ARCA Expendable Smallsat SSTO

[sevenperforce]

This had been discussed on the forums a few years ago, but now ARCA (a rather odd company that doesn't seem to know what its market is) has released a glitzy CGI video of its "Haas 2CAJ" smallsat SSTO launcher. While the company's track record isn't very good, the combination of technologies and solutions in their idea seems solid enough.

Here's a bunch of specs on it.

It's a 16-meter-high smallsat SSTO burning RP-1 and HTP with a projected payload of 100 kg to LEO, using a rather large linear aerospike engine and a composite frame/tank with common bulkheads. Claimed launch price is just $1 million.

As these things go, it's not a bad idea. HTP/RP-1 is about the only non-exotic prop combo with a higher impulse density than kerolox, and it also permits higher thrust than kerolox, which helps make up for the lower TWR of linear aerospike engines. It's pressure-fed, which would typically be the death knell for an SSTO, but since the linear aerospike engine doesn't require a high chamber pressure it's not a bad idea. Pressure-fed engines also typically have very poor tankage ratios, but the composite tanks can handle higher pressures. The pressurant is liquid helium that is passed through an engine heat exchanger, simultaneously cooling the big aerospike engine and saving on the weight of a turbopump, which further mitigates the low TWR of the aerospike.

The linear aerospike allows for roll, pitch, and yaw authority through differential throttling alone, which saves on the mass of a gimbal system. The use of HTP comes with its own set of handling challenges, but it is cheaper than LOX, requires no insulation, and requires less demanding materials specifications than LOX. All in all, not a bad concept. Whether they will pull it off or not, I don't know.

They fuss and fret over the horrors of staging, but honestly this could be very competitive if it was offered with the option of COTS parallel SRBs. Base configuration for smallsats, a couple of SRBs for larger LEO comsats, or a quad of SRBs for big LEO comsats or GTO smallsats. Better than trying to fuss with a second stage.

Edited April 3, 2017 by sevenperforce
metric/imperial mixup

[Steel]

Not to get onboard the hype train too early, but this is a really interesting concept.

Obviously the jury is out until they actually show some hardware, but I like the basics! As an Englishman the RP-1/HTP is a great fuel mix (we miss you, Black Arrow) and it would be really cool to actually see someone test out the benefits of aerospike engines that have been thrown around the scientific community and the internet for so long now.

[Stone Blue]

Interesting concept...

Just a note, did you mean 5point3 meters?... or maybe 53FEET tall??... Thats certainly not close to ~160ft in the vid... unless thats just a "proof of concept" example... but then, that still seems REALLY tall for just a 100kg payload... ??

[sevenperforce]

8 minutes ago, Stone Blue said:

Just a note, did you mean 5point3 meters?... or maybe 53FEET tall??... Thats certainly not close to ~160ft in the vid... unless thats just a "proof of concept" example... but then, that still seems REALLY tall for just a 100kg payload... ??

Whooooops! 16 meters. 53 feet. I meant to put it in metric but I put the Imperial number instead.

12 minutes ago, Steel said:

Not to get onboard the hype train too early, but this is a really interesting concept.

Obviously the jury is out until they actually show some hardware, but I like the basics! As an Englishman the RP-1/HTP is a great fuel mix (we miss you, Black Arrow) and it would be really cool to actually see someone test out the benefits of aerospike engines that have been thrown around the scientific community and the internet for so long now.

Yeah, avoiding the hype train is a good idea; this company has produced a lot of odd concepts in the past without a lot of consistency. Like, they made a tiny $700 electric skateboard and a $19,000 ducted-fan hoverboard. So...I'm not really sure what they're up to.

But you're right, the basics seem good. If you're going to go for a pure-rocket expendable SSTO then it needs to be simple, cheap, and reliable while simultaneously taking advantage of every last drop of TWR and ISP savings it can get. "Cutting-edge" and "simple/cheap" don't often play well together. But composite tanks, room-temperature propellants, and a regenerative pressure-fed linear aerospike are all readily achievable tech that cross-enable. Plus, HTP is hypergolic with RP-1 so that makes it even simpler.

And I think the linear aerospike is definitely a better way to go than a toroidal aerospike. Not only does it permit regenerative cooling with cheaper, lighter-weight materials, but it natively enables thrust vectoring and roll control via differential thrust, which a single-chamber toroidal aerospike completely lacks.

[sevenperforce]

This sort of launch vehicle would play very, very well with air augmentation, too. Just a simple aluminum panel stretched across the face of each aerospike would cost very little while boosting thrust and ISP nicely.

EDIT: Here are some additional specs....

Length: 16 m

Diameter: 1.5 m

Dry mass: 550 kg

Launch mass: 16,290 kg

Payload mass: 100 kg

Engine: Pressure-fed linear aerospike

Nozzle: 80:1 expansion ratio, 80% cut

Engine coolant & pressurant: Liquid helium

Number of chambers: 16

Nozzle cooling: Ablative + RP-1 film

Propellant: HTP + RP-1

Burn duration: 272 s

Thrust (SL): 22,920 kgf

Thrust (vac): 33,500 kgf

Isp (SL): 230 s

Isp (vac): 314 s

Propellant flow rate: 100 kg/s

Mixture ratio: 7.46:1

Tank pressure: 20 barg

Chamber pressure: 16 barg

Edited April 3, 2017 by sevenperforce

[sevenperforce]

Of note: the claimed dry mass ratio is just 12% more than that of the ITS Tanker, which is pushing every envelope, has higher TWR engines and a lower vehicle TWR, and benefits hugely from the square-cube law. Then again, HTP is denser than LOX, which should help ARCA somewhat, and the ARCA vehicle wouldn't need TPS or RCS systems like the ITS Tanker.

Hitting that dry mass would be tough.

[Nothalogh]

5 hours ago, sevenperforce said:

This sort of launch vehicle would play very, very well with air augmentation, too.

I too, wish for Gnom to ride again

3 hours ago, sevenperforce said:

Of note: the claimed dry mass ratio is just 12% more than that of the ITS Tanker, which is pushing every envelope, has higher TWR engines and a lower vehicle TWR, and benefits hugely from the square-cube law. Then again, HTP is denser than LOX, which should help ARCA somewhat, and the ARCA vehicle wouldn't need TPS or RCS systems like the ITS Tanker.

Hitting that dry mass would be tough.

It's silly to try for full SSTO in my opinion.

A high performance low mass smallsat launcher with no cryo means you could effectively have a mobile launch facility.

Yes, this has all kinds of weapons implications, but it also makes launches to particular inclinations as efficient as possible, since your launch is from wherever you can drive to

[insert_name]

um why was the whole booster trying to dock with the ISS?

[kerbiloid]

7 minutes ago, insert_name said:

um why was the whole booster trying to dock with the ISS?

The booster is approaching to ISS in retrograde position.
It hasn't been launched in the opposite direction, as their relative speed is tiny.
It couldn't rotate without RCS.

That's ISS is trying to catch him before it deorbits.

[tater]

That's almost 4x more expensive than a new F9 per kg.

[Shpaget]

The video seems a bit dishonest.

Complexity and cost of multi stage blah blah... then the video of F9 RUD that had nothing to do with staging.

Lightweight composite materials... whoa! They're using those? Why did nobody else think of that?

The fact that all orbital vehicles we've ever built are multistage should be a good indication that there is a certain benefit of having them multistage, as opposed to SSTO.

Also, full throttle main engine while docking to ISS.

Edited April 4, 2017 by Shpaget

[Hypercosmic]

38 minutes ago, Shpaget said:

The video seems a bit dishonest.

Complexity and cost of multi stage blah blah... then the video of F9 RUD that had nothing to do with staging.

Lightweight composite materials... whoa! They're using those? Why did nobody else think of that?

The fact that all orbital vehicles we've ever built are multistage should be a good indication that there is a certain benefit of having them multistage, as opposed to SSTO.

Also, full throttle main engine while docking to ISS.

1. "Complexity and cost of multi stage blah blah... then the video of F9 RUD that had nothing to do with staging." I facepalmed myself reading this statement. Do you really think this is the ONLY launch failure in the history of rocketry?

2. SpaceX has already tested its giant composite tank.

3. Play RO + RSS + FAR, then tell me if you manage to get into orbit with a SSTO. In the other note, Skylon is a SSTO spaceplane concept.

4. Wait, what?

[sevenperforce]

8 hours ago, insert_name said:

um why was the whole booster trying to dock with the ISS?

Because they had a little extra CGI budget and decided to add something nonsensical?

The website touted the benefits of having the "whole vehicle in orbit" and claimed that on-orbit refueling could allow it to do all kinds of BLEO stuff, but that's stupid. First, a vacuum specific impulse of 314 seconds isn't going to get you very far beyond LEO. Second, no one is going to launch a fuel tank just to refuel an unrelated booster. Third, any hypergolic second or third or fourth stage has as much capacity to be refueled on orbit as this "whole vehicle". Finally, the whole question is moot because the liquid helium pressurant tank would need to be filled on orbit, which ain't happening.

6 hours ago, Shpaget said:

The video seems a bit dishonest.

Complexity and cost of multi stage blah blah... then the video of F9 RUD that had nothing to do with staging.

The fact that all orbital vehicles we've ever built are multistage should be a good indication that there is a certain benefit of having them multistage, as opposed to SSTO.

I mean, technically the F9 RUD had to do with staging because, uh, the failure happened in one of the stages.

But yeah, it seems slightly dishonest and very pop-speculative.

At the same time, a pricetag of $1 million for a smallsat launch does beat out the current competition, even if it's not competitive with larger payloads. And a single-stage vehicle definitely can be launched from anywhere, which is one advantage.

Small launchers like these could really benefit from being trucked up to a high-altitude point and launched from there. 

5 hours ago, Hypercosmic said:

6 hours ago, Shpaget said:

Also, full throttle main engine while docking to ISS.

Wait, what?

That was just goofy.

12 hours ago, Nothalogh said:

I too, wish for Gnom to ride again

Fairly certain that any problems this concept might have with meeting its performance specs would be more than solved by going GNOM-style. And the parallel (pun intended) option of going with strap-on COTS SRBs would make it quite competitive if they'd relax their "SSTO is the awesomest" obsession.

Is the smallest LV to ever reach orbit the Lambda 4S?

[Shpaget]

9 hours ago, Hypercosmic said:

1. "Complexity and cost of multi stage blah blah... then the video of F9 RUD that had nothing to do with staging." I facepalmed myself reading this statement. Do you really think this is the ONLY launch failure in the history of rocketry?

2. SpaceX has already tested its giant composite tank.

3. Play RO + RSS + FAR, then tell me if you manage to get into orbit with a SSTO. In the other note, Skylon is a SSTO spaceplane concept.

4. Wait, what?

1. What are you talking about?

They clearly display the words I posted (granted, not verbatim) and the video of incident where F9 fell apart, implying that the cause of that incident is the complexity of multistage rockets.
And no, I do not think that's the only launch failure in the history of rocketry. Where did you get that notion? I commented on their choice to present that one particular failure as an example of what having multiple stages leads to.

2. We're not playing KSP. Whatever you think is or is not possible in KSP has nothing to do with this proposal or my comment about the way it is presented to the public. In fact, my comment does not even address the possibility of their, or any other SSTO proposal. I am commenting on the way they are misrepresenting the current state of multistage rockets and their place under the Sun.

3. So? How does that make ARCA's pitch any less dishonest?

4. Watch the video.

3 hours ago, sevenperforce said:

I mean, technically the F9 RUD had to do with staging because, uh, the failure happened in one of the stages.

But yeah, it seems slightly dishonest and very pop-speculative.

Of course. But one could make the same connection about rockets that have engines. As a matter of fact, every single rocket that failed during the launch had at least one engine. 

[sevenperforce]

15 minutes ago, Shpaget said:

4 hours ago, sevenperforce said:

10 hours ago, Shpaget said:

The video seems a bit dishonest.

Complexity and cost of multi stage blah blah... then the video of F9 RUD that had nothing to do with staging.

I mean, technically the F9 RUD had to do with staging because, uh, the failure happened in one of the stages.

Of course. But one could make the same connection about rockets that have engines. As a matter of fact, every single rocket that failed during the launch had at least one engine. 

I suppose they would say "well the failure happened in the stage that wasn't in use" which frankly doesn't make a lick of difference.

While we're at it, how about the failure of the COPV that took out AMOS-6? That was a failure of a helium pressurant tank inside a composite tank during fueling. Which, you know, is what ARCA is proposing we use. 

[Steel]

Right, let's calm this down a little bit!

11 hours ago, Shpaget said:

The video seems a bit dishonest.

Complexity and cost of multi stage blah blah... then the video of F9 RUD that had nothing to do with staging.

Lightweight composite materials... whoa! They're using those? Why did nobody else think of that?

The fact that all orbital vehicles we've ever built are multistage should be a good indication that there is a certain benefit of having them multistage, as opposed to SSTO.

Also, full throttle main engine while docking to ISS.

I'm not sure about dishonest, let's just call it ambitious!

They used the F9 video (presumably) because it some of the is the best footage ever of a rocket having a RUD (without any lives lost). They don't call it out it as a SpaceX flight and at the end of the day only a very few people (mostly in internet forums like this) will even know it was an F9.

I think @Hypercosmic missed your sarcasm for part 2!

11 hours ago, Hypercosmic said:

...

2. SpaceX has already tested its giant composite tank.

...

But (to me at least) it doesn't seem like they're being in any way dishonest when talking about composites. They don't claim that they're the first or that they are the only ones doing it (though they would be one of only a few), and it does make a huge amount of sense from an engineering point of view.

Indeed there is a huge benefit to staging, but there are also benefits to SSTO (i.e simplicity, elegance, cost & time to build). At the end of the day the two approaches are aimed at different markets, these guys are not aiming for heavy lift, where staged rockets are still the way to go by a huge margin.

Yeah the bit with the ISS is a bit silly. But these guys are not pitching to us, they're pitching to investors who don't have a clue how to dock to the ISS!

 

Edited April 4, 2017 by Steel

[sevenperforce]

47 minutes ago, Steel said:

Indeed there is a huge benefit to staging, but there are also benefits to SSTO (i.e simplicity, elegance, cost & time to build). At the end of the day the two approaches are aimed at different markets, these guys are not aiming for heavy lift, where staged rockets are still the way to go by a huge margin.

Elegance counts for nothing; if hanging Chick-fil-A sandwiches on the sides of rockets decreased drag, rocket engineers would make CFA runs before every launch.

Pulling off an expendable SSTO for smallsats is a noble goal, if the money works out.

1 hour ago, Steel said:

Yeah the bit with the ISS is a bit silly. But these guys are not pitching to us, they're pitching to investors who don't have a clue how to dock to the ISS!

And that means they are either stupid or dishonest. If they don't know that their vehicle doesn't have this capability, they are flatly stupid. If they do know that this vehicle doesn't have this capability, they are trying to trick their investors, which is dishonest.

[Steel]

4 minutes ago, sevenperforce said:

Elegance counts for nothing; if hanging Chick-fil-A sandwiches on the sides of rockets decreased drag, rocket engineers would make CFA runs before every launch.

Yeah ok, the elegance thing was tenuous, but the point still stands that SSTOs do have advantages over staged rockets in some aspects.

5 minutes ago, sevenperforce said:

And that means they are either stupid or dishonest. If they don't know that their vehicle doesn't have this capability, they are flatly stupid. If they do know that this vehicle doesn't have this capability, they are trying to trick their investors, which is dishonest.

Considering this thing is little more than a concept at the moment, whatever capability they claim it will have is what we have to take. If they want to say that in future they want to develop it so that it can dock to the ISS then that's fine.

[Streetwind]

...Yeah, that video is laying on the bovine excrement in some respects. But then again, most space-related PR videos seem to do so. I don't actually mind the concept as such - it's an interesting mix of nonstandard technologies that could very well work out for them. And the thing about SSTOs is that, well... if you don't share the idea that staging is horrible, you don't actually have to use it as a SSTO. See, if I was a customer trying to launch a satellite to a higher orbit than this rocket is nominally capable of, I could consider buying some off-the-shelf solid ullage motors or hydrazine pencil thrusters, mounting them on some sort of ejectable adapter, and suddenly I have a jury-rigged second stage. Even 500 m/s goes a long way when you're already in orbit, and you don't need to dedicate much mass - just 20 kg out of your 100 kg allowance will do it with a 230s Isp. Perhaps by the time this rocket flies you can get some of those newfangled hydroxylammonium nitrate blends instead for an extra 20-30s, and perhaps you can add 10kg extra total mass if you accept a lower initial parking orbit, and you're already above 810 m/s.

That sounds a bit much in terms of effort when you could just choose a more capable smallsat launcher that puts your payload directly into your target orbit without making you worry about having to provide your own propulsion. But the thing is: $1 million for a 100 kg launch is a really, really good deal, even if you assume a low altitude, low inclination LEO. That's just $10,000 per kg. There are currently three what I would call "credible contenders" for smallsat launchers becoming operational before 2020, and they all cost more than that. Electron is $33,000 per kg to a 500km sun-synchronous orbit, which probably equates to a mid 20k's price for equatorial LEO. Vector Space Systems asks around $23,000 per kg for a ride to an unspecified "low inclination orbit". Virgin's LauncherOne meanwhile requests "less than" $50,000 per kg to an unspecified sun-synchronous orbit, and "less than" $43,000 per kg to an unspecified equatorial LEO.

Even if you contend that most of these companies, including ARCA, don't specify their target orbit exactly and that this can have a large influence on the payload you can launch for the given price of the vehicle, that's a staggering difference. Can ARCA really save that much money through ditching staging? I'm honestly not sure. Maybe that $1 million is the price of the launch vehicle alone, just like SpaceX advertises the price of the Falcon 9 by itself and conveniently neglects to mention that it's about the same amount again for the launch campaign to go with it. If the customer paid about $2 million for a 100kg launch in total, then that would put the Haas 2CA into very similar territory with most of the other small launchers, and would IMHO make it more believable. But we'll see in 2018, I guess.

 

On 4.4.2017 at 6:52 AM, tater said:

That's almost 4x more expensive than a new F9 per kg.

This is called economies of scale. All large launchers are cheaper in terms of price per kg than all smallsat launchers - that's just how physics favors larger rockets over smaller ones. However, customers are generally very willing to pay the markup in return for being able to launch on their own time, going to their own orbit, and without making compromises to their spacecraft to protect the primary payload of a larger launcher. Additionally, the price difference often isn't as pronounced in practice as it looks at first (see my comment re: Falcon 9 pricing in the paragraph above).

 

23 hours ago, Hypercosmic said:

2. SpaceX has already tested its giant composite tank.

Rocket Lab is about to launch a full composite orbital rocket, possibly as soon as this month even.

 

Edited April 5, 2017 by Streetwind

[tater]

Yeah, but what is the market for <100kg sats that are persnickety about not sharing a LV?

[Streetwind]

Stuff that Planet does, for starters, which has been speaking very favorably of dedicated smallsat launchers in various interviews (bottom few questions). They and three other companies plan as many as 1400 new smallsats over the next decade, and when you count all the smaller players too, that number more than doubles again. Some of those will be launched in bulk by large rockets, but all of the companies I mentioned in my post above already have a minimum of half a dozen launches booked even when they've never flown a single launch vehicle. Rocket Lab is starting to look stuffed full, even.

[tater]

With that many, wouldn't they be more like cubesats? I would assume in polar orbits (sun-synchronous, to be specific), as well. Seems like bulk launching at lower cost would be preferable, vs a custom launch of just a few (presumably with a bus).

Edited April 5, 2017 by tater

[sevenperforce]

7 hours ago, Streetwind said:

And the thing about SSTOs is that, well... if you don't share the idea that staging is horrible, you don't actually have to use it as a SSTO. See, if I was a customer trying to launch a satellite to a higher orbit than this rocket is nominally capable of, I could consider buying some off-the-shelf solid ullage motors or hydrazine pencil thrusters, mounting them on some sort of ejectable adapter, and suddenly I have a jury-rigged second stage. Even 500 m/s goes a long way when you're already in orbit, and you don't need to dedicate much mass - just 20 kg out of your 100 kg allowance will do it with a 230s Isp. Perhaps by the time this rocket flies you can get some of those newfangled hydroxylammonium nitrate blends instead for an extra 20-30s, and perhaps you can add 10kg extra total mass if you accept a lower initial parking orbit, and you're already above 810 m/s.

That sounds a bit much in terms of effort when you could just choose a more capable smallsat launcher that puts your payload directly into your target orbit without making you worry about having to provide your own propulsion. But the thing is: $1 million for a 100 kg launch is a really, really good deal, even if you assume a low altitude, low inclination LEO. That's just $10,000 per kg. There are currently three what I would call "credible contenders" for smallsat launchers becoming operational before 2020, and they all cost more than that.

Yeah, any comsat will have its own maneuvering bus already, so asking the bus manufacturer to squeeze in some extra dV at the expense of a slightly smaller terminal payload would allow GTO payloads, albeit while sacrificing some of the rapidity of the launch platform while you spiral out.

Using various configurations of strap-on COTS SRBs would be an even better way to squeeze some variable performance out of the launcher. If it didn't have a vacuum-optimized nozzle on the core stage, this wouldn't work, but it does, so...why not?

[Exoscientist]

On 4/3/2017 at 3:05 PM, sevenperforce said:

This had been discussed on the forums a few years ago, but now ARCA (a rather odd company that doesn't seem to know what its market is) has released a glitzy CGI video of its "Haas 2CAJ" smallsat SSTO launcher. While the company's track record isn't very good, the combination of technologies and solutions in their idea seems solid enough.

Here's a bunch of specs on it.

...

As these things go, it's not a bad idea. HTP/RP-1 is about the only non-exotic prop combo with a higher impulse density than kerolox, and it also permits higher thrust than kerolox, which helps make up for the lower TWR of linear aerospike engines. It's pressure-fed, which would typically be the death knell for an SSTO, but since the linear aerospike engine doesn't require a high chamber pressure it's not a bad idea. Pressure-fed engines also typically have very poor tankage ratios, but the composite tanks can handle higher pressures. The pressurant is liquid helium that is passed through an engine heat exchanger, simultaneously cooling the big aerospike engine and saving on the weight of a turbopump, which further mitigates the low TWR of the aerospike.

...

  It's the pressure-fed that makes me doubtful. This requires heavy tanks to hold the highly-pressurized propellant, even if the tanks are composite. I'd like to see their propellant mass to empty tank mass before I believe it's possible.

 I do think SSTO's are doable and not even particularly hard when using turbo-fed engines:

The Coming SSTO's.

http://exoscientist.blogspot.com/2012/05/coming-sstos.html

 

 

  Bob Clark

 

[sevenperforce]

7 minutes ago, Exoscientist said:

  It's the pressure-fed that makes me doubtful. This requires heavy tanks to hold the highly-pressurized propellant, even if the tanks are composite. I'd like to see their propellant mass to empty tank mass before I believe it's possible.

 I do think SSTO's are doable and not even particularly hard when using turbo-fed engines.

Easier to do a pressure-fed engine with composite tanks than with aluminum ones, simply because aluminum undergoes ductile deformation and composites don't.

Here are the claimed specs. Claimed empty mass is 550 kg and vacuum thrust is 329 kN, so if we guesstimate at a TWR of 100 on the linear aerospike engine, engine mass would be 229 kg, leaving a tankage and systems mass of 321 kilograms for the ~16,000 kg of fuel.

I have a lot of love in my heart for the "smallest possible reusable SSTO" idea.