# Using large orbital launchers as sounding rockets. What are the opportunities and challenges?

Instead of launching a payload to orbit, consider one of the big launchers of today (like Atlas V, Ariane 5, Falcon 9, Proton) being used as a sounding rocket for astronomical observation purposes. Lifting its payload thousands of kilometers into space and then falling down to Earth within an hour or a few.

My presumptions:

• Compared to an orbital insertion, a sounding rocket mission would allow for much more payload mass since no acceleration to orbital velocity is needed.

• It would be easier for a reusable first stage to land.

• The design of the payload could be much simplified: A battery as power supply. No need for on board propulsion. No communication needed, the data collected could be landed as a physical memory chip. No radiation hardening needed for such a short exposure so the cheapest and latest off-the-shelf electronics could be used.

Sounding rockets do contribute alot to science already, so I wonder how it might be expanded to big sounding payloads. The payloads could either be discarded after their one and only use (as in making one observation of e.g. an exoplanet when it is known to transit), or be soft landed and upgraded and reconfigured for another mission.

Why aren't sounding rockets made as large as orbital launchers? Are there show stoppers here? For example that orbital launchers are ill suited for sounding missions. Or that there aren't as many simplifications to be made on the payload as I suggest here. Or that the science opportunities don't motivate say $100,000,000 for one or two hours of observation above the atmosphere. • What kind of payload are you thinking of? Microgravity physics experiments tend to be small and more economically piggy-back to the ISS. Astronomical purposes could be much more economical from a stratospheric balloon if being above 99.9% of the atmosphere is enough. For in-situ mesospheric measurements the added height is not useful. – gerrit Jan 11 '17 at 14:29 • @gerrit I imagine for example a telescope at a wavelength of light that is absorbed by the atmosphere. With mass constraints relaxed it might be made big and cheap. Using only a few tens of tons of steel reinforced concrete to keep its shape stable. – LocalFluff Jan 11 '17 at 15:14 • Stratospheric balloons are used routinely for sub-mm astronomy, as being above 99.9% of the atmosphere and essentially 100% of the water vapour is quite cost-effective. At what wavelength does the part of the atmosphere above 30 km pose a major hinder? – gerrit Jan 11 '17 at 15:28 • @gerrit So why aren't balloons used more? Maybe because they cannot take tens of tons of payload mass? – LocalFluff Jan 11 '17 at 16:01 • Balloons are used a lot for payloads up to several thousand kg, which allows for a lot of interesting science. There are plenty of balloon questions on the site that address the limitations. – gerrit Jan 11 '17 at 16:21 ## 1 Answer Suborbital sounding rockets cost about 1/100 as much as an orbital launcher. Black Brant XII, one of the most advanced sounding rockets in use, can take 100-400kg payload into space for \$600K.

For a Falcon-9-based sounding rocket approach to make any sense, you'd have to describe a single payload that delivered as much science as 100 individual 100kg payloads. I'm hard-pressed to imagine such a thing.

Even a single-stage, fully-reusable Falcon 9 isn't likely to drive launch costs low enough to compete with that. I would guess that the single-launch staffing, logistics, fuel, and refurbishment costs would pay for ten Black Brants -- and SpaceX hasn't yet demonstrated any reusability.