CCDev to CCiCAP to CCtCAP Discussion Thread

[baldusi]

As for the LASes: all previous launch aborts were solid tractors (or ejection seats).  Dragon and CST-100 are both liquid-fuelled pushers.  CST-100 depends on a LOX/ethanol engine, while Dragon uses a much simpler hypergolic system.

You're confusing the DreamChaser RCS to the CST-100 abort motor (which are already qualified and are hypergolic). BTW, DC abort motors are hybrid. And both Dragon and CST-100 use multiple abort motors exactly to have redundancy. I've never heard of multiple solids for abort. BTW, the requirement is only 90% of success rate for aborts.

[Oli]

As an astronaut I would certainly prefer the CST-100 parachute and airbag landing to hypergolic thruster landing. The Dragon may be able to make more precise landings though.

By the way, what is the Dreamchaser's solution to launch abort over the ocean, deploying floats? 

[Robotbeat]

People here seem to take it for granted that SpaceX will be around in five years. I sure hope they are, but there are no guarantees in this business.

This shoots both ways: Disqualifying SpaceX simply because they are furthest along in some ways risks losing what has been accomplished. Secondly, there shouldn't be a premature down-select to just SpaceX.

[Jim]

Testing at a variety of altitudes and air speeds, after experiencing the acceleration and vibration of suborbital launch.

And what is that going to accomplish?

[Kabloona]

  I also strongly suspect that they're going to be testing their launch abort / propulsive landing off a Grasshopper,

What does that accomplish?

Testing at a variety of altitudes and air speeds, after experiencing the acceleration and vibration of suborbital launch.

As they get past the hovering tests and want to go supersonic and suborbital, they'll probably want some kind of aerodynamic cap.  If that cap is a DragonFly, each Grasshopper flight can also be a Dragon test flight.

There are only two LAS tests that matter: abort from pad, and abort in flight at worst-case conditions (max g's or max Q). All other environments will be bracketed by those two extremes.

Abort from pad will be done without grasshopper, obviously. Abort in flight at worst-case conditions can only be done from F9.

Abort from GH would be pretty much pointless.

Edit: In your reply above, which you posted simultaneously to mine, you seem to conflate LAS testing with testing Dragon's propulsive landing system. Obviously there's some overlap, but topic was specifically LAS, and as Jim has said, there's no point doing LAS tests off GH.

Maybe SpaceX will want to practice more Dragon propulsive landings later, at which time it might make sense to fly off a GH. But for the near term, which to SpaceX means getting the LAS qualified, GH has no place in that test regimen.

[Jim]

Testing at a variety of altitudes and air speeds, after experiencing the acceleration and vibration of suborbital launch.

And what is that going to accomplish?

What kind of question is that?  It's testing.  You learn things and make things better.

To get to the stage where propulsive landing is accepted in routine cases, Dragon needs to be tested like a commercial passenger aircraft: hundreds of test flights, under a wide variety of conditions.  It doesn't need to go to orbit for most of those tests, but on many of them it does need to go higher than it can fly on its own power.

A very robust abort system would be a natural byproduct of this kind of flight testing.

At the same time, they need to fly many test flights of the reusable first stage, and learn how to quickly and affordably refuel and restack used stages.  It seems natural to start combining these operations at some point.

A.  There is little return in the additional testing.
b.  They aren't flying GH for the sake of accumulating flight time.  Once the landing test objectives are done, you will see it go away.
b.  quick turnaround is years away.  The vehicle is going horizontal after landing before going back to the pad.

[rcoppola]

Do you really think they will not be able to provide the best service for the best price? And do you really expect NASA and Congress to walk away from that scenario?

On the contrary I see SpaceX way in the lead which makes CST-100 and especially Dream Chaser extreme long shots and likely wasted efforts, sadly.

So what would you have done?  Award a non-compete single-source contract to SpaceX or whoever?  NASA tried to fast-forward with CCiDC but it didn't fly.  So we have competition between the remaining contenders.  Yes, it involves some "wasted effort", but competition always does.

The operative question is: Will that competition ultimately pay off in lower cost to the customer in the end?  The jury is still out, but let's cut NASA some slack as this is (for them) a new way of doing business.

No, not at all. I am in favor of maintaining competition as long as possible. And I applaud NASA for going down this route. However, competition was always just a means to an end. Competition in and of itself is not sustainable without enough companies to exist within a given sizable market to provide either downward pricing pressure or increased capabilities at competitive pricing or both. NASA can not currently provide that kind of scale on their own. They just don't have the funds or the needs to support both the development and utilization of 3 different Crew service providers.

Based on NASA's current funding profile, it now becomes a trade on capabilities and approximate costs of bringing at least one of these services to market now. Get the best, most affordable domestic capability you can as fast as you can. Bring others on-line later as funds and market conditions allow. Who's now and who's later? I guess we'll find out soon enough.

[Rocket Science]

As an astronaut I would certainly prefer the CST-100 parachute and airbag landing to hypergolic thruster landing. The Dragon may be able to make more precise landings though.

By the way, what is the Dreamchaser's solution to launch abort over the ocean, deploying floats? 

SNC has stated that DC has no black zones, so we would be talking RTLS, TAL or ATO. No need really to ditch, since they can throttle their hybrid rocket motors...

[Oli]

^

TAL? ATO?

I read something about crew bailout, which would be ok I guess.

The Dreamchaser is by far the coolest design, but I fear its also the most expensive to maintain.

[BrightLight]

^

TAL? ATO?

I read something about crew bailout, which would be ok I guess.

The Dreamchaser is by far the coolest design, but I fear its also the most expensive to maintain.

OK I'll bite -
The design of the HL-20 from the outset was for a reduced cost, low maintenance spacecraft (compared to Shuttle), the DC is an outgrowth and evolution of the HL-20, why do you feel that the DC will be the most expensive to maintain?

[Jim]

1.  I see no reason to believe they don't intend to fly unloaded or lightly loaded first stages all the way to space and on boost-back trajectories as part of the Grasshopper program.  These are natural steps on an incremental path toward their stated goals.

2.  CCiCAP manned orbital flight appears to also be years away, and going horizontal doesn't have to be incompatible with quick turnaround. 

1.  There is no need for GH to do such things, they will have stages from revenue producing flights to play with, like what they are doing on Cassiope.  GH is only for close in testing and not full flight envelope.

2.  Quick turnaround is much further way.

[Rocket Science]

^

TAL? ATO?

I read something about crew bailout, which would be ok I guess.

The Dreamchaser is by far the coolest design, but I fear its also the most expensive to maintain.

TAL, “Trans Atlantic Landing” if needed at any 7000’ runway. ATO “Abort To Orbit, including once around. Bailing out might prove tricky wearing pressure suits out of the two hatches with the CoG changes as the crew is departing. If it’s not on fire why bail out?

Yes, the refurbishing and turnaround is going to be interesting but SNC sees it as no problem...

[Oli]

^

So the trajectory is along the coast or something? Otherwise there is no guarantee it will reach a runway. Then the crew would have to bail out before hitting the water.

P.S. Ah those are shuttle abort modes . Well but the shuttle had a whole tank of fuel to boost back to the launch site.

[Zed_Noir]

^

TAL? ATO?

I read something about crew bailout, which would be ok I guess.

The Dreamchaser is by far the coolest design, but I fear its also the most expensive to maintain.

OK I'll bite -
The design of the HL-20 from the outset was for a reduced cost, low maintenance spacecraft (compared to Shuttle), the DC is an outgrowth and evolution of the HL-20, why do you feel that the DC will be the most expensive to maintain?

Figure the current hybrid engines will have issues. Don't believe there is much experience with them in space for extended periods. You basically rebuild the engines after every mission.

Then there is the external TPS with unknown refurbishment costs.

Until the Dreamchaser flies a few flights. All cost estimates are exactly that, estimates.

[LegendCJS]

^

TAL? ATO?

I read something about crew bailout, which would be ok I guess.

The Dreamchaser is by far the coolest design, but I fear its also the most expensive to maintain.

OK I'll bite -
The design of the HL-20 from the outset was for a reduced cost, low maintenance spacecraft (compared to Shuttle), the DC is an outgrowth and evolution of the HL-20, why do you feel that the DC will be the most expensive to maintain?

The HL-20 is a shape.  Details of a shape aren't really known to correlate all that much with cost.

[BrightLight]

^

TAL? ATO?

I read something about crew bailout, which would be ok I guess.

The Dreamchaser is by far the coolest design, but I fear its also the most expensive to maintain.

OK I'll bite -
The design of the HL-20 from the outset was for a reduced cost, low maintenance spacecraft (compared to Shuttle), the DC is an outgrowth and evolution of the HL-20, why do you feel that the DC will be the most expensive to maintain?

The HL-20 is a shape.  Details of a shape aren't really known to correlate all that much with cost.

I agree with you that shape and cost are probably poorly correlated however, the design of the HL-20 had maintenance and refurbishment "built-in" such as access panels, simple engine replacement etc. The DC went a step further with the TPS "slipper" system for  replacement of the lower section. These design choices should make the DC competitive, hopefully the DC will make it to flight so that the long-term costs of operation can be extrapolated.

[Jim]

Clunky-legged, single-engined Grasshopper 1.0 was for close in testing.  Grasshopper 1.1 apparently is for full flight envelope.

Far from it.  They will being doing things with FH boosters before GH is ready.

[Lars_J]

As an astronaut I would certainly prefer the CST-100 parachute and airbag landing to hypergolic thruster landing. The Dragon may be able to make more precise landings though.

By the way, what is the Dreamchaser's solution to launch abort over the ocean, deploying floats? 

SNC has stated that DC has no black zones, so we would be talking RTLS, TAL or ATO. No need really to ditch, since they can throttle their hybrid rocket motors...

I'll be very interested to see how DC will handle (or not handle) ditching in the ocean, if needed. Not as simple as it sounds, and parachutes will add weight. DC is a great shape for runway landings, but what about anywhere else?

[QuantumG]

I'll be very interested to see how DC will handle (or not handle) ditching in the ocean, if needed. Not as simple as it sounds, and parachutes will add weight. DC is a great shape for runway landings, but what about anywhere else?

I don't understand.. surely it would be as easy to ditch in the ocean as any other glider. Why would you want parachutes?

[Lars_J]

I'll be very interested to see how DC will handle (or not handle) ditching in the ocean, if needed. Not as simple as it sounds, and parachutes will add weight. DC is a great shape for runway landings, but what about anywhere else?

I don't understand.. surely it would be as easy to ditch in the ocean as any other glider. Why would you want parachutes?

Ditching ANY aircraft in the ocean is a very difficult endeavor and has a very high chance of going badly. And DC won't be the most nimble or slow kind of glider.

I could be wrong on this, but I thought that NASA did not consider a Shuttle ditching in the ocean to be a survivable event - and DC has similar slow speed handling characteristics, doesn't it?