which is great.

[kerbiloid]

Aren't they using that maraging steel, like Sea Dragon and Convair Nexus were going to?

I've just read in wiki that Raptor is pump-fed, with ~30 MPa working pressure.
Why 40 pumps? Why not use that thick-wall pressure-fed old-school design?

_{(I thought, Raptor is pressure-fed.)}

***

Just noticed a picture. 
http://www.up-ship.com/eAPR/ev3n1.htm

Spoiler

Werner von Braun's Ferry Rocket
 

Von Braun's early 1950's concept for a three-stage fully reusable "Ferry Rocket" that anticipated the Saturn V in size and the Space Shuttle in role.

It looks strangely familiar.

Edited February 5, 2019 by kerbiloid

[Rakaydos]

38 minutes ago, kerbiloid said:

Aren't they using that maraging steel, like Sea Dragon and Convair Nexus were going to?

I've just read in wiki that Raptor is pump-fed, with ~30 MPa working pressure.
Why 40 pumps? Why not use that thick-wall pressure-fed old-school design?

_{(I thought, Raptor is pressure-fed.)}

Sea Dragon was designed to be built 100% in a naval shipyard in the 60s/70s by unskilled workers. That includes the massive engine, which meant that the engine really couldn't be that complex. A pressure fed bipropellant engine is about two steps up from a bottle rocket/cold gas thruster in complexity, and something the designer thought was manageable at shipyard tolerances, instead of rocket-science tolerances.

Mueller isn't building Raptor in a marsh in texas, though Elon may for the rest of the rocket. It's small enough to be put on a truck, so there's no problem building it elsewhere and installing it there. He can design it to be the best reusable rocket engine, not just in the world, but the best that an experienced early 21 century rocket engineer is capable of designing with effectively unlimited design funding.

"Merlin has the best TWR in the world, but Raptor is coming."

[DDE]

1 hour ago, kerbiloid said:

I've just read in wiki that Raptor is pump-fed, with ~30 MPa working pressure.
Why 40 pumps? Why not use that thick-wall pressure-fed old-school design?

_{(I thought, Raptor is pressure-fed.)}

 

The BFR is probably not at a point where the square-cube law avenges the notorious mass inefficiency of high-thrust pressure-fed rockets.

[Xd the great]

16 minutes ago, DDE said:

The BFR is probably not at a point where the square-cube law avenges the notorious mass inefficiency of high-thrust pressure-fed rockets.

Considering the fact that raptor engines are relatively small, no.