Abort options for Starship and Starship/SuperHeavy

[Lee Jay]

I think some posters here (especially Lee Jay) have essentially fallen for: familiar = safe, unfamiliar = unsafe

No.

Intrinsically flies - safer than intrinsically falls.
Can land in a wide area - safer than must land at a specific spot.

SS falls, has to flip under power and then land at a very specific spot - unsafe.

Not if they decide to use legs for the crewed starships. Airliners have very questionable safety if they lose all engines. The likely result is loss of airframe and everyone on board, not any different from Starship.

22 of 41 listed here (https://en.wikipedia.org/wiki/List_of_airline_flights_that_required_gliding) have 0 fatalities.  Only one had all passengers die, and that was because of flight crew incapacitation.  2 more had the pilots die when they were the only ones on board (no passengers).  In 35 of those 41 the majority of the people on the plane survived.

How survivable do you think a SS landing without engines is?  How likely is that to occur compared to airliners?  That article found 41 instances since 1953, and some were due to crime.  There are currently around 100,000 flights per day of commercial airliners globally.

Using legs for crewed starships would probably help a little in those instances where they had a place to land and were off-course or if the wind weren't right for them to be caught.

[chopsticks]

Intrinsically flies - safer than intrinsically falls.

Just want to push back a little on this point. The 4 control surfaces on starship are just that - control surfaces. You will probably end up with people dead on dreamchaser for example (just to name a spaceplane) if you lose an elevon (or elevator, not sure what they call them). A plane intrinsically flies, as long as it's controllable. A vehicle like Starship falls, but also needs to be controllable. Not a lot of difference in this regard IMO.

[eriblo]

I think some posters here (especially Lee Jay) have essentially fallen for: familiar = safe, unfamiliar = unsafe

No.

Intrinsically flies - safer than intrinsically falls.
Can land in a wide area - safer than must land at a specific spot.

SS falls, has to flip under power and then land at a very specific spot - unsafe.

Not if they decide to use legs for the crewed starships. Airliners have very questionable safety if they lose all engines. The likely result is loss of airframe and everyone on board, not any different from Starship.

22 of 41 listed here (https://en.wikipedia.org/wiki/List_of_airline_flights_that_required_gliding) have 0 fatalities.  Only one had all passengers die, and that was because of flight crew incapacitation.  2 more had the pilots die when they were the only ones on board (no passengers).  In 35 of those 41 the majority of the people on the plane survived.

How survivable do you think a SS landing without engines is?  How likely is that to occur compared to airliners?  That article found 41 instances since 1953, and some were due to crime.  There are currently around 100,000 flights per day of commercial airliners globally.

Using legs for crewed starships would probably help a little in those instances where they had a place to land and were off-course or if the wind weren't right for them to be caught.

Just a note I find interesting as a (para)glider pilot - powered aircraft will by design not reach the runway if they lose all engines on final approach...

[Lee Jay]

I think some posters here (especially Lee Jay) have essentially fallen for: familiar = safe, unfamiliar = unsafe

No.

Intrinsically flies - safer than intrinsically falls.
Can land in a wide area - safer than must land at a specific spot.

SS falls, has to flip under power and then land at a very specific spot - unsafe.

Not if they decide to use legs for the crewed starships. Airliners have very questionable safety if they lose all engines. The likely result is loss of airframe and everyone on board, not any different from Starship.

22 of 41 listed here (https://en.wikipedia.org/wiki/List_of_airline_flights_that_required_gliding) have 0 fatalities.  Only one had all passengers die, and that was because of flight crew incapacitation.  2 more had the pilots die when they were the only ones on board (no passengers).  In 35 of those 41 the majority of the people on the plane survived.

How survivable do you think a SS landing without engines is?  How likely is that to occur compared to airliners?  That article found 41 instances since 1953, and some were due to crime.  There are currently around 100,000 flights per day of commercial airliners globally.

Using legs for crewed starships would probably help a little in those instances where they had a place to land and were off-course or if the wind weren't right for them to be caught.

Just a note I find interesting as a (para)glider pilot - powered aircraft will by design not reach the runway if they lose all engines on final approach...

Yeah, I sort of hate that.  I fly R/C and, in my life, probably 95% of my landings have been dead stick on purpose, just because I'd rather have the runway made and chop than require power all the way down the way that 3 degree glideslope does.  But it seems to work since modern engines are quite reliable and, if they do fail, it's unlikely to happen at this point in the flight profile.

When I have a real dead stick on R/C (which is pretty rare for me, but it has happened), it tends to be pretty uneventful because I've practiced that a few tens of thousands of times.

[Lee Jay]

Intrinsically flies - safer than intrinsically falls.

Just want to push back a little on this point. The 4 control surfaces on starship are just that - control surfaces. You will probably end up with people dead on dreamchaser for example (just to name a spaceplane) if you lose an elevon (or elevator, not sure what they call them). A plane intrinsically flies, as long as it's controllable. A vehicle like Starship falls, but also needs to be controllable. Not a lot of difference in this regard IMO.

There are redundant flight controls on DC.  Each one has redundancy and you can lose some of them and still have control.

[sebk]

I think some posters here (especially Lee Jay) have essentially fallen for: familiar = safe, unfamiliar = unsafe

No.

Intrinsically flies - safer than intrinsically falls.

First, vertically landing F9 first stage has already longer success chain than any space plane returning from space ever had. And the damn thing does so on an unredundant engine with unredundant hydraulics, and most frequently landing on a bobbing patch of metal in the middle of the sea. So long with "intrinsically flies".

Second, by that very logic cars are safer than planes. Intrinsically could stop any time - safer than intrinsically plunges if stopped. "Right?"

Third, you got fixated on the final subsonic part of  the entire flight. That's a fundamentally broken approach. Because vehicles able to pass through the hypersonic part (that one you complained about extreme temperatures and stuff) fly poorly subsonically while they are not passively stable hypersonically. If you make it passively stable hypersonically (passive stability is a requirement for transport planes for a reason) it becomes unusable subsonically (except for tiny vehicles) due to excessive landing speed and excessive descent angle.

Can land in a wide area - safer than must land at a specific spot.

So vertically landing vehicles beat space planes hands down. A vertically landing vehicle needs a small patch of reasonably flat land. Space plane needs long runway, space plane of capacity comparable to Starship requires exceedingly long runways, so long they don't exist. And landing off runway is not survivable for such a vehicle (sliding at 250km/h is maybe survivable for the majority of occupants, sliding at 400km/h is not).

SS falls, has to flip under power and then land at a very specific spot - unsafe.

Wrong. It could emergency land on any flat patch of land. Contrary to space planes which are runway or bust. But the whole reasoning is fallacious in the first place anyway.

[pathfinder_01]

Wrong. It could emergency land on any flat patch of land. Contrary to space planes which are runway or bust. But the whole reasoning is fallacious in the first place anyway.

Without legs that could be a problem as the current version of starship is using a catch system. I think the only possible abort option will be an abort to orbit followed by a controlled landing somewhere.  It is going to have to be more like a passenger jet were most of the options are survive long enough to land on a runway.  As it stands now the biggest flaw in terms of abort options isn't lacking an abort system per say but no real options if you can't get to the landing spot.  I have my doubts that landing a vehicle with hot engines and cold cryogenic propellant in the ocean is survivable.  I also don't think an abort system is practical for a vehicle like this.

[Lee Jay]

I think some posters here (especially Lee Jay) have essentially fallen for: familiar = safe, unfamiliar = unsafe

No.

Intrinsically flies - safer than intrinsically falls.

First, vertically landing F9 first stage has already longer success chain than any space plane returning from space ever had.

First of all, that isn't true (F9 - 80, Shuttle, 106).  Second of all, it has legs - big ones - and lands on improved surfaces.

Second, by that very logic cars are safer than planes. Intrinsically could stop any time - safer than intrinsically plunges if stopped. "Right?"

Apples and oranges.  Cars are safe until there are other cars around.  Planes have HUGE separation distances (thousands of feet to miles) compared to cars.

Third, you got fixated on the final subsonic part of  the entire flight.

And the launch.  EDL isn't a sure thing either.

So vertically landing vehicles beat space planes hands down.

No cross-range, and no-legs kill that idea entirely.

A vertically landing vehicle needs a small patch of reasonably flat land.

And legs that can handle the un-flatness of whatever you land on.  And "reasonably flat land" isn't as common as you think.

Space plane needs long runway,

But can fly to it because it has cross range, rather than being ballistic.

DC can land in 6 hours at most (1 hour much of the time), starting from any time.  Dragon can't, despite having 3/5ths of the planet that's theoretically suitable for landing.  Being able to steer is a big deal, and runways are all over the place.

[Barley]

I think some posters here (especially Lee Jay) have essentially fallen for: familiar = safe, unfamiliar = unsafe

I'd put it somewhat differently:  unknown = not provably safe.

nkn
Not provable != Not proven.


"Not provable" is an assertion that no proof can ever exist.  "Not proven" is an assertion that no proof is known.

[TheRadicalModerate]

I think some posters here (especially Lee Jay) have essentially fallen for: familiar = safe, unfamiliar = unsafe

I'd put it somewhat differently:  unknown = not provably safe.

nkn
Not provable != Not proven.


"Not provable" is an assertion that no proof can ever exist.  "Not proven" is an assertion that no proof is known.

“Not yet provable” is adequate for the argument.

[Barley]

So (I ask again), which is the better strategy:  Wait however long it takes to get the flight heritage, or build an escape system, even if it's just a stopgap? 

Be careful not to let the perfect be the enemy of the good.  You can always get rid of a launch escape system if you have the data to prove that it isn't useful.  But missed opportunities are forever.

I do not believe that an escape system will ever be a stop gap.  If you have one you will never get rid of it, even if it becomes provable harmful.

Dragon has an escape system because STS did not, and Apollo, Gemini and Mercury did.  Mercury had one because rockets were blowing up with regularity at the time.

Straightforward decisions, missed opportunities, and opportunity cost run the other way if you want to settle the solar system.  The cost of forcing an escape system may be infinite.

If you need a stop gap use Dragon on F9.   If SS works* eventually that will look ridiculous and may go away.

* If SS does not work well enough for human flight without an escape it does not matter, we will not be settling the solar system on it.

[Barley]

And "reasonably flat land" isn't as common as you think.

and runways are all over the place.

Reasonably flat land is at least as common as runways

Runways are reasonably flat, if you can land a spaceplane you can land vertically. 

[TheRadicalModerate]

I do not believe that an escape system will ever be a stop gap.  If you have one you will never get rid of it, even if it becomes provable harmful.

There's a good reason to get rid of it ASAP:  Until you do, Starship can launch crews of 10-12, not 50-100.

[re-ordered a bit for purposes of the argument]

If you need a stop gap use Dragon on F9.   If SS works* eventually that will look ridiculous and may go away.

* If SS does not work well enough for human flight without an escape it does not matter, we will not be settling the solar system on it.

If D2 will work as a stopgap, I think that's a better solution (as I've droned on and on about in the LSS threads).  But the economics are important.¹  I think there's decent demand for private lunar surface missions, which are a nice source of profit, a nice way to put pressure on NASA, and a nice way to get lots of refueling heritage.  But it's going to be sensitive to price/seat, and it'll be hard to hit the right point with a D2 that only launches a crew of four.

And there's a big difference in the interplanetary exploration risk profile vs. the risk profile for a surface-LEO ferry (or, for that matter, a surface-LMO ferry, once a decent base is up and running).  Also, time is on your side with interplanetary, because it's not happening at scale for quite a while.

Dragon has an escape system because STS did not, and Apollo, Gemini and Mercury did.  Mercury had one because rockets were blowing up with regularity at the time.

I'd think that CCP systems have escape because STS was deemed, in retrospect, to have an unacceptably high pLOC (~1/100), and escape for a traditional stack is a pretty cheap way of reducing pLOC.  There's no doubt that Starship is harder (that's what this thread was supposed to be about).  But you have to make trades between opportunity cost and waiting for the non-escape reliability to be adequate.



______________
¹Three things that might improve the economics of a D2-based system enough for it to be the only stopgap:

1) Going back to crews of 7 for the D2.  This is almost certainly the biggest bang for the buck--if it's possible.  My understanding is that the main reason for cutting back to 4 was parachute and landing risk with the seats oriented through the axis of symmetry.  Private crews will accept a little bit more risk--or pain--than NASA crews will be allowed to accept, but there's some upper bound on that. 

2) Early LSS-based private missions take about 15 tanker launches,² with propulsive return to LEO.  If you figure an LSS is good for four missions and costs about $300M, and a tanker launch's price (not cost) is about $20M, and an F9/D2 can be done for $200M (a pretty steep discount from where we are today), that's a $575M mission.  For a crew of 7, that's $80M/seat.  But if you launch two D2's for a crew of 14, that's a $775M mission, which works out to about $60M/seat.

3) AFAICT, nobody on this or any other thread has an answer to reducing the risk of hypersonic entry other than making it work.  And if you don't have to land, the profusion of failure modes is cut way down.  So, assuming that entry works reliably before landing does, if you can make an LSS variant that's capable of single-pass aerocapture, that 15 tanker launches drops to about 11.  You still need the two D2s, but that takes you down to $50M/seat, which is... kinda awesome.

If you can do even some of these, then I suspect that you can get at least 10 years using D2s to serve an LSS, and that's long enough to have a definitive Starship PRA, which in turn will tell you if reliability work alone will get you to a viable crewed system.

______________
²It's come to footnotes for the footnotes:  I'm assuming that you can't have crews doing refueling in HEEO, so these numbers are for a full top-off in VLEO and a post-ascent refueling in NRHO.  (NRHO turns out to be close to the sweet spot between excessive prop overhead for the tanker and prop economy for the LSS.) If you can get HEEO to work, you're down to 12 tankers.  I'm also assuming 150t to LEO for each tanker.

[JayWee]

I'd think that CCP systems have escape because STS was deemed, in retrospect, to have an unacceptably high pLOC (~1/100), and escape for a traditional stack is a pretty cheap way of reducing pLOC. 

Btw, it's interesting to point out that the original D2 plan was to use the SuperDracos primarily for land landing, with additional abort capability. So it wasn't a "mostly-unused" system.

[Lee Jay]

And "reasonably flat land" isn't as common as you think.

and runways are all over the place.

Reasonably flat land is at least as common as runways

Runways are reasonably flat, if you can land a spaceplane you can land vertically. 

That assumes you can steer to reasonably flat land.  SS has very little cross range.  A space plane can steer to a runway because it has enormous cross range - in the 1000km range.

[chopsticks]

And "reasonably flat land" isn't as common as you think.

and runways are all over the place.

Reasonably flat land is at least as common as runways

Runways are reasonably flat, if you can land a spaceplane you can land vertically. 

That assumes you can steer to reasonably flat land.  SS has very little cross range.  A space plane can steer to a runway because it has enormous cross range - in the 1000km range.

What is the cross range of SS? It's a lot more than a capsule, but not as good as an airplane.

[DanClemmensen]

And "reasonably flat land" isn't as common as you think.

and runways are all over the place.

Reasonably flat land is at least as common as runways

Runways are reasonably flat, if you can land a spaceplane you can land vertically. 

That assumes you can steer to reasonably flat land.  SS has very little cross range.  A space plane can steer to a runway because it has enormous cross range - in the 1000km range.

I'm confused. First you say "there are runways all over the place", and now you say you need enormous cross range? A vertical lander can land on literally any runway including a grass strip. A shuttle-type lander can only land on certain long runways, so it might need that cross-range ability. But some failure modes will restrict its cross range.

Note: I agree the abort problem is hard, but let's try to agree on the parameters of the problem.

[Lee Jay]

And "reasonably flat land" isn't as common as you think.

and runways are all over the place.

Reasonably flat land is at least as common as runways

Runways are reasonably flat, if you can land a spaceplane you can land vertically. 

That assumes you can steer to reasonably flat land.  SS has very little cross range.  A space plane can steer to a runway because it has enormous cross range - in the 1000km range.

I'm confused. First you say "there are runways all over the place", and now you say you need enormous cross range?

Both.

If your ballistic trajectory will take you into an ocean or mountain range, a substantial cross range is a good thing - it'll get your to a runway.

A vertical lander can land on literally any runway including a grass strip.

If it can get to one which, lacking cross range is far from a sure thing.

[Lee Jay]

And "reasonably flat land" isn't as common as you think.

and runways are all over the place.

Reasonably flat land is at least as common as runways

Runways are reasonably flat, if you can land a spaceplane you can land vertically. 

That assumes you can steer to reasonably flat land.  SS has very little cross range.  A space plane can steer to a runway because it has enormous cross range - in the 1000km range.

I'm confused. First you say "there are runways all over the place", and now you say you need enormous cross range?

Both.

If your ballistic trajectory will take you into an ocean or mountain range, a substantial cross range is a good thing - it'll get your to a runway.

A vertical lander can land on literally any runway including a grass strip.

If it can get to one which, lacking cross range is far from a sure thing.

And "reasonably flat land" isn't as common as you think.

and runways are all over the place.

Reasonably flat land is at least as common as runways

Runways are reasonably flat, if you can land a spaceplane you can land vertically. 

That assumes you can steer to reasonably flat land.  SS has very little cross range.  A space plane can steer to a runway because it has enormous cross range - in the 1000km range.

What is the cross range of SS? It's a lot more than a capsule, but not as good as an airplane.

I suspect it isn't much, since it uses a drag-based, rather than lifting entry.  Remember it's suppose to fly broadside to the airflow, not like an airplane.

[Barley]

What is the cross range of SS? It's a lot more than a capsule, but not as good as an airplane.

You want to look at down range capacity as well, i.e. the total landing ellipse (or whatever shape it is)

I assume this is in the context of an abort from orbit, since this is the only case where unplanned cross range is needed.*  In that case you also need to look at down range options.  You are moving at 8km/s.  Even if you need to get on the ground NOW several hundred km of down range requires nothing but timing.  There are situations where ms count, but there are many more where a few minutes don't matter.


* An abort during launch should be preplanned, if necessary you arrange for suitable diversion landing points. If it's non-flat land send in the bulldozers months ahead of time.  If its non-land send in the drone ship. 

An abort during a planned landing is going to end up pretty much where you planned.  You might divert from LZ-1 to LZ-2 or the skid strip if someone parks a car on your destination (or some such idiocy), but this does not require much cross range and only minimal planning.