Momentus Space

[Ronsmytheiii]

Today we are excited to announce the details of our seed funding. Momentus provides in-space transportation services for satellites between various orbits out to deep space. Our mission is to provide the most efficient in-space transportation services powered by deep space resource utilization, and the individuals and organizations outlined below will help us achieve our goal.

We would like to especially thank Prime Movers Lab, who led the $8.3M round, with participation from Liquid 2 Ventures, One Way Ventures, Mountain Nazca, Y Combinator, and numerous others.

Momentus has not only developed groundbreaking and efficient water-powered, in-space rockets, but also validated the massive market demand for their services with hundreds of millions of dollars in LOIs.

Interesting company, looks like they are developing a water based in-space tug.

https://momentus.space/2018/11/14/proudly-announcing-8-3m-in-seed-funding/

[momerathe]

God their website is annoying. "Just tell me the facts, ma'am."

Anyway, 700 seconds seems.. okay, I guess? I mean, it's an order of magnitude less than SEP is capable of, but I suppose they've traded-off for higher T/W, which is a legitimate concern if you're going to spend a lot of time climbing in and out of gravity wells.

I would like to see some considerably more detailed numbers, though.

[Asteroza]

Of note, Orbit Fab is going to do water tanker testing at ISS (inside?), so there is that interesting interplay between orbital propellant depots, tankers, and customer sats with water fueled propulsion.

[TrevorMonty]

Today we are excited to announce the details of our seed funding. Momentus provides in-space transportation services for satellites between various orbits out to deep space. Our mission is to provide the most efficient in-space transportation services powered by deep space resource utilization, and the individuals and organizations outlined below will help us achieve our goal.

We would like to especially thank Prime Movers Lab, who led the $8.3M round, with participation from Liquid 2 Ventures, One Way Ventures, Mountain Nazca, Y Combinator, and numerous others.

Momentus has not only developed groundbreaking and efficient water-powered, in-space rockets, but also validated the massive market demand for their services with hundreds of millions of dollars in LOIs.

Interesting company, looks like they are developing a water based in-space tug.

https://momentus.space/2018/11/14/proudly-announcing-8-3m-in-seed-funding/

God their website is annoying. "Just tell me the facts, ma'am."

Anyway, 700 seconds seems.. okay, I guess? I mean, it's an order of magnitude less than SEP is capable of, but I suppose they've traded-off for higher T/W, which is a legitimate concern if you're going to spend a lot of time climbing in and out of gravity wells.

I would like to see some considerably more detailed numbers, though.

I couldn't find 700 sec just x3 more than chemical.
Best I've seen for water propulsion is in 300s ISP, for solar concentrator system that super heats water.

 Still 700s is respectable if combined with moderate thrust. If they can do LEO - GEO in weeks not months of SEP then could be onto winner.

Maybe able to use it for lunar landers with power beaming to lander by laser or microwave.

[ncb1397]

I couldn't find 700 sec just x3 more than chemical.

If you mean you couldn't find a reference to 700 seconds, it is on their website:

Ardoride:

500-1250 KG WET MASS
180 KG PAYLOAD TO LUNAR ORBIT FROM LEO
250 KG PAYLOAD TO MARS ORBIT FROM GTO
UP TO 6 KM/SEC ∆V
2-3 KW SOLAR PANELS
SPECIFIC IMPULSE UP TO 700 SEC

Vigoride:

STARTING MASS 180 KG (ESPA)
OR 300 KG (ESPA GRANDE)
UP TO 6 KM/SEC ∆V
500 W SOLAR PANELS
SPECIFIC IMPULSE UP TO 700 SEC

https://momentus.space/services/

[Robotbeat]

6km/s delta-v is a lot for a tiny spacecraft. If it takes its time, doing burns at perigee, it should be able to easily put itself in orbit around Mars even if it starts in LEO. That small one, Vigoride, should be capable of launch on Rocketlab's Electron with a 30kg payload all the way to Mars orbit.

Kinda neat to do a Mars orbiter with a launch of just $6 million (dunno the cost of Vigoride, tho), either as a Spaceflight Services Rideshare or Rocketlab. And soon a bunch of other providers for probably even cheaper (I think India has cheaper rideshares?), including from the ISS (via Nanoracks' new Bishop Airlock launching in 11 months on CRS-19 can handle 300kg microsats like this, so the full 61kg of payload to Mars orbit).

...the latter option is kind of interesting as you could just launch water anytime a Dragon or Cygnus launch is volume-limited. Using ISS as a sort of ad hoc propellant depot.

[ncb1397]

It would be an interesting technology to look into for human Mars missions. You essentially have the propellant mass fractions of dense non cryogenic propellants with the ISP of nuclear thermal(700-900 seconds), but with more easily accommodated power requirements than with higher ISP electric propulsion and no radiological issues. You also have commonality between life support(O2 and water) and fuel, with the ability to dynamically trade one for the other.

[catdlr]

For those wanting to subscribe to any videos from them:

MOMENTUS

[Asteroza]

...the latter option is kind of interesting as you could just launch water anytime a Dragon or Cygnus launch is volume-limited. Using ISS as a sort of ad hoc propellant depot.

That's an interesting thought, relative to Orbit Fab and their water tanker testing to be done at ISS, and in the context of Jon Goff's 3 burn departure concept, which allows start at ISS orbit. By definition the propulsion stages need to be long lived for electric propulsion, though there is the deviation from the original 3 burn concept (refuel an existing upper stage for first burn).

[momerathe]

Ardoride:

500-1250 KG WET MASS
180 KG PAYLOAD TO LUNAR ORBIT FROM LEO
250 KG PAYLOAD TO MARS ORBIT FROM GTO
UP TO 6 KM/SEC ∆V
2-3 KW SOLAR PANELS
SPECIFIC IMPULSE UP TO 700 SEC

Let's plug in some numbers. Assuming an overall system efficiency of 50% (just a ballpark figure obviously), that gives a mass flow rate of

(3000*0.5)/(0.5*(700*9.8 )^2) = ~60 mg/s

and a thrust of ~0.4 N.

Plugging the maximum wet mass and delta-v into the rocket equation, gives a maximum dry mass of ~520kg (presumably including extra tankage, which is why it's above the minimum listed wet mass), and thus a fuel mass of 730 kg.

Combining the two gives a maximum burn time of ~140 days.

One question I would have is whether this thrust is high enough to get meaningful benefit from the oberth effect.. you would require many perigee burns. According to wikipedia, the delta-v required for LEO to Lunar orbit is 8km/s for a continuous burn spiral trajectory..



 

[TrevorMonty]

For those wanting to subscribe to any videos from them:

MOMENTUS

Spacecraft looks lite, donut fuel tank, arrays and propulsion.

[momerathe]

So, because I can't leave well-enough alone, I decided to poke into the code that's driving the "mission calculator" on their website.

here's the salient parts: https://pastebin.com/eNWnqiAD

Things to note:
For the Adoride they're using Isp of 800 seconds, not 700.
Mass flow rate is ~195 mg/s (> triple my estimate). Together that makes a jet power of ~6kw. So barring magic, the figure of 2-3kw from the solar panels must be per panel, with multiples installed. Thrust would be 1.5N.

On second thoughts, I'm not sure. There's a weird factor of 10 multiplying the burn time at the end of the calculation, so maybe the mass flow rate is a tenth of what's listed in "h"? That would drop the jet power to 600W and thrust to 0.15N. Assuming 2-3kWe, that gives an overall system efficiency of 20-30%.

Dry mass = 105 kg ex tankage + 7.5 kg per tank. Each tank (max 6) has a 90kg propellant capacity. Based on this they could actually go much higher that 6km/s delta-v if they wanted, by reducing the payload mass.

One thing to note: the delta-v numbers they're using for different destinations are the standard ones you see listed for impulsive trajectories. As I said before, I'm not sure how well this assumption holds up.


Overall, I'm more convinced of this concept now than I was when I started digging. Assuming they don't blow their mass budget, of course. I would love to see more details of their thruster, and what TRL it's at.

[ncb1397]

The weird factor of 10 probably means it only will thrust ~10% of the time. The 6 KW power requirements for the ISP and mass flow rate probably means there is a couple KWh battery (3 KWh is probably on the order or 15 kg) that provides an extra couple KW for an hour or so. Thrusting is then done during perigee which explains the near chemical delta-v numbers for orbit transfers.

[momerathe]

Maybe? ¯\_(ツ)_/¯

I wish they'd just tell us. It's not as if anyone's going to spend money on this without knowing the details..

[momerathe]

A recent-ish journal article on a very similar looking propulsion technology: The microwave electro-thermal (MET) thruster using water vapor propellant

Differences are that the linked article describes a magnetron rather than a helicon antenna as a microwave source, but the Isp and power levels line up - even down to the description of using a vortex for plasma containment.

[jongoff]

...the latter option is kind of interesting as you could just launch water anytime a Dragon or Cygnus launch is volume-limited. Using ISS as a sort of ad hoc propellant depot.

That's an interesting thought, relative to Orbit Fab and their water tanker testing to be done at ISS, and in the context of Jon Goff's 3 burn departure concept, which allows start at ISS orbit. By definition the propulsion stages need to be long lived for electric propulsion, though there is the deviation from the original 3 burn concept (refuel an existing upper stage for first burn).

Yeah, if you were leaving from ISS with a low-thrust system like this, there are different maneuvers you would do than the 3-burn departure. I've seen some good papers on the tricks you can do for a low-thrust hyperbolic departure.

~Jon

[Tywin]

Vigoride is ready for commercialization...

https://www.spaceconnectonline.com.au/r-d/3176-us-space-start-up-enters-space-race-with-water-powered-satellites

[Davidthefat]

What's stopping Rocket Lab from expanding the capabilities of the kick stage, and effectively do what this company is trying to do by marketing it? Curie has the flight heritage under its belt.

[Robotbeat]

What's stopping Rocket Lab from expanding the capabilities of the kick stage, and effectively do what this company is trying to do by marketing it? Curie has the flight heritage under its belt.

....because Rocketlab's kick stage Isp is much lower. And dry mass fraction probably worse as well.

[vaporcobra]

What's stopping Rocket Lab from expanding the capabilities of the kick stage, and effectively do what this company is trying to do by marketing it? Curie has the flight heritage under its belt.

Electron's performance. 150–225 kg to LEO leaves almost zero margin for hardware that isn't payload. Vigoride will weigh no less than 80 kg wet per Momentus' website, meaning that the limits of Electron would be ~140 kg to a 700 km elliptical orbit with Vigoride providing a max of 1 km/s dV (for a 50 kg payload) from there. That is by no means shabby but it's really hard to conceive of more than a tiny handful of customers for something like that.